diff --git a/20171109/es-20171109.pdf b/20171109/es-20171109.pdf
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diff --git a/20171109/es-20171109.tex b/20171109/es-20171109.tex
index 2ab58f85cecc457c753d8bf3b4960cb0fb41b180..00de850716866cf946deb15cbed875388e0d2e99 100644
--- a/20171109/es-20171109.tex
+++ b/20171109/es-20171109.tex
@@ -219,7 +219,7 @@
\medskip
- synchron
+ asynchron
\begin{itemize}
\item
\emph{keine\/} Taktleitung für Abgleich, wann Daten anliegen
@@ -306,9 +306,9 @@
seriell
\begin{itemize}
\item
- \newterm{MISO\/}: Master Out, Slave In
+ \newterm{MOSI\/}: Master Out, Slave In
\item
- \newterm{MOSI\/}: Master In, Slave Out
+ \newterm{MISO\/}: Master In, Slave Out
\item
\newterm{SCLK\/}: Taktleitung (Clock)
\item
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+ id="text1490"
+ y="212.11559"
+ x="236.01785"
+ style="font-size:12px;font-style:normal;font-weight:normal;fill:#000000;fill-opacity:1;stroke:none;stroke-width:1px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1;font-family:Bitstream Vera Sans"
+ xml:space="preserve"><tspan
+ y="212.11559"
+ x="236.01785"
+ id="tspan1492"
+ sodipodi:role="line">SCLK</tspan><tspan
+ id="tspan1494"
+ y="227.11559"
+ x="236.01785"
+ sodipodi:role="line">MOSI</tspan><tspan
+ id="tspan1496"
+ y="242.11559"
+ x="236.01785"
+ sodipodi:role="line">MISO</tspan><tspan
+ id="tspan1498"
+ y="257.11559"
+ x="236.01785"
+ sodipodi:role="line">SS</tspan></text>
+ <path
+ id="path3867"
+ d="M 236.82812,245.75 L 250.04687,245.75"
+ style="fill:none;fill-opacity:0.75;fill-rule:evenodd;stroke:#000000;stroke-width:1px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1" />
+ </g>
+ </g>
+</svg>
diff --git a/20171116/Telefon_t-sinus-700.jpg b/20171116/Telefon_t-sinus-700.jpg
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@@ -0,0 +1 @@
+../common/Telefon_t-sinus-700.jpg
\ No newline at end of file
diff --git a/20171116/Zeichen_123.pdf b/20171116/Zeichen_123.pdf
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index 0000000000000000000000000000000000000000..fdbc897227df059cfda790a16555e6e417682116
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+../common/Zeichen_123.pdf
\ No newline at end of file
diff --git a/20171116/a380.jpg b/20171116/a380.jpg
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+../common/a380.jpg
\ No newline at end of file
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\ No newline at end of file
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+../common/dsc_8208.jpg
\ No newline at end of file
diff --git a/20171116/es-20171116.pdf b/20171116/es-20171116.pdf
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index 0000000000000000000000000000000000000000..e0fd1fe2cfcc18f261509b849357bcab3db98942
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diff --git a/20171116/es-20171116.tex b/20171116/es-20171116.tex
new file mode 100644
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--- /dev/null
+++ b/20171116/es-20171116.tex
@@ -0,0 +1,2230 @@
+% es-20171116.pdf - Lecture Slides on Embedded Systems
+% Copyright (C) 2013, 2014, 2015, 2016, 2017 Peter Gerwinski
+%
+% This document is free software: you can redistribute it and/or
+% modify it either under the terms of the Creative Commons
+% Attribution-ShareAlike 3.0 License, or under the terms of the
+% GNU General Public License as published by the Free Software
+% Foundation, either version 3 of the License, or (at your option)
+% any later version.
+%
+% This document is distributed in the hope that it will be useful,
+% but WITHOUT ANY WARRANTY; without even the implied warranty of
+% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+% GNU General Public License for more details.
+%
+% You should have received a copy of the GNU General Public License
+% along with this document. If not, see <http://www.gnu.org/licenses/>.
+%
+% You should have received a copy of the Creative Commons
+% Attribution-ShareAlike 3.0 Unported License along with this
+% document. If not, see <http://creativecommons.org/licenses/>.
+
+% README: Bus-Systeme, evtl. Echtzeit
+
+\documentclass[10pt,t]{beamer}
+
+\usepackage{pgslides}
+\usepackage{rotating}
+\usepackage{tikz}
+\usepackage[obeyfamily=false,mathrm=mathsf,textrm=sffamily]{siunitx}
+
+\newrgbcolor{lightyellow}{0.95 0.85 0.0}
+\newrgbcolor{lightorange}{1.0 0.7 0.0}
+\newrgbcolor{lightgreen}{0.0 0.8 0.0}
+
+\newcommand{\underconstruction}{\vspace*{-5cm plus 1filll}%
+ \begin{picture}(0,0)
+ \put(9,1.3){\makebox(0,0)[b]{\includegraphics[width=1.5cm]{Zeichen_123.pdf}}}
+ \put(9,1.0){\makebox(0,0)[t]{\shortstack{Änderungen\\vorbehalten}}}
+ \end{picture}}
+
+\title{Vertiefung Systemtechnik\\Eingebettete Systeme}
+\author{Prof.\ Dr.\ rer.\ nat.\ Peter Gerwinski}
+\date{16.\ November 2017}
+
+\newcommand{\ItwoC}{I\raisebox{0.5ex}{\footnotesize 2}C}
+
+\begin{document}
+
+\newlength{\normalpdfpageheight}
+\setlength{\normalpdfpageheight}{\pdfpageheight}
+
+\maketitleframe
+
+\nosectionnonumber{Vertiefung Systemtechnik -- Eingebettete Systeme}
+
+\begin{frame}
+
+ \shownosectionnonumber
+
+ \begin{itemize}
+ \item[\textbf{1}] \textbf{Einführung}
+ \hfill\makebox(0,0)[br]{\raisebox{2.25ex}{\url{https://gitlab.cvh-server.de/pgerwinski/es.git}}}%
+ \item[\textbf{2}] \textbf{Einführung in Unix}
+ \item[\textbf{3}] \textbf{TCP/IP in der Praxis}
+ \item[\textbf{4}] \textbf{Bus-Systeme}
+ \begin{itemize}
+ \color{medgreen}
+ \item[5.1] Was sind Bus-Systeme?
+ \item[5.2] RS-232
+ \item[5.3] \ItwoC\ (TWI)
+ \item[5.4] SPI
+ \item[5.5] Beispiel: Benutzung des \ItwoC-Busses
+ \end{itemize}
+ \item[\textbf{6}] \textbf{Echtzeit}
+ \begin{itemize}
+ \color{medgreen}
+ \item[5.1] Was ist Echtzeit?
+ \item[5.2] Echtzeitprogrammierung
+ \color{orange}
+ \item[5.3] Multitasking
+ \color{red}
+ \item[5.4] Ressourcen
+ \item[5.5] Prioritäten
+ \end{itemize}
+ \vspace*{-\smallskipamount}
+ \item[\textbf{\dots}]
+ \underconstruction
+ \end{itemize}
+
+\end{frame}
+
+\setcounter{section}{3}
+\section{Bus-Systeme}
+\subsection{Was sind Bus-Systeme?}
+
+\begin{frame}
+ \showsection
+ \showsubsection
+
+ \begin{quote}
+ Ein Bus ist ein System zur Datenübertragung zwischen mehreren
+ Teilnehmern über einen gemeinsamen Übertragungsweg.
+% \color{gray}
+% Findet eine Datenübertragung zwischen zwei Teilnehmern statt, so
+% müssen die übrigen Teilnehmer schweigen, da sie sich sonst
+% gegenseitig stören würden. Umgangssprachlich werden mitunter --
+% oft aus historischen Gründen – auch Datenübertragungssysteme als
+% "`Bus"' bezeichnet, die technisch eigentlich eine andere
+% Topologie besitzen.
+
+ \medskip
+
+ \strut\hfill\url{https://de.wikipedia.org/wiki/Bus_(Datenverarbeitung)}
+ \end{quote}
+ Beispiele:
+ \begin{itemize}
+ \item
+ Computer kommuniziert mit Peripherie
+ \item
+ Computer kommunizieren (direkt) miteinander
+ \item
+ Prozessor kommuniziert mit externem Speicher
+ \item
+ Teile eines Prozessors kommunizieren miteinander
+ \end{itemize}
+\end{frame}
+
+\begin{frame}
+ \showsection
+ \showsubsection
+ Standard-Computer:
+ \begin{itemize}
+ \item
+ Einsteckkarten: PCI (und Vorgänger)
+ \item
+ Festplatten: SATA (und Vorgänger)
+ \item
+ USB, FireWire, \dots
+ \item
+ Ethernet, CAN-Bus, \dots
+ \item
+ WLAN, BlueTooth, IR, \dots
+ \item
+ PS/2, RS-232, Centronics
+ \end{itemize}
+
+ \medskip
+
+ Minimal-Hardware:
+ \begin{itemize}
+ \item
+ RS-232
+ \item
+ \ItwoC\ (TWI)
+ \item
+ SPI
+ \end{itemize}
+
+ \begin{onlyenv}<1>
+ \begin{picture}(0,0)
+ \put(5,1.5){\includegraphics[height=3cm]{motherboard-anschluesse.jpg}}
+ \end{picture}
+ \end{onlyenv}
+ \begin{onlyenv}<2>
+ \begin{picture}(0,0)(-1.3,-4)
+ \put(1.8,-4.9){\includegraphics[height=3.5cm]{kompassmodul-an-roboter.jpg}}
+ \put(6.1,-3.3){\includegraphics[height=4.5cm]{kompassmodul.jpg}}
+ \put(6.1,1.2){\makebox(0,0)[tr]{\tikz{\draw(0,0)--(-1.9,-3.6);}}}
+ \put(6.1,-3.3){\makebox(0,0)[br]{\tikz{\draw(0,0)--(-1.8,0.2);}}}
+ \end{picture}
+ \end{onlyenv}
+\end{frame}
+
+\begin{frame}[fragile]
+
+ \showsection
+ \showsubsection
+
+ \vspace*{-\bigskipamount}
+ \begin{tabbing}
+ \newterm{Punkt-zu-Punkt}\quad\=\kill
+ \newterm{seriell} \> jedes Bit einzeln übertragen\\
+ \newterm{parallel} \> mehrere Bits gleichzeitig\\[\smallskipamount]
+ \newterm{synchron} \> Abgleich über Steuerleitung: \newterm{Takt}\\
+ \newterm{asynchron} \> Abgleich über Zeitvereinbarungen\\[\smallskipamount]
+ \newterm{Punkt-zu-Punkt} \> genau zwei Teilnehmer\\
+ \newterm{busfähig} \> mehrere Teilnehmer, mit \newterm{Adressierung}
+ \end{tabbing}
+
+ \begin{itemize}
+ \item
+ \ItwoC: seriell, synchron, mit Adressierung
+ \item
+ RS-232: seriell, asynchron, Punkt-zu-Punkt
+ \item
+ RS-485, USB, CAN: seriell, asynchron, mit Adressierung
+ \item
+ SPI: seriell, synchron, Punkt-zu-Punkt oder mit Adressierung
+ \end{itemize}
+
+\end{frame}
+
+\subsection{RS-232}
+
+\begin{frame}
+ \showsection
+ \showsubsection
+
+ seriell
+ \begin{itemize}
+ \item
+ \newterm{TX\/}: 1 Leitung für Daten
+ \item
+ \newterm{RX\/}: ggf.\ 1 Leitung für Daten in der anderen Richtung
+ \item
+ \newterm{GND\/}: gemeinsame \newterm{Masse}
+ \item
+ evtl.\ zusätzliche Steuerleitungen
+ \end{itemize}
+
+ \medskip
+
+ asynchron
+ \begin{itemize}
+ \item
+ \emph{keine\/} Taktleitung für Abgleich, wann Daten anliegen
+ \item
+ Stattdessen: Abgleich über Zeitvereinbarungen
+ \arrowitem
+ Jeder Teilnehmer braucht eine eigene Zeitbasis.
+ \end{itemize}
+
+ \medskip
+
+ Punkt-zu-Punkt
+ \begin{itemize}
+ \item
+ nur 2 Teilnehmer vorgesehen
+ \end{itemize}
+\end{frame}
+
+\begin{frame}
+ \showsubsection
+ \vspace*{-0.35cm}
+ \begin{center}
+ \includegraphics[scale=0.9]{rs-232.pdf}
+ \end{center}
+\end{frame}
+
+\subsection{\protect\ItwoC\ (TWI)}
+
+\begin{frame}
+ \showsection
+ \showsubsection
+
+ \ItwoC\ = Inter-IC; TWI = Two-Wire-Interface
+
+ \medskip
+
+ seriell
+ \begin{itemize}
+ \item
+ \newterm{SDA\/}: 1 Leitung für Daten (in beiden Richtungen)
+ \item
+ \newterm{SCL\/}: Taktleitung (Clock)
+ \item
+ \newterm{GND\/}: gemeinsame Masse
+ \item
+ evtl.\ \newterm{VCC\/}: Stromversorgung für Peripheriegerät
+ \end{itemize}
+
+ \medskip
+
+ synchron
+ \begin{itemize}
+ \item
+ Abgleich über\\Taktleitung
+ \begin{picture}(0,0)
+ \put(0.4,-0.4){\includegraphics[width=9.7cm]{I2C_data_transfer.pdf}}
+ \end{picture}
+ \end{itemize}
+
+ \medskip
+
+ busfähig
+ \begin{itemize}
+ \item
+ \newterm{Master\/} initiiert Kommuniation und steuert Taktleitung
+ \item
+ erstes gesendetes Byte: \newterm{Adresse\/} des Teilnehmers
+ \item
+ 2 Adressen pro Teilnehmer: Lesen/Schreiben
+ \end{itemize}
+ \vspace*{-1cm}
+\end{frame}
+
+\subsection{SPI}
+
+\begin{frame}
+ \showsection
+ \showsubsection
+
+ Serial Peripheral Interface
+
+ \medskip
+
+ seriell
+ \begin{itemize}
+ \item
+ \newterm{MOSI\/}: Master Out, Slave In
+ \item
+ \newterm{MISO\/}: Master In, Slave Out
+ \item
+ \newterm{SCLK\/}: Taktleitung (Clock)
+ \item
+ \newterm{$\overline{\text{SS}}$\/}: Slave Select (invertiert)
+ \item
+ \newterm{GND\/}: gemeinsame Masse
+ \item
+ evtl.\ \newterm{VCC\/}: Stromversorgung für Peripheriegerät
+ \end{itemize}
+
+ \medskip
+
+ synchron
+ \begin{itemize}
+ \item
+ Abgleich über Taktleitung
+ \end{itemize}
+
+ \medskip
+
+ busfähig
+ \begin{itemize}
+ \item
+ \newterm{Master\/} initiiert Kommuniation und steuert Taktleitung
+ \item
+ \newterm{Slave\/} wird über \newterm{Slave Select\/} ausgewählt
+ \begin{picture}(0,0)
+ \only<1>{\put(-2.175,2.875){\includegraphics[scale=0.7]{SPI_single_slave.pdf}}}
+ \only<2>{\put(-2.0,3.0){\includegraphics[scale=0.7]{SPI_three_slaves.pdf}}}
+ \only<2>{\put(2.55,3.1){\begin{minipage}[t]{2.5cm}
+ \newterm{Stern}
+ \end{minipage}}}
+ \only<3->{\put(-2.0,3.0){\includegraphics[scale=0.7]{SPI_three_slaves_daisy_chained.pdf}}}
+ \only<3->{\put(2.55,3.1){\begin{minipage}[t]{2.5cm}
+ \newterm{Kaskade}\\
+ \newterm{Daisy Chain}\pause[4]\par\smallskip
+ \setlength{\leftskip}{-3.5cm}\small
+ Slave gibt MOSI-Input um 1 Takt verzögert
+ an MISO aus \textarrow\ Master setzt
+ "`im richtigen Moment"' $\overline{\text{SS}}$
+ \end{minipage}}}
+ \end{picture}
+ \end{itemize}
+ \vspace*{-1cm}
+
+\end{frame}
+
+
+\subsection{Beispiel: Benutzung des \protect\ItwoC-Busses}
+
+\begin{frame}[fragile]
+
+ \showsection
+ \showsubsection
+
+ \begin{picture}(0,0)
+ \put(8.75,-0.75){\includegraphics[height=2.75cm]{kompassmodul.jpg}}
+ \end{picture}%
+
+ \begin{onlyenv}<1>
+ \begin{lstlisting}[gobble=6]
+ void read_compass (uint16_t *x, uint16_t *y)
+ {
+ I2CTWI_transmit2Bytes (0x60, 0x00, 0x02); // set coil
+ mSleep (1);
+ I2CTWI_transmit2Bytes (0x60, 0x00, 0x04); // reset coil
+ mSleep (5);
+ uint8_t result[5];
+ I2CTWI_transmit2Bytes (0x60, 0x00, 0x01); // Messung starten
+ mSleep (5); // 5ms warten, bis Sensor fertig gemessen hat
+ I2CTWI_transmitByte (0x60, 0x01); // Leseindex setzen
+ I2CTWI_readBytes (0x61, result, 4); // lesen: msb x, lsb x, msb y, lsb y
+ result[0] &= 0b00001111; // Unwichtge Bits vom msb abschneiden
+ result[2] &= 0b00001111;
+ *x = (result[0] << 8) + result[1]; // Wert berechnen aus msb und lsb
+ *y = (result[2] << 8) + result[3];
+ }
+ \end{lstlisting}
+ \end{onlyenv}
+ \begin{onlyenv}<2-3>
+ \begin{lstlisting}[gobble=6,style=shy]
+ ²void read_compass (uint16_t *x, uint16_t *y)
+ { ... }
+
+ int main (void)
+ {
+ uint16_t compass_x, compass_y;
+ read_compass (&compass_x, &compass_y);¿
+ ³writeInteger (compass_x, DEC);
+ writeChar (' ');
+ writeInteger (compass_y, DEC);
+ writeChar ('\n');¿
+ ²return 0;
+ }¿
+ \end{lstlisting}
+ \end{onlyenv}
+ \begin{onlyenv}<4->
+ \begin{lstlisting}[gobble=6,style=shy]
+ °void read_compass (uint16_t *x, uint16_t *y)
+ {
+ I2CTWI_transmit2Bytes (0x60, 0x00, 0x02); // set coil
+ ¿mSleep (1);
+ I2CTWI_transmit2Bytes (0x60, 0x00, 0x04); // reset coil
+ mSleep (5);
+ uint8_t result[5];
+ I2CTWI_transmit2Bytes (0x60, 0x00, 0x01); // Messung starten
+ mSleep (5); // 5ms warten, bis Sensor fertig gemessen hat
+ I2CTWI_transmitByte (0x60, 0x01); // Leseindex setzen
+ I2CTWI_readBytes (0x61, result, 4); // lesen: msb x, lsb x, msb y, lsb y
+ result[0] &= 0b00001111; // Unwichtge Bits vom msb abschneiden
+ result[2] &= 0b00001111;
+ *x = (result[0] << 8) + result[1]; // Wert berechnen aus msb und lsb
+ *y = (result[2] << 8) + result[3];
+ °}¿
+ \end{lstlisting}
+ \end{onlyenv}
+ \begin{onlyenv}<5-7>
+ \begin{picture}(0,0)
+ \color{red}
+ \put(3.85,5.3){\vector(1,1){0.5}}
+ \put(3.5,5.2){\makebox(0,0)[t]{\shortstack{Gerät adressieren:\\Schreib-Adresse}}}
+ \end{picture}
+ \end{onlyenv}
+ \begin{onlyenv}<6-7>
+ \begin{picture}(0,0)
+ \color{red}
+ \put(5.25,4.5){\vector(0,1){1.3}}
+ \put(5.25,4.4){\makebox(0,0)[t]{\shortstack{Register-Nr.\\innerhalb des Geräts}}}
+ \end{picture}
+ \end{onlyenv}
+ \begin{onlyenv}<7>
+ \begin{picture}(0,0)
+ \color{red}
+ \put(6.6,5.3){\vector(-1,1){0.5}}
+ \put(6.95,5.2){\makebox(0,0)[t]{Befehl: Spule an}}
+ \end{picture}
+ \end{onlyenv}
+ \vspace*{-2cm}
+
+\end{frame}
+
+\begin{frame}[fragile]
+
+ \showsection
+ \showsubsection
+
+ \begin{picture}(0,0)
+ \put(8.75,-0.75){\includegraphics[height=2.75cm]{kompassmodul.jpg}}
+ \end{picture}%
+
+ \begin{lstlisting}[style=shy]
+ ¡void read_compass (uint16_t *x, uint16_t *y)
+ {
+ I2CTWI_transmit2Bytes (0x60, 0x00, 0x02); // set coil
+ mSleep (1);
+ I2CTWI_transmit2Bytes (0x60, 0x00, 0x04); // reset coil
+ mSleep (5);
+ ¿²uint8_t result[5];
+ I2CTWI_transmit2Bytes (0x60, 0x00, 0x01); // Messung starten
+ mSleep (5); // 5ms warten, bis Sensor fertig gemessen hat
+ ¿³I2CTWI_transmitByte (0x60, 0x01); // Leseindex setzen
+ ¿°I2CTWI_readBytes (0x61, result, 4); // lesen: msb x, lsb x, msb y, lsb y
+ result[0] &= 0b00001111; // Unwichtge Bits vom msb abschneiden
+ result[2] &= 0b00001111;
+ *x = (result[0] << 8) + result[1]; // Wert berechnen aus msb und lsb
+ *y = (result[2] << 8) + result[3];
+ ¿¡}¿
+ \end{lstlisting}
+ \vspace*{-2cm}
+
+\end{frame}
+
+\begin{frame}[fragile]
+
+ \showsection
+ \showsubsection
+
+ \begin{picture}(0,0)
+ \put(8.75,-0.75){\includegraphics[height=2.75cm]{kompassmodul.jpg}}
+ \end{picture}%
+ Messung:\\
+ Roboter im Kreis drehen lassen,\\
+ x- und y-Werte aufzeichnen\\
+ und gegeneinander auftragen
+
+ \smallskip
+ Ergebnis: Ellipse
+ \begin{picture}(0,0)(0,0.5)
+ \put(5,-3){\includegraphics[height=4cm]{kompass-messung.png}}
+ \end{picture}%
+
+ \bigskip
+ Anwendung:\\
+ Roboter in eine Himmelsrichtung ausrichten
+ \begin{itemize}
+ \item
+ Achsen normieren:\\
+ Mittelwert subtrahieren
+ \begin{picture}(0,0)(0,0.5)
+ \put(3.75,0.95){\vector(1,0){4}}
+ \put(7.55,0.90){\makebox(0,0)[t]{x}}
+ \put(5.75,-1.05){\vector(0,1){4}}
+ \put(5.75,2.95){\makebox(0,0)[r]{y}}
+ \end{picture}%
+ \item
+ Nulldurchgang einer Achse\\
+ markiert eine Himmelsrichtung
+ \item
+ Vorzeichen der anderen Achse\\
+ sagt aus, welche Himmelsrichtung
+ \end{itemize}
+ \vspace{-0.5cm}
+ \begin{flushright}
+ Beispiel: nach Norden ausrichten\\
+ Grob drehen, bis $y$ positiv ist,
+ fein drehen, bis $x = 0$ ist
+ \end{flushright}
+% $x = 0$, $y$ positiv: Norden\\
+% $x = 0$, $y$ negativ: Süden
+% $y = 0$, $x < 0$: Westen
+% $y = 0$, $x > 0$: Osten
+ \vspace*{-2cm}
+
+\end{frame}
+
+\nosectionnonumber{Vertiefung Systemtechnik -- Eingebettete Systeme}
+
+\begin{frame}
+
+ \shownosectionnonumber
+
+ \begin{itemize}
+ \item[\textbf{1}] \textbf{Einführung}
+ \hfill\makebox(0,0)[br]{\raisebox{2.25ex}{\url{https://gitlab.cvh-server.de/pgerwinski/es.git}}}%
+ \item[\textbf{2}] \textbf{Einführung in Unix}
+ \item[\textbf{3}] \textbf{TCP/IP in der Praxis}
+ \item[\textbf{4}] \textbf{Bus-Systeme}
+ \begin{itemize}
+ \color{medgreen}
+ \item[5.1] Was sind Bus-Systeme?
+ \item[5.2] RS-232
+ \item[5.3] \ItwoC\ (TWI)
+ \item[5.4] SPI
+ \item[5.5] Beispiel: Benutzung des \ItwoC-Busses
+ \end{itemize}
+ \item[\textbf{6}] \textbf{Echtzeit}
+ \begin{itemize}
+ \color{medgreen}
+ \item[5.1] Was ist Echtzeit?
+ \item[5.2] Echtzeitprogrammierung
+ \color{orange}
+ \item[5.3] Multitasking
+ \color{red}
+ \item[5.4] Ressourcen
+ \item[5.5] Prioritäten
+ \end{itemize}
+ \vspace*{-\smallskipamount}
+ \item[\textbf{\dots}]
+ \underconstruction
+ \end{itemize}
+
+\end{frame}
+
+\section{Echtzeit}
+
+\subsection{Was ist Echtzeit?}
+
+\begin{frame}
+
+ \showsection
+ \showsubsection
+
+ \begin{itemize}
+ \pause
+ \item
+ Animation in Echtzeit:\\
+ schnelle Berechnung anstatt Wiedergabe einer Aufzeichnung
+ \pause
+ \medskip
+ \item
+ Fantasy-Rollenspiel in Echtzeit:\\
+ Der Zeitverlauf der Spielwelt entspricht dem der realen Welt.
+ \pause
+ \medskip
+ \item
+ Datenverarbeitung in Echtzeit:\\
+ Die Daten werden so schnell verarbeitet, wie sie anfallen.
+ \pause
+ \medskip
+ \item
+ speziell: Echtzeit-Steuerung von Maschinen:\\
+ Die Berechnung kann mit den physikalischen Vorgängen schritthalten.
+ \pause
+ \bigskip
+ \arrowitem
+ "`Schnell genug."'
+ \end{itemize}
+
+\end{frame}
+
+\begin{frame}
+
+ \showsubsection
+
+ "`Schnell genug."' \pause-- "`Und wenn nicht?"'
+
+ \pause
+
+ \begin{itemize}
+ \item
+ "`Ganz schlecht."' \pause\textarrow\ \newterm{harte Echtzeit}
+ \begin{onlyenv}<4-8>
+ \begin{picture}(0,0)(0,-0.3)
+ \pause
+ \put(0,-4){\makebox(0,0)[br]{\includegraphics[height=3.5cm]{a380.jpg}}}
+ % http://de.wikipedia.org/w/index.php?title=Datei:Airbus_A380_overfly.jpg&filetimestamp=20111223141606
+ \pause
+ \put(0.2,-3.9){\makebox(0,0)[bl]{\includegraphics[height=4.0cm]{quadrocopter.jpg}}}
+ %\put(0.2,-3.5){\makebox(0,0)[bl]{\includegraphics[height=3.5cm]{mercedes-benz-w116.jpg}}}
+ % http://commons.wikimedia.org/wiki/File:1973-1980_Mercedes-Benz_450_SEL_%28W116%29_sedan_%282010-12-28%29_01.jpg
+ \pause
+ \put(-0.5,-4.2){\makebox(0,0)[tr]{\includegraphics[height=3.5cm]{herzschrittmacher.jpg}}}
+ % http://de.wikipedia.org/w/index.php?title=Datei:Pacemaker_GuidantMeridianSR.jpg&filetimestamp=20051203173642
+ \pause
+ \put(0,-4){\makebox(0,0)[tl]{\includegraphics[height=3.5cm]{curiosity.jpg}}}
+ % http://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1344
+ \end{picture}
+ \end{onlyenv}
+ \pause\\[2pt]
+ rechtzeitiges Ergebnis funktionsentscheidend
+
+ \smallskip
+
+ \pause
+ \item
+ "`Unschön."' \textarrow\ \newterm{weiche Echtzeit}
+ \begin{onlyenv}<10-12>
+ \begin{picture}(0,0)(0,0.3)
+ \pause
+ \put(0,-4){\makebox(0,0)[br]{\includegraphics[width=5cm]{Retribution_Engine_Screenshot_120807.jpg}}}
+ % http://en.wikipedia.org/wiki/File:Retribution_Engine_Screenshot_120807.jpg
+ \pause
+ \put(0.1,-4.5){\makebox(0,0)[bl]{\includegraphics[width=5cm]{Telefon_t-sinus-700.jpg}}}
+ % http://de.wikipedia.org/w/index.php?title=Datei:Telefon_t-sinus-700.jpg&filetimestamp=20050807203655
+ \end{picture}
+ \end{onlyenv}
+ \pause\\[2pt]
+ verspätetes Ergebnis qualitätsmindernd
+ \begin{itemize}
+ \baselineskip14pt\par
+ \item
+ verwenden und Verzögerung in Kauf nehmen
+ \item
+ verwerfen und Ausfall in Kauf nehmen
+ \end{itemize}
+
+ \smallskip
+
+ \pause
+ \item
+ "`Es gibt keinen festen Termin. Möglichst schnell halt."'\pause\\[2pt]
+ \textarrow\ \newterm{keine Echtzeit}
+ \end{itemize}
+
+\end{frame}
+
+\begin{frame}[fragile]
+
+ \showsubsection
+
+ Das Problem:
+ \vspace{-\bigskipamount}
+ \begin{center}
+ \begin{picture}(6,2)
+ \put(3,2){\makebox(0,0)[t]{Harte Echtzeitanforderungen}}
+ \put(3,0){\makebox(0,0)[b]{Ressourcen optimal nutzen}}
+% \put(2.75,0.875){\vector(1,3){0.25}}
+% \put(2.75,0.875){\line(2,1){0.5}}
+% \put(3.25,1.125){\vector(-1,-3){0.25}}
+ \put(2.70,0.350){\tikz{\draw[latex-latex](0.25,0.625)--(0,-0.12)--(0.5,0.12)--(0.25,-0.625);}}
+ \end{picture}
+% \begin{pdfpic}
+% \begin{pspicture}(6,2)
+% \put(3,2){\makebox(0,0)[t]{Harte Echtzeitanforderungen}}
+% \put(3,0){\makebox(0,0)[b]{Ressourcen optimal nutzen}}
+% \psline[arrows=<->](3,0.4)(3.2,1.125)(2.8,0.875)(3,1.6)
+% \end{pspicture}
+% \end{pdfpic}
+ \end{center}
+
+ \pause
+
+ Beispiel:
+ \begin{itemize}
+ \item
+ Eine Motorsteuerung benötigt alle \SI{2000}{\mics} einen Steuerimpuls,\\
+ dessen Berechnung maximal \SI{10}{\mics} dauert.
+ \pause[3]
+ \item
+ Entweder: Der Steuer-Computer macht noch andere Dinge.\\
+ \textarrow\ Risiko der Zeitüberschreitung
+ \pause
+ \item
+ Oder: Der Steuer-Computer macht nichts anderes.\\
+ \textarrow\ Verschwendung von Rechenzeit\\
+ \pause
+ {\color{red}\textarrow\ Na und?}
+ \end{itemize}
+
+\end{frame}
+
+\begin{frame}[fragile]
+
+ \showsubsection
+
+ Das Problem:
+ \vspace{-\bigskipamount}
+ \begin{center}
+ \begin{picture}(6,2)
+ \put(3,2){\makebox(0,0)[t]{Harte Echtzeitanforderungen}}
+ \put(3,0){\makebox(0,0)[b]{Ressourcen optimal nutzen}}
+% \put(2.75,0.875){\vector(1,3){0.25}}
+% \put(2.75,0.875){\line(2,1){0.5}}
+% \put(3.25,1.125){\vector(-1,-3){0.25}}
+ \put(2.70,0.350){\tikz{\draw[latex-latex](0.25,0.625)--(0,-0.12)--(0.5,0.12)--(0.25,-0.625);}}
+ \end{picture}
+% \begin{pdfpic}
+% \begin{pspicture}(6,2)
+% \put(3,2){\makebox(0,0)[t]{Harte Echtzeitanforderungen}}
+% \put(3,0){\makebox(0,0)[b]{Ressourcen optimal nutzen}}
+% \psline[arrows=<->](3,0.4)(3.2,1.125)(2.8,0.875)(3,1.6)
+% \end{pspicture}
+% \end{pdfpic}
+ \end{center}
+
+ \medskip
+
+ {\large\color{structure}\textbf{"`Verschwendung von Rechenzeit -- na und?"'}}
+
+ \medskip
+
+ \pause
+ Große Stückzahlen
+ \begin{itemize}
+ \item
+ 138\,000 Toyota Prius V von Mai 2011 bis April 2012
+ \end{itemize}
+
+ \medskip
+
+ \pause
+ Wertvolle Ressourcen
+ \begin{itemize}
+ \item
+ Fähigkeiten einer Raumsonde optimieren
+ % (Marsumlaufbahn: ab ca.~127\,000 Euro pro kg)
+ % 70000000 / 550000 = 127._27
+ % http://www.bernd-leitenberger.de/blog/2009/09/29/reduktion-der-kosten-von-planetenmissionen/
+ \only<.(1)>{\\[\medskipamount]\strut\hfill\makebox(0,0)[r]{\includegraphics[height=3.3cm]{curiosity.jpg}}\vspace*{-1cm}}
+ \pause
+ \item
+ Implantat: Platz- und Stromverbrauch minimieren
+ \only<.(1)>{\\\strut\hfill\makebox(0,0)[r]{\includegraphics[height=3.4cm]{herzschrittmacher.jpg}}\vspace*{-1cm}}
+ \end{itemize}
+
+ \bigskip
+
+ \pause
+ \textarrow\ {\large\color{structure}\textbf{Echtzeitprogrammierung}}\\[2pt]
+ \strut \phantom{\textarrow} Echtzeitanforderungen erfüllen, ohne Ressourcen zu verschwenden
+
+\end{frame}
+
+\subsection{Echtzeitprogrammierung}
+
+\begin{frame}
+
+ \showsubsection
+
+ Echtzeitanforderungen erfüllen, ohne Ressourcen zu verschwenden
+
+ \bigskip
+
+ \alt<.(1)>{Aber wie?}{Beispiele für Lösungen:}
+
+ \begin{itemize}
+ \pause
+ \item
+ ZigBee-Modul:\only<.(1)>{\hfill\makebox(0,0)[tr]{\includegraphics[width=5cm]{xbee.jpg}}}\\
+ % http://commons.wikimedia.org/wiki/File:Arduino_xbee.JPG
+ Funk- vs.\ UART-Protokoll\\
+ \textarrow\ dedizierte Hardware
+ \pause
+ \item
+ RP6:\\
+ Motorsteuerung vs.\ Anwender-Software\\
+ \textarrow\ spezielle Software
+ \only<.(1)>{\hfill\makebox(0,0)[r]{\includegraphics[width=5cm]{rp6.jpg}}}
+ \pause
+ \item
+ Quadrocopter:\\
+ Motorsteuerung vs.\ Sensoren-Abfrage\\
+ vs.\ Funk-Fernsteuerung \dots\\
+ \textarrow\ spezielle Software
+ \only<.(1)>{\hfill\makebox(0,0)[br]{\includegraphics[width=5cm]{quadrocopter.jpg}}}\\
+ \pause
+ \item
+ Flugzeugkabinensimulatortür:\\
+ Türsteuerung vs.\ Bedienung\\
+ \textarrow\ Echtzeitbetriebssystem
+ \only<.(1)>{\\[-3.2cm]\strut\hfill\makebox(0,0)[r]{\includegraphics[angle=-90,width=5cm]{dsc_8208.jpg}}}
+ \end{itemize}
+
+\end{frame}
+
+\begin{frame}
+
+ \showsubsection
+
+ Quadrocopter-Steuerung \emph{MultiWii}
+ \begin{itemize}
+ \item
+ Konfiguration durch bedingte Compilierung (Präprozessor)
+ \item
+ In der Hauptschleife wird 50mal pro Sekunde der RC-Task aufgerufen,\\
+ ansonsten zyklisch einer von bis zu 5 weiteren Tasks.
+ \end{itemize}
+
+ \pause
+
+ RP6-Steuerung
+ \begin{itemize}
+ \item
+ Konfiguration durch bedingte Compilierung (Präprozessor)
+ \item
+ Lichtschranken an Encoder-Scheiben lösen bei Bewegung Interrupts aus.\\
+ Die Interrupt-Handler zählen Variable hoch.
+ \item
+ 10000mal pro Sekunde: Timer-Interrupt\\
+ Durch Zähler im Interrupt-Handler: verschiedene Taktraten\\
+ 1000mal pro Sekunde: Stopwatches\\
+ 5mal pro Sekunde: Blinkende Power-On-LED\\
+ 1000mal pro Sekunde: Bumper, ACS, PWM zur Motorsteuerung\\
+ Geschwindigkeitsmessung durch Zählen der Ticks in 0.2\,s\\
+ Anpassung der Motorkraft in $\pm$1-Schritten
+ \pause
+ \item
+ Nebenbei: \only<4->{1 }Benutzerprogramm
+ \end{itemize}
+
+\end{frame}
+
+\subsection{Multitasking}
+
+\begin{frame}
+
+ \showsubsection
+
+ \begin{itemize}
+ \item
+ \newterm{Kooperatives Multitasking}\\
+ Prozesse geben freiwillig Rechenzeit ab
+ \item
+ \newterm{Präemptives Multitasking}\\
+ Das Betriebssystem unterbricht laufende Prozesse\\
+ (englisch: \emph{to pre-empt\/} -- jemandem zuvorkommen)
+ \bigskip
+ \item
+ \newterm{Scheduler}\\
+ Steuerprogramm, das Prozessen Rechenzeit zuteilt
+ \item
+ \newterm{Kontextwechsel}\\
+ Umschalten zwischen zwei Prozessen
+ \item
+ \newterm{Round-Robin-Verfahren (Rundlauf)}\\
+ Zuteilung von \newterm{Zeitschlitzen\/} auf einer \newterm{Zeitscheibe} an die Prozesse
+ \bigskip
+ \pause
+ \item
+ Ausblick: Zuteilung von Rechenzeit = wichtiger Spezialfall\\
+ allgemein: Zuteilung von Ressourcen
+ \end{itemize}
+
+\end{frame}
+
+\subsectionnonumber{Beispiele für Multitasking}
+
+\begin{frame}
+
+ \showsubsectionnonumber
+
+ Quadrocopter-Steuerung \emph{MultiWii}
+ \begin{itemize}
+ \item
+ Konfiguration durch bedingte Compilierung (Präprozessor)
+ \item
+ In der Hauptschleife wird 50mal pro Sekunde der RC-Task aufgerufen,\\
+ ansonsten zyklisch einer von bis zu 5 weiteren Tasks.
+ \end{itemize}
+
+ RP6-Steuerung
+ \begin{itemize}
+ \item
+ Konfiguration durch bedingte Compilierung (Präprozessor)
+ \item
+ Lichtschranken an Encoder-Scheiben lösen bei Bewegung Interrupts aus.\\
+ Die Interrupt-Handler zählen Variable hoch.
+ \item
+ 10000mal pro Sekunde: Timer-Interrupt\\
+ verschiedene Tasks werden unterschiedlich häufig aufgerufen
+ \item
+ Nebenbei: 1 Benutzerprogramm
+ \end{itemize}
+
+ Linux 0.01
+ \begin{itemize}
+ \item
+ Timer-Interrupt:\only<2->{ Zähler des aktuellen Tasks wird dekrementiert;}\\
+ Task mit höchstem Zähler bekommt Rechenzeit.
+ \item
+ Wenn es keinen laufbereiten Task mit positivem Zähler gibt,\\
+ bekommen alle Tasks gemäß ihrer Priorität neue Zähler zugewiesen.
+ \item
+ \emph{keine\/} harte Echtzeit
+ % Aufgabe: Wo wird der Zähler heruntergezählt?
+ \end{itemize}
+
+\end{frame}
+
+\subsectionnonumber{Zombies}
+
+\begin{frame}
+
+ \showsubsectionnonumber
+
+ \pause
+ Wikipedia:
+ \begin{quote}
+ Als Zombie wird die fiktive Figur eines zum Leben erweckten
+ Toten (Untoter) oder eines seiner Seele beraubten, willenlosen
+ Wesens bezeichnet. Der Begriff leitet sich von dem Wort nzùmbe
+ aus der zentralafrikanischen Sprache Kimbundu ab und bezeichnet
+ dort ursprünglich einen Totengeist.
+ \end{quote}
+
+ \bigskip
+
+ \pause
+ Ein Zombie-Prozeß ist bereits beendet ("`tot"'),\\
+ bekommt keine Rechenzeit mehr ("`seiner Seele beraubt"'),\\
+ hat alle belegten Ressourcen wieder freigegeben ("`willenlos"'),\\
+ wird aber noch in der Prozeßliste geführt ("`untot"').
+ \begin{itemize}
+ \pause
+ \item
+ Warum?
+ \textarrow\
+ Ein anderer Prozeß (Elternprozeß) wartet noch auf den
+ Rückgabewert des beendeten Prozesses.
+ \pause
+ \item
+ Schadet das?
+ \textarrow\
+ Nein.
+ \pause
+ \item
+ Aber?
+ \textarrow\
+ Wenn sich Zombie-Prozesse anhäufen, deutet dies auf einen
+ Prozeß hin, der andere Prozesse erzeugt und anschließend "`hängt"'.
+ \pause
+ \item
+ Beispiel:
+ Datenträger entfernt, zugreifender Prozeß "`hängt"'.\\
+ \textarrow\
+ Tochterprozesse werden zu Zombies.
+ \end{itemize}
+
+\end{frame}
+
+\subsectionnonumber{Multitasking}
+
+\begin{frame}
+
+ \showsection
+ \showsubsection
+
+ \begin{minipage}[t]{6cm}
+ Qualitätssicherung beim Multitasking
+ \begin{itemize}
+ \item<3->
+ Verschiedene Anforderungen:
+ \newterm{Latenz\/} vs.\ \newterm{Jitter\/}\\
+ vs.\ \newterm{Durchsatz}
+ \smallskip
+ \begin{onlyenv}<4>
+ \begin{itemize}
+ \item
+ \newterm{Latenz:} interaktive Anwendungen
+ \item
+ \newterm{Jitter:} Echtzeitanwendungen
+ \item
+ \newterm{Durchsatz:} Stapelverarbeitung
+ \end{itemize}
+ \vspace*{-3cm}
+ \end{onlyenv}
+ \item<5->
+ Ressourcen reservieren:\\
+ \newterm{Mutexe}
+ \only<6->{(= spezielle \newterm{Semaphore\/})\\}
+ \only<7->{\textarrow\ kommt gleich}
+ \item<8->
+ Verschiedene Methoden\\
+ der Priorisierung\\
+ \textarrow\ später\\
+ \strut
+ \item<9->
+ Umgehung der Probleme durch
+ speziell geschriebene Software\\
+ (MultiWii, RP6, \dots)
+ \end{itemize}
+ \end{minipage}
+ \hfill
+ \pause
+ \begin{minipage}[t]{6.2cm}
+ Qualitätssicherung für Netzwerke:
+ \begin{itemize}
+ \item
+ Verschiedene Anforderungen:
+ \newterm{Latenz\/} vs.\ \newterm{Jitter\/} vs.\ \newterm{Verluste\/}\\vs.\ \newterm{Durchsatz}
+ \item
+ Ressourcen reservieren:\\
+ \newterm{IntServ} mit \newterm{Resource Reservation Protocol (RSVP)}
+ \item
+ Klassifizierung und Priorisierung:
+ \newterm{DiffServ} mit Type-of-Service-Bits (IPv4)
+ bzw.\ Traffic-Class-Bits (IPv6) im IP-Header
+ \item
+ Eigenes Protokoll (Telefondienste):\\
+ \newterm{Asynchronous Transfer Mode (ATM)}
+ \end{itemize}
+ \end{minipage}
+
+\end{frame}
+
+\subsection{Ressourcen}
+
+\begin{frame}
+
+ \showsection
+ \showsubsection
+
+ Ressourcen reservieren
+ \begin{itemize}
+ \item
+ \newterm{Semaphor}\\
+ gemeinsame Variable mehrerer Prozesse\\
+ zur Regelung des Zugriffs auf eine Ressource\\[\smallskipamount]
+ Ressource belegt \textarrow\ Kontextwechsel
+ \begin{onlyenv}<1>
+ \par\medskip
+ griechisch: \emph{sema\/} -- Zeichen, \emph{pherein\/} -- tragen\\
+ "`Eisenbahnsignal"'
+ \vspace*{-3cm}
+ \end{onlyenv}
+ \pause
+ \medskip
+ \item
+ \newterm{Mutex}\\
+ Mechanismus, damit immer nur ein Prozeß gleichzeitig\\
+ auf eine Ressource zugreifen kann
+ \begin{onlyenv}<2>
+ \par\medskip
+ englisch: \emph{mutual exclusion\/} -- wechselseitiger Ausschluß\\
+ spezieller binärer Semaphor: nur "`Besitzer"' darf freigeben\\
+ % allgemein: auch jemand anderer dürfte freigeben
+ \vspace*{-3cm}
+ \end{onlyenv}
+ \pause
+ \medskip
+ \item
+ \newterm{Spinlock} (\emph{busy waiting\/})\\
+ leichtgewichtige Alternative zu Kontextwechsel
+ \begin{onlyenv}<3>
+ \par\medskip
+ englisch: \emph{spin\/} -- rotieren, \emph{lock\/} Sperre\\
+ \emph{busy waiting} auf etwas Schnelles, z.\,B.\ auf einen Semaphor\\[\medskipamount]
+ Hardware-Unterstützung:
+ Prüfen, ob Variable bestimmten Wert hat;\\
+ wenn ja, auf anderen Wert setzen; andere Prozessoren solange anhalten
+ \vspace*{-3cm}
+ \end{onlyenv}
+ \pause
+ \medskip
+ \item
+ \newterm{Kritischer Abschnitt -- critical section}\\
+ Programmabschnitt zwischen Reservierung\\
+ und Freigabe einer Ressource\\
+ \textarrow\ sollte immer so kurz wie möglich sein
+ \end{itemize}
+ \vspace*{-1cm}
+
+\end{frame}
+
+\begin{frame}
+
+ \showsection
+ \showsubsection
+
+ Ressourcen reservieren --
+ Beispiel: \file{linux-3.7rc1}
+ \begin{itemize}
+ \item
+ \newterm{Semaphor}\\
+ \file{kernel/semaphor.c}\\
+ \file{drivers/usb/core/file.c}
+ \medskip
+ \item
+ \newterm{Mutex}\\
+ \file{kernel/mutex.c}\\
+ \file{drivers/usb/serial/usb-serial.c}
+ \medskip
+ \item
+ \newterm{Spinlock}\\
+ \file{kernel/spinlock.c}\\
+ \file{kernel/semaphor.c},
+ \file{kernel/mutex.c}
+ \end{itemize}
+
+ % Aufgabe: Anwendungsarten im MultiWii- und RP6-Code identifizieren
+
+ % evtl. Aufgabe: Warte-Problem
+
+ % Aufgabe: Wie lösen bekannte Multitasking-Betriebssysteme
+ % das o.a. Zuteilungsproblem?
+
+ % Danach: Semaphoren, Mutexe, Spinlocks
+ % Priorisierungsmethoden und -probleme
+
+ % Festplatten: completely fair queueing
+ % cat /sys/block/sdc/queue/scheduler
+ % "noop" hat sich für SVG gelohnt
+
+ % Virtualisierung + Kernel-Threads + Multiprozessorsystem = Chaos
+
+\end{frame}
+
+\begin{frame}[fragile]
+
+ \textbf{Beispiel:}
+ \lstinline{usb_serial_get_by_index()} -- serielle Schnittstelle reservieren
+
+ Datei \file{linux-3.7-rc1/drivers/usb/serial/usb-serial.c}, ab Zeile 62
+
+ \medskip
+
+ \begin{lstlisting}
+ struct usb_serial *usb_serial_get_by_index (unsigned index)
+ {
+ struct usb_serial *serial;
+ mutex_lock (&table_lock);
+ serial = serial_table[index];
+ if (serial)
+ {
+ mutex_lock (&serial->disc_mutex);
+ if (serial->disconnected)
+ {
+ mutex_unlock (&serial->disc_mutex);
+ serial = NULL;
+ }
+ else
+ kref_get (&serial->kref);
+ }
+ mutex_unlock (&table_lock);
+ return serial;
+ }
+ \end{lstlisting}
+ \begin{picture}(0,0)
+ \color{red}
+ \put(5.1,6.85){\vector(-1,0){0.5}}
+ \put(5.2,6.85){\makebox(0,0)[l]{exklusiven Zugriff auf Tabelle sichern}}
+ \put(5.4,1.35){\vector(-1,0){0.5}}
+ \put(5.5,1.35){\makebox(0,0)[l]{\shortstack[l]{exklusiven Zugriff auf Tabelle\\wieder freigeben}}}
+ \end{picture}
+
+\end{frame}
+
+\setlength{\pdfpageheight}{48cm}
+
+\begin{frame}[fragile]
+
+ \lstinline{mutex_lock()} -- Ressource beanspruchen, notfalls warten
+
+ Datei \file{linux-3.7-rc1/drivers/usb/serial/usb-serial.c}, ab Zeile 62
+
+ \medskip
+
+ \begin{lstlisting}
+ void __sched mutex_lock (struct mutex *lock)
+ {
+ might_sleep ();
+ __mutex_fastpath_lock (&lock->count, __mutex_lock_slowpath);
+ mutex_set_owner (lock);
+ }
+ \end{lstlisting}
+ \begin{picture}(0,0)
+ \color{red}
+ \put(11.6,1.35){\line(-1,0){1}}
+ \put(11.6,1.35){\line(0,-1){2.45}}
+ \put(11.6,-1.10){\vector(-1,0){2.0}}
+ \end{picture}
+
+ \bigskip
+
+ Datei \file{linux-3.7-rc1/arch/x86/include/asm/mutex\_32.h}, ab Zeile 24
+
+ Macro-Definition für \lstinline{__mutex_fastpath_lock} (expandiert)
+
+ \medskip
+
+ Assembler:
+ \begin{lstlisting}[language={[x86masm]Assembler}]
+ lock dec (lock->count)
+ jns 1
+ call __mutex_lock_slowpath
+ 1:
+ \end{lstlisting}
+ \begin{picture}(0,0)
+ \color{red}
+ \put(9,0.95){\line(-1,0){3.5}}
+ \put(9,0.95){\line(0,-1){2.5}}
+ \put(9.0,-1.55){\vector(-1,0){1.0}}
+ \end{picture}
+
+ \bigskip
+
+ Datei \file{linux-3.7-rc1/kernel/mutex.c}, ab Zeile 398
+
+ \medskip
+
+ \begin{lstlisting}
+ static __used noinline void __sched
+ __mutex_lock_slowpath (atomic_t *lock_count)
+ {
+ struct mutex *lock = container_of (lock_count, struct mutex, count);
+ __mutex_lock_common (lock, TASK_UNINTERRUPTIBLE, 0,
+ NULL, _RET_IP_);
+ }
+ \end{lstlisting}
+ \begin{picture}(0,0)
+ \color{red}
+ \put(11.0,1.40){\line(-1,0){1.0}}
+ \put(11.0,1.40){\vector(0,-1){2.5}}
+ \end{picture}
+
+ \bigskip
+
+ Datei \file{linux-3.7-rc1/kernel/mutex.c}, ab Zeile 132
+
+ \medskip
+
+ \begin{lstlisting}
+ static inline int __sched
+ __mutex_lock_common (struct mutex *lock, long state, unsigned int subclass,
+ struct lockdep_map *nest_lock, unsigned long ip)
+ {
+ struct task_struct *task = current;
+ struct mutex_waiter waiter;
+ unsigned long flags;
+
+ preempt_disable ();
+ mutex_acquire_nest (&lock->dep_map, subclass, 0, nest_lock, ip);
+
+ /* ... */
+
+ spin_lock_mutex (&lock->wait_lock, flags);
+
+ debug_mutex_lock_common (lock, &waiter);
+ debug_mutex_add_waiter (lock, &waiter, task_thread_info (task));
+
+ /* add waiting tasks to the end of the waitqueue (FIFO): */
+ list_add_tail (&waiter.list, &lock->wait_list);
+ waiter.task = task;
+
+ if (atomic_xchg (&lock->count, -1) == 1)
+ goto done;
+
+ lock_contended (&lock->dep_map, ip);
+
+ for (;;)
+ {
+ /*
+ * Lets try to take the lock again - this is needed even if
+ * we get here for the first time (shortly after failing to
+ * acquire the lock), to make sure that we get a wakeup once
+ * it's unlocked. Later on, if we sleep, this is the
+ * operation that gives us the lock. We xchg it to -1, so
+ * that when we release the lock, we properly wake up the
+ * other waiters:
+ */
+ if (atomic_xchg (&lock->count, -1) == 1)
+ break;
+
+ /*
+ * got a signal? (This code gets eliminated in the
+ * TASK_UNINTERRUPTIBLE case.)
+ */
+ if (unlikely (signal_pending_state (state, task)))
+ {
+ mutex_remove_waiter (lock, &waiter, task_thread_info (task));
+ mutex_release (&lock->dep_map, 1, ip);
+ spin_unlock_mutex (&lock->wait_lock, flags);
+
+ debug_mutex_free_waiter (&waiter);
+ preempt_enable ();
+ return -EINTR;
+ }
+ __set_task_state (task, state);
+
+ /* didn't get the lock, go to sleep: */
+ spin_unlock_mutex (&lock->wait_lock, flags);
+ schedule_preempt_disabled ();
+ spin_lock_mutex (&lock->wait_lock, flags);
+ }
+
+ done:
+ lock_acquired (&lock->dep_map, ip);
+ /* got the lock - rejoice! */
+ mutex_remove_waiter (lock, &waiter, current_thread_info ());
+ mutex_set_owner (lock);
+
+ /* set it to 0 if there are no waiters left: */
+ if (likely (list_empty (&lock->wait_list)))
+ atomic_set (&lock->count, 0);
+
+ spin_unlock_mutex (&lock->wait_lock, flags);
+
+ debug_mutex_free_waiter (&waiter);
+ preempt_enable ();
+
+ return 0;
+ }
+ \end{lstlisting}
+ \begin{picture}(0,0)
+ \color{red}
+ \put(7.9,28.3){\vector(-1,0){0.5}}
+ \put(8.0,28.3){\makebox(0,0)[l]{\shortstack[l]{exklusiven Zugriff\\auf Mutex sichern}}}
+ \put(7.4,2.3){\vector(-1,1){0.4}}
+ \put(7.5,2.0){\makebox(0,0)[l]{\shortstack[l]{exklusiven Zugriff auf Mutex\\wieder freigeben}}}
+ \end{picture}
+
+\end{frame}
+
+\setlength{\pdfpageheight}{40.5cm}
+
+\begin{frame}[fragile]
+
+ \lstinline{spin_lock_mutex()} -- Mutex beanspruchen, notfalls \emph{busy waiting}
+
+ Datei \file{linux-3.7-rc1/kernel/mutex.h}, ab Zeile 12
+
+ \medskip
+
+ \begin{lstlisting}
+ #define spin_lock_mutex(lock, flags) \
+ do \
+ { \
+ spin_lock (lock); \
+ (void) (flags); \
+ } \
+ while (0)
+ \end{lstlisting}
+ \begin{picture}(0,0)
+ \color{red}
+ \put(8.5,1.75){\line(-1,0){4.5}}
+ \put(8.5,1.75){\line(0,-1){2.9}}
+ \put(8.5,-1.15){\vector(-1,0){1.0}}
+ \end{picture}
+
+ \bigskip
+
+ Datei \file{linux-3.7-rc1/kernel/spinlock.h}, ab Zeile 283
+
+ \medskip
+
+ \begin{lstlisting}
+ static inline void spin_lock (spinlock_t *lock)
+ {
+ raw_spin_lock (&lock->rlock);
+ }
+ \end{lstlisting}
+ \begin{picture}(0,0)
+ \color{red}
+ \put(9.3,0.95){\line(-1,0){4.0}}
+ \put(9.3,0.95){\line(0,-1){2.1}}
+ \put(9.3,-1.15){\vector(-1,0){1.0}}
+ \end{picture}
+
+ \bigskip
+
+ Datei \file{linux-3.7-rc1/kernel/spinlock.h}, Zeile 170
+
+ \medskip
+
+ \begin{lstlisting}
+ #define raw_spin_lock(lock) _raw_spin_lock (lock)
+ \end{lstlisting}
+ \begin{picture}(0,0)
+ \color{red}
+ \put(10.0,0.55){\line(-1,0){0.5}}
+ \put(10.0,0.55){\line(0,-1){1.7}}
+ \put(10.0,-1.15){\vector(-1,0){1.3}}
+ \end{picture}
+
+ \bigskip
+
+ Datei \file{linux-3.7-rc1/include/linux/spinlock\_api\_smp.h}, Zeile 47
+
+ \medskip
+
+ \begin{lstlisting}
+ #define _raw_spin_lock(lock) __raw_spin_lock (lock)
+ \end{lstlisting}
+ \begin{picture}(0,0)
+ \color{red}
+ \put(10.7,0.55){\line(-1,0){0.5}}
+ \put(10.7,0.55){\line(0,-1){1.75}}
+ \put(10.7,-1.2){\vector(-1,0){2.3}}
+ \end{picture}
+
+ \bigskip
+
+ Datei \file{linux-3.7-rc1/kernel/spinlock.c}, ab Zeile 46 (expandiert):
+
+ \medskip
+
+ \begin{lstlisting}
+ void __lockfunc __raw_spin_lock (spinlock_t *lock)
+ {
+ for (;;)
+ {
+ preempt_disable ();
+ if (likely (do_raw_spin_trylock (lock)))
+ break;
+ preempt_enable ();
+
+ if (!(lock)->break_lock)
+ (lock)->break_lock = 1;
+ while (!raw_spin_can_lock (lock) && (lock)->break_lock)
+ arch_spin_relax (&lock->raw_lock);
+ }
+ (lock)->break_lock = 0;
+ }
+ \end{lstlisting}
+ \begin{picture}(0,0)
+ \color{red}
+ \put(10.7,4.75){\line(-1,0){3.5}}
+ \put(10.7,4.75){\line(0,-1){5.95}}
+ \put(10.7,-1.2){\vector(-1,0){1.1}}
+ \end{picture}
+
+ \bigskip
+
+ Datei \file{linux-3.7-rc1/include/linux/spinlock.h}, ab Zeile 150:
+
+ \medskip
+
+ \begin{lstlisting}
+ static inline int do_raw_spin_trylock (raw_spinlock_t *lock)
+ {
+ return arch_spin_trylock (&(lock)->raw_lock);
+ }
+ \end{lstlisting}
+ \begin{picture}(0,0)
+ \color{red}
+ \put(11.5,0.95){\line(-1,0){3.5}}
+ \put(11.5,0.95){\line(0,-1){2.1}}
+ \put(11.5,-1.15){\vector(-1,0){0.7}}
+ \end{picture}
+
+ \bigskip
+
+ Datei \file{arch/x86/include/asm/spinlock.h}, ab Zeile 116:
+
+ \medskip
+
+ \begin{lstlisting}
+ static __always_inline int arch_spin_trylock (arch_spinlock_t *lock)
+ {
+ return __ticket_spin_trylock (lock);
+ }
+ \end{lstlisting}
+ \begin{picture}(0,0)
+ \color{red}
+ \put(9.5,0.95){\line(-1,0){3.5}}
+ \put(9.5,0.95){\vector(0,-1){1.7}}
+ \end{picture}
+
+ \bigskip
+
+ Datei \file{arch/x86/include/asm/spinlock.h}, ab Zeile 65:
+
+ \medskip
+
+ \begin{lstlisting}
+ static __always_inline int __ticket_spin_trylock (arch_spinlock_t *lock)
+ {
+ arch_spinlock_t old, new;
+
+ old.tickets = ACCESS_ONCE (lock->tickets);
+ if (old.tickets.head != old.tickets.tail)
+ return 0;
+
+ new.head_tail = old.head_tail + (1 << TICKET_SHIFT);
+
+ /* cmpxchg is a full barrier, so nothing can move before it */
+ return cmpxchg (&lock->head_tail, old.head_tail, new.head_tail) == old.head_tail;
+ }
+ \end{lstlisting}
+ \begin{picture}(0,0)
+ \color{red}
+ \put(2.2,0.3){\line(0,1){0.4}}
+ \put(9.0,0.3){\line(-1,0){6.8}}
+ \put(9.0,0.3){\line(0,-1){1.45}}
+ \put(9.0,-1.15){\vector(-1,0){3.2}}
+ \end{picture}
+
+ \bigskip
+
+ Datei \file{arch/x86/include/asm/cmpxchg.h}, ab Zeile 147:
+
+ \medskip
+
+ \begin{lstlisting}
+ #define cmpxchg(ptr, old, new) \
+ __cmpxchg (ptr, old, new, sizeof (*(ptr)))
+ \end{lstlisting}
+ \begin{picture}(0,0)
+ \color{red}
+ \put(9.0,0.5){\line(-1,0){1.8}}
+ \put(9.0,0.5){\line(0,-1){1.65}}
+ \put(9.0,-1.15){\vector(-1,0){2.2}}
+ \end{picture}
+
+ \bigskip
+
+ Datei \file{arch/x86/include/asm/cmpxchg.h}, ab Zeile 131:
+
+ \medskip
+
+ \begin{lstlisting}
+ #define __cmpxchg(ptr, old, new, size) \
+ __raw_cmpxchg ((ptr), (old), (new), (size), LOCK_PREFIX)
+ \end{lstlisting}
+ \begin{picture}(0,0)
+ \color{red}
+ \put(2.2,-0.1){\line(0,1){0.3}}
+ \put(9.0,-0.1){\line(-1,0){6.8}}
+ \put(9.0,-0.1){\line(0,-1){1.05}}
+ \put(9.0,-1.15){\vector(-1,0){2.2}}
+ \end{picture}
+
+ \bigskip
+
+ Datei \file{arch/x86/include/asm/cmpxchg.h}, ab Zeile 110:
+
+ \medskip
+
+ \begin{lstlisting}
+ asm volatile (lock "cmpxchgl %2,%1" \
+ : "=a" (__ret), "+m" (*__ptr) \
+ : "r" (__new), "0" (__old) \
+ : "memory");
+ \end{lstlisting}
+ \begin{picture}(0,0)
+ \color{red}
+ \put(9.8,1.8){\vector(-1,0){0.6}}
+ \put(9.8,1.2){\line(0,1){0.6}}
+ \put(9.8,1.1){\makebox(0,0)[t]{\shortstack{atomarer und exklusiver\\Zugriff auf Spinlock\\durch Hardware-Unterstützung}}}
+ \end{picture}
+
+\end{frame}
+
+\setlength{\pdfpageheight}{\normalpdfpageheight}
+
+%\sectionnonumber{Literaturempfehlung}
+%\subsectionnonumber{Automotive Embedded Systeme}
+%
+%\begin{frame}[c]
+%
+% \showsectionnonumber
+%
+% Prof.\ Dr.\ Joachim Wietzke, FH Darmstadt,\\
+% Prof.\ Dr.\ Manh Tien Tran, FH Kaiserslautern:
+%
+% \medskip
+%
+% \showsubsectionnonumber
+%
+% \vspace{-\medskipamount}
+%
+% Springer-Verlag, Berlin, Heidelberg 2005
+%
+% \bigskip
+%
+% Lizenz: proprietär
+%
+% \medskip
+%
+% (gesetzt mit \textrm{\LaTeX}, ca.\ \EUR{10})
+%
+%\end{frame}
+
+\begin{frame}
+
+ \showsection
+ \showsubsection
+
+ Ressourcen reservieren
+ \begin{itemize}
+ \item
+ \newterm{Semaphor}\\
+ gemeinsame Variable mehrerer Prozesse\\
+ zur Regelung des Zugriffs auf eine Ressource\\[\smallskipamount]
+ Ressource belegt \textarrow\ Kontextwechsel
+ \medskip
+ \item
+ \newterm{Mutex}\\
+ Mechanismus, damit immer nur ein Prozeß gleichzeitig\\
+ auf eine Ressource zugreifen kann
+ \medskip
+ \item
+ \newterm{Spinlock} (\emph{busy waiting\/})\\
+ leichtgewichtige Alternative zu Kontextwechsel
+ \medskip
+ \item
+ \newterm{Kritischer Abschnitt -- critical section}\\
+ Programmabschnitt zwischen Reservierung\\
+ und Freigabe einer Ressource\\
+ \textarrow\ sollte immer so kurz wie möglich sein
+ \end{itemize}
+ \vspace*{-1cm}
+
+\end{frame}
+
+\begin{frame}
+
+ \showsection
+ \showsubsection
+
+ \begin{picture}(0,0)
+ \only<2-3>{\put(6.3,-7){\includegraphics[height=6cm]{philosophenproblem.jpg}}}
+ \end{picture}%
+ \newterm{Verklemmungen\/}: Gegenseitiges Blockieren von Ressourcen
+ \begin{itemize}
+ \item
+ \newterm{Deadlock\/}: Prozeß wartet
+ \item
+ \newterm{Livelock\/}: Prozeß macht andere Dinge\\
+ (z.\,B.\ \emph{busy waiting\/})
+ \end{itemize}
+
+ \pause
+ \bigskip
+
+ Beispiel: Philosophenproblem
+
+ \only<2-3>{%
+ \begin{itemize}
+ \item
+ 5 Philosophen, 5 Gabeln
+ \item
+ 2 Gabeln zum Essen notwendig
+ \item
+ Wer essen will, nimmt eine Gabel\\
+ und wartet notfalls auf die zweite.
+ \item
+ Keiner legt eine einzelne Gabel\\
+ wieder zurück.
+ \end{itemize}
+ Jeder hält 1 Gabel \textarrow\ \newterm{Verklemmung}\\[0.5\smallskipamount]
+ \pause
+ \strut\quad schweigen \textarrow\ \newterm{Deadlock}\\
+ \strut\quad philosophieren weiter \textarrow\ \newterm{Livelock}\\[-1cm]
+ }
+ \only<4->{%
+ \bigskip
+
+ Bedingungen für Verklemmungen:
+
+ \begin{minipage}[t]{4.5cm}
+ \begin{itemize}
+ \item
+ Exklusivität
+ \item
+ \newterm{hold and wait}
+ \item
+ Entzug nicht möglich
+ \item
+ zirkuläre Blockade
+ \end{itemize}
+ \end{minipage}\pause[5]
+ \begin{minipage}[t]{7.5cm}
+ \begin{itemize}
+ \arrowitem
+ Spooling
+ \arrowitem
+ simultane Zuteilung
+ \arrowitem
+ Prozesse suspendieren, beenden, \newterm{Rollback}
+ \arrowitem
+ Reihenfolge abhängig von Ressourcen
+ \end{itemize}
+ \end{minipage}
+ }
+
+\end{frame}
+
+\subsection{Prioritäten}
+
+\begin{frame}
+
+ \showsection
+ \showsubsection
+
+ Linux 0.01
+ \begin{itemize}
+ \item
+ Timer-Interrupt: Zähler des aktuellen Prozesses wird dekrementiert;\\
+ Prozeß mit höchstem Zähler bekommt Rechenzeit.
+ \item
+ Wenn es keinen laufbereiten Prozeß mit positivem Zähler gibt,\\
+ bekommen alle Prozesse gemäß ihrer \newterm{Priorität\/} neue Zähler zugewiesen.
+ \item
+ \emph{keine\/} harte Echtzeit
+ \arrowitem
+ \newterm{dynamische Prioritätenvergabe\/}:\\
+ Rechenzeit hängt vom Verhalten des Prozesses ab
+ \end{itemize}
+
+ \medskip
+
+ Echtzeitbetriebssysteme
+ \begin{itemize}
+ \item
+ Prozesse können einen festen Anteil an Rechenzeit bekommen.
+ \item
+ Bei Ereignissen können Prozesse hoher Priorität\\
+ Prozesse niedriger Priorität unterbrechen, aber nicht umgekehrt.
+ \arrowitem
+ \newterm{statische Prioritätenvergabe}
+ \end{itemize}
+
+\end{frame}
+
+\begin{frame}
+
+ \showsection
+ \showsubsection
+
+ Echtzeitbetriebssysteme
+ \begin{itemize}
+ \item
+ Prozesse können einen festen Anteil an Rechenzeit bekommen.
+ \item
+ Bei Ereignissen können Prozesse hoher Priorität\\
+ Prozesse niedriger Priorität unterbrechen, aber nicht umgekehrt.
+ \end{itemize}
+
+ \vspace{0cm plus 1filll}
+
+ \begin{center}
+ \begin{picture}(11,4)(-1,0)
+ \small
+
+ \put(-0.1,0.5){\vector(1,0){10.1}}
+ \put(9.75,0.4){\makebox(0,0)[tr]{Zeit}}
+ \put(0,0.4){\vector(0,1){3.6}}
+ \put(-0.1,3.75){\makebox(0,0)[tr]{Priorität}}
+
+ \put(1,3){{\color{lightorange}\rule{0.5cm}{0.4cm}}}
+ \put(3,3){{\color{lightorange}\rule{0.7cm}{0.4cm}}}
+ \put(5,3){{\color{lightorange}\rule{0.6cm}{0.4cm}}}
+ \put(7,3){{\color{lightorange}\rule{0.5cm}{0.4cm}}}
+ \put(9,3){{\color{lightorange}\rule{0.7cm}{0.4cm}}}
+ \put(0,3){\line(1,0){10}}
+
+ \put(0,1){{\color{lightgreen}\rule{1cm}{0.4cm}}}
+ \put(1.5,1){{\color{lightgreen}\rule{1.5cm}{0.4cm}}}
+ \put(3.7,1){{\color{lightgreen}\rule{0.6cm}{0.4cm}}}
+ \alt<1>{%
+ \put(7.9,1){{\color{lightgreen}\rule{1.1cm}{0.4cm}}}
+ }{%
+ \put(8.1,1){{\color{lightgreen}\rule{0.9cm}{0.4cm}}}
+ }
+ \put(9.7,1){{\color{lightgreen}\rule{0.3cm}{0.4cm}}}
+ \put(0,1){\line(1,0){10}}
+
+ \pause
+
+ \put(4.6,2){{\color{lightyellow}\rule{0.4cm}{0.4cm}}}
+ \put(5.7,2){{\color{lightyellow}\rule{1.3cm}{0.4cm}}}
+ \put(7.7,2){{\color{lightyellow}\rule{0.4cm}{0.4cm}}}
+ \put(0,2){\line(1,0){10}}
+
+ \end{picture}
+ \end{center}
+
+\end{frame}
+
+\subsectionnonumber{Prioritäten \protect\color{darkgray}und Ressourcen}
+
+\begin{frame}
+
+ \showsection
+ \showsubsection
+
+ \only<4->{%
+ Der höher priorisierte Prozeß bewirkt selbst,\\
+ daß er eine Ressource verspätet bekommt.
+
+ \medskip
+
+ \textarrow\ \newterm{begrenzte Prioritätsinversion}
+
+ \medskip
+
+ maximale Verzögerung: Länge des kritischen Bereichs
+ }
+
+ \vspace{0cm plus 1filll}
+
+ \begin{center}
+ \begin{picture}(11,4)(-1,0)
+ \small
+
+ \put(-0.1,0.5){\vector(1,0){10.1}}
+ \put(9.75,0.4){\makebox(0,0)[tr]{Zeit}}
+ \put(0,0.4){\vector(0,1){3.6}}
+ \put(-0.1,3.75){\makebox(0,0)[tr]{Priorität}}
+
+ \put(1,3){{\color{lightorange}\rule{0.5cm}{0.4cm}}}
+ \only<1-2>{\put(3,3){{\color{lightorange}\rule{0.7cm}{0.4cm}}}}
+ \only<3->{\put(3,3){{\color{lightorange}\rule{0.4cm}{0.4cm}}}}
+ \only<3-4>{%
+ \put(3.4,3){{\color{red}\rule{0.8cm}{0.4cm}}}
+ \put(4.2,3){{\color{lightorange}\rule{0.2cm}{0.4cm}}}
+ {\thicklines
+ \put(3.3,2.95){\line(2,1){1.0}}
+ \put(3.3,3.45){\line(2,-1){1.0}}}
+ }
+ \only<5->{%
+ \put(3.9,3){{\color{red}\rule{0.8cm}{0.4cm}}}
+ \put(4.7,3){{\color{lightorange}\rule{0.2cm}{0.4cm}}}
+ }
+ \put(5,3){{\color{lightorange}\rule{0.6cm}{0.4cm}}}
+ \only<1-2>{%
+ \put(5.4,3){{\color{red}\rule{0.8cm}{0.4cm}}}
+ \put(6.2,3){{\color{lightorange}\rule{0.2cm}{0.4cm}}}
+ }
+ \put(7,3){{\color{lightorange}\rule{0.5cm}{0.4cm}}}
+ \put(9,3){{\color{lightorange}\rule{0.7cm}{0.4cm}}}
+ \put(0,3){\line(1,0){10}}
+
+ \only<2->{%
+ \put(0,1){{\color{lightgreen}\rule{1cm}{0.4cm}}}
+ \put(1.5,1){{\color{lightgreen}\rule{1.5cm}{0.4cm}}}
+ \put(2.6,1){{\color{medgreen}\rule{0.4cm}{0.4cm}}}
+ \only<2-4>{%
+ \put(3.7,1){{\color{medgreen}\rule{0.5cm}{0.4cm}}}
+ \put(4.2,1){{\color{lightgreen}\rule{0.3cm}{0.4cm}}}
+ }
+ \only<5->{%
+ \put(3.4,1){{\color{medgreen}\rule{0.5cm}{0.4cm}}}
+ \put(4.9,1){{\color{lightgreen}\rule{0.1cm}{0.4cm}}}
+ \put(5.6,1){{\color{lightgreen}\rule{0.2cm}{0.4cm}}}
+ }
+ \put(7.7,1){{\color{lightgreen}\rule{1.3cm}{0.4cm}}}
+ \put(9.7,1){{\color{lightgreen}\rule{0.3cm}{0.4cm}}}
+ \put(0,1){\line(1,0){10}}
+ }
+ \end{picture}
+ \end{center}
+
+\end{frame}
+
+\begin{frame}
+
+ \showsection
+ \showsubsection
+
+ \visible<4->{%
+ Ein Prozeß mit mittlerer Priorität bewirkt,
+ daß ein Prozeß mit hoher Priorität eine Ressource überhaupt nicht bekommt.
+
+ \medskip
+
+ \textarrow\ }\newterm{unbegrenzte Prioritätsinversion}
+
+ \pause
+ \vspace{0cm plus 1filll}
+
+ \begin{center}
+ \begin{picture}(11,4)(-1,0)
+ \small
+
+ \put(-0.1,0.5){\vector(1,0){10.1}}
+ \put(9.75,0.4){\makebox(0,0)[tr]{Zeit}}
+ \put(0,0.4){\vector(0,1){3.6}}
+ \put(-0.1,3.75){\makebox(0,0)[tr]{Priorität}}
+
+ \put(1,3){{\color{lightorange}\rule{0.5cm}{0.4cm}}}
+ \put(3,3){{\color{lightorange}\rule{0.4cm}{0.4cm}}}
+ \only<2>{%
+ \put(3.4,3){{\color{red}\rule{0.8cm}{0.4cm}}}
+ \put(4.2,3){{\color{lightorange}\rule{0.2cm}{0.4cm}}}
+ {\thicklines
+ \put(3.3,2.95){\line(2,1){1.0}}
+ \put(3.3,3.45){\line(2,-1){1.0}}}
+ \put(5,3){{\color{lightorange}\rule{0.6cm}{0.4cm}}}
+ \put(7,3){{\color{lightorange}\rule{0.5cm}{0.4cm}}}
+ \put(9,3){{\color{lightorange}\rule{0.7cm}{0.4cm}}}
+ }
+ \put(0,3){\line(1,0){10}}
+
+ \only<2->{%
+ \put(0,1){{\color{lightgreen}\rule{1cm}{0.4cm}}}
+ \put(1.5,1){{\color{lightgreen}\rule{1.1cm}{0.4cm}}}
+ \alt<1-4>{%
+ \put(2.6,1){{\color{medgreen}\rule{0.4cm}{0.4cm}}}
+ }{%
+ \put(2.6,1){{\color{medgreen}\rule{0.2cm}{0.4cm}}}
+ }
+ \only<2>{%
+ \put(3.7,1){{\color{medgreen}\rule{0.5cm}{0.4cm}}}
+ \put(4.2,1){{\color{lightgreen}\rule{0.3cm}{0.4cm}}}
+ }
+ \only<3-4>{%
+ \put(3.4,1){{\color{medgreen}\rule{0.5cm}{0.4cm}}}
+% \put(3.9,1){{\color{lightgreen}\rule{0.3cm}{0.4cm}}}
+ }
+ \only<2>{%
+ \put(7.7,1){{\color{lightgreen}\rule{1.3cm}{0.4cm}}}
+ \put(9.7,1){{\color{lightgreen}\rule{0.3cm}{0.4cm}}}
+ }
+ \put(0,1){\line(1,0){10}}
+ }
+
+ \only<5->{%
+ \put(2.8,2){{\color{lightyellow}\rule{0.2cm}{0.4cm}}}
+ \put(3.4,2){{\color{lightyellow}\rule{6.6cm}{0.4cm}}}
+ \put(0,2){\line(1,0){10}}
+ }
+ \end{picture}
+ \end{center}
+
+\end{frame}
+
+\begin{frame}
+
+ \showsection
+ \showsubsection
+
+ Ein Prozeß mit mittlerer Priorität bewirkt,
+ daß ein Prozeß mit hoher Priorität eine Ressource überhaupt nicht bekommt.
+
+ \medskip
+
+ \textarrow\ \newterm{unbegrenzte Prioritätsinversion}
+
+ \medskip
+
+ Beispiel: Beinahe-Verlust der Marssonde \emph{Pathfinder\/} im Juli 1997
+
+ \only<1>{%
+ \begin{center}
+ \includegraphics[width=8.7cm]{pathfinder.jpg}
+ \vspace*{-1.5cm}
+ \end{center}
+ }
+
+ \bigskip
+
+ \only<2>{%
+ Gegenmaßnahmen
+ \begin{itemize}
+ \item
+ \newterm{Priority Inheritance -- Prioritätsvererbung}\\
+ Der Besitzer des Mutex erbt die Priorität\\
+ des Prozesses, der auf den Mutex wartet.
+ \end{itemize}
+
+ \bigskip
+
+ \begin{minipage}{7.0cm}
+ \begin{flushright}
+ \url{http://research.microsoft.com/en-us/\\um/people/mbj/Mars\_Pathfinder/}
+ \end{flushright}
+ \end{minipage}
+
+ \vspace{1.35cm}\strut\hfill\makebox(0,0)[br]{\includegraphics[height=2.8cm]{pathfinder.jpg}}\vspace*{-1cm}
+ }
+
+\end{frame}
+
+\begin{frame}
+
+ \showsection
+ \showsubsection
+
+ Ein Prozeß mit mittlerer Priorität bewirkt,
+ daß ein Prozeß mit hoher Priorität eine Ressource überhaupt nicht bekommt.
+
+ \medskip
+
+ \textarrow\ \newterm{unbegrenzte Prioritätsinversion}
+
+ \bigskip
+
+ Gegenmaßnahme: \newterm{Priority Inheritance -- Prioritätsvererbung}
+
+ \vspace{0cm plus 1filll}
+
+ \begin{center}
+ \begin{picture}(11,4)(-1,0)
+ \small
+
+ \put(-0.1,0.5){\vector(1,0){10.1}}
+ \put(9.75,0.4){\makebox(0,0)[tr]{Zeit}}
+ \put(0,0.4){\vector(0,1){3.6}}
+ \put(-0.1,3.75){\makebox(0,0)[tr]{Priorität}}
+
+ \put(0,1){{\color{lightgreen}\rule{1cm}{0.4cm}}}
+ \put(1.5,1){{\color{lightgreen}\rule{1.1cm}{0.4cm}}}
+ \put(2.6,1){{\color{medgreen}\rule{0.2cm}{0.4cm}}}
+ \put(0,1){\line(1,0){10}}
+
+ \put(2.8,2){{\color{lightyellow}\rule{0.2cm}{0.4cm}}}
+ \only<1-2>{%
+ \put(3.4,2){{\color{lightyellow}\rule{6.6cm}{0.4cm}}}
+ }
+ \put(0,2){\line(1,0){10}}
+
+ \put(1,3){{\color{lightorange}\rule{0.5cm}{0.4cm}}}
+ \put(3,3){{\color{lightorange}\rule{0.4cm}{0.4cm}}}
+ \put(0,3){\line(1,0){10}}
+
+ \only<2>{%
+ \put(3.4,3){{\color{red}\rule{0.8cm}{0.4cm}}}
+ {\thicklines
+ \put(3.3,2.95){\line(2,1){1.0}}
+ \put(3.3,3.45){\line(2,-1){1.0}}}
+ }
+
+ \only<3->{%
+ \put(3.4,3){{\color{medgreen}\rule{0.7cm}{0.4cm}}}
+ \put(4.1,3){{\color{red}\rule{0.8cm}{0.4cm}}}
+ \put(5.7,2){{\color{lightyellow}\rule{1.3cm}{0.4cm}}}
+ \put(4.9,3){{\color{lightorange}\rule{0.8cm}{0.4cm}}}
+ \put(7,3){{\color{lightorange}\rule{0.5cm}{0.4cm}}}
+ \put(7.5,2){{\color{lightyellow}\rule{1.5cm}{0.4cm}}}
+ \put(9,3){{\color{lightorange}\rule{0.7cm}{0.4cm}}}
+ \put(9.7,2){{\color{lightyellow}\rule{0.3cm}{0.4cm}}}
+ }
+ \end{picture}
+ \end{center}
+
+\end{frame}
+
+\begin{frame}
+
+ \showsection
+ \showsubsection
+
+ Ein Prozeß mit mittlerer Priorität bewirkt,
+ daß ein Prozeß mit hoher Priorität eine Ressource überhaupt nicht bekommt.
+
+ \medskip
+
+ \textarrow\ \newterm{unbegrenzte Prioritätsinversion}
+
+ \bigskip
+
+ Gegenmaßnahme: \newterm{Priority Ceiling -- Prioritätsobergrenze}
+
+ \vspace{0cm plus 1filll}
+
+ \begin{center}
+ \begin{picture}(11,4)(-1,0)
+ \small
+
+ \put(-0.1,0.5){\vector(1,0){10.1}}
+ \put(9.75,0.4){\makebox(0,0)[tr]{Zeit}}
+ \put(0,0.4){\vector(0,1){3.6}}
+ \put(-0.1,3.75){\makebox(0,0)[tr]{Priorität}}
+
+ \put(0,1){{\color{lightgreen}\rule{1cm}{0.4cm}}}
+ \put(1.5,1){{\color{lightgreen}\rule{1.1cm}{0.4cm}}}
+% \only<1>{%
+% \put(2.6,1){{\color{medgreen}\rule{0.2cm}{0.4cm}}}
+% }
+ \put(0,1){\line(1,0){10}}
+
+% \only<1>{%
+% \put(2.8,2){{\color{lightyellow}\rule{0.2cm}{0.4cm}}}
+% \put(3.4,2){{\color{lightyellow}\rule{6.6cm}{0.4cm}}}
+% }
+ \put(0,2){\line(1,0){10}}
+
+ \put(1,3){{\color{lightorange}\rule{0.5cm}{0.4cm}}}
+% \only<1>{%
+% \put(3,3){{\color{lightorange}\rule{0.4cm}{0.4cm}}}
+% }
+ \put(0,3){\line(1,0){10}}
+
+% \only<2>{%
+% \only<2>{%
+ \put(2.6,3){{\color{medgreen}\rule{0.9cm}{0.4cm}}}
+ \put(3.5,3){{\color{lightorange}\rule{0.4cm}{0.4cm}}}
+ \put(3.9,3){{\color{red}\rule{0.8cm}{0.4cm}}}
+ \put(4.7,3){{\color{lightorange}\rule{0.8cm}{0.4cm}}}
+ \put(5.5,2){{\color{lightyellow}\rule{1.5cm}{0.4cm}}}
+ \put(7,3){{\color{lightorange}\rule{0.5cm}{0.4cm}}}
+ \put(7.5,2){{\color{lightyellow}\rule{1.5cm}{0.4cm}}}
+ \put(9,3){{\color{lightorange}\rule{0.7cm}{0.4cm}}}
+ \put(9.7,2){{\color{lightyellow}\rule{0.3cm}{0.4cm}}}
+% }
+ \end{picture}
+ \end{center}
+
+\end{frame}
+
+\begin{frame}
+
+ \showsection
+ \showsubsection
+
+ Ein Prozeß mit mittlerer Priorität bewirkt,
+ daß ein Prozeß mit hoher Priorität eine Ressource überhaupt nicht bekommt.
+
+ \medskip
+
+ \textarrow\ \newterm{unbegrenzte Prioritätsinversion}
+
+ \medskip
+
+ Beispiel: Beinahe-Verlust der Marssonde \emph{Pathfinder\/} im Juli 1997
+
+ \bigskip
+
+ Gegenmaßnahmen
+ \begin{itemize}
+ \item
+ \newterm{Priority Inheritance -- Prioritätsvererbung}\\
+ Der Besitzer des Mutex erbt die Priorität\\
+ des Prozesses, der auf den Mutex wartet.
+ \smallskip
+ \item
+ \newterm{Priority Ceiling -- Prioritätsobergrenze}\\
+ Der Besitzer des Mutex bekommt sofort\\
+ die Priorität des höchstmöglichen Prozesses,\\
+ der evtl.\ den Mutex benötigen könnte.
+ \pause
+ \begin{picture}(0,0)
+ \put(1.2,1.45){\makebox(0,0)[l]{$\left\}\rule{0pt}{1.7cm}\right.$
+ \begin{minipage}{4cm}
+ nur möglich, wenn\\
+ Mutexe im Spiel sind
+ \end{minipage}}}
+ \end{picture}
+ \smallskip
+ \pause
+ \item
+ \newterm{Priority Aging}\\
+ Die Priorität wächst mit der Wartezeit.
+ \end{itemize}
+ \vspace*{-1cm}
+
+\end{frame}
+
+\nosectionnonumber{Vertiefung Systemtechnik -- Eingebettete Systeme}
+
+\begin{frame}
+
+ \shownosectionnonumber
+
+ \begin{itemize}
+ \item[\textbf{1}] \textbf{Einführung}
+ \hfill\makebox(0,0)[br]{\raisebox{2.25ex}{\url{https://gitlab.cvh-server.de/pgerwinski/es.git}}}%
+ \item[\textbf{2}] \textbf{Einführung in Unix}
+ \item[\textbf{3}] \textbf{TCP/IP in der Praxis}
+ \item[\textbf{4}] \textbf{Bus-Systeme}
+ \begin{itemize}
+ \color{medgreen}
+ \item[4.1] Was sind Bus-Systeme?
+ \item[4.2] RS-232
+ \item[4.3] \ItwoC\ (TWI)
+ \item[4.4] SPI
+ \item[4.5] Beispiel: Benutzung des \ItwoC-Busses
+ \end{itemize}
+ \item[\textbf{5}] \textbf{Echtzeit}
+ \begin{itemize}
+ \color{medgreen}
+ \item[5.1] Was ist Echtzeit?
+ \item[5.2] Echtzeitprogrammierung
+ \item[5.3] Multitasking
+ \item[5.4] Ressourcen
+ \item[5.5] Prioritäten
+ \end{itemize}
+ \vspace*{-\smallskipamount}
+ \item[\textbf{\dots}]
+ \underconstruction
+ \end{itemize}
+
+\end{frame}
+
+\end{document}
diff --git a/20171116/herzschrittmacher.jpg b/20171116/herzschrittmacher.jpg
new file mode 120000
index 0000000000000000000000000000000000000000..92d8f0053003cc555aec83f5d088f1cec822ad81
--- /dev/null
+++ b/20171116/herzschrittmacher.jpg
@@ -0,0 +1 @@
+../common/herzschrittmacher.jpg
\ No newline at end of file
diff --git a/20171116/kompass-messung.png b/20171116/kompass-messung.png
new file mode 120000
index 0000000000000000000000000000000000000000..85cfa0d3840e7542ebb6dd2092be6c2a6e08fbb1
--- /dev/null
+++ b/20171116/kompass-messung.png
@@ -0,0 +1 @@
+../common/kompass-messung.png
\ No newline at end of file
diff --git a/20171116/kompassmodul-an-roboter.jpg b/20171116/kompassmodul-an-roboter.jpg
new file mode 120000
index 0000000000000000000000000000000000000000..dab8b38c1a92bf8072d42dc3abcc07be54a58c7b
--- /dev/null
+++ b/20171116/kompassmodul-an-roboter.jpg
@@ -0,0 +1 @@
+../common/kompassmodul-an-roboter.jpg
\ No newline at end of file
diff --git a/20171116/kompassmodul.jpg b/20171116/kompassmodul.jpg
new file mode 120000
index 0000000000000000000000000000000000000000..be108a5341df13a693959dbe69b7b9541b36fc4c
--- /dev/null
+++ b/20171116/kompassmodul.jpg
@@ -0,0 +1 @@
+../common/kompassmodul.jpg
\ No newline at end of file
diff --git a/20171116/logo-hochschule-bochum-cvh-text.pdf b/20171116/logo-hochschule-bochum-cvh-text.pdf
new file mode 120000
index 0000000000000000000000000000000000000000..a05946126bc0ce6a2818740da2893f59eb0c659c
--- /dev/null
+++ b/20171116/logo-hochschule-bochum-cvh-text.pdf
@@ -0,0 +1 @@
+../common/logo-hochschule-bochum-cvh-text.pdf
\ No newline at end of file
diff --git a/20171116/logo-hochschule-bochum.pdf b/20171116/logo-hochschule-bochum.pdf
new file mode 120000
index 0000000000000000000000000000000000000000..b6b9491e370e499c9276918182cdb82cb311bcd1
--- /dev/null
+++ b/20171116/logo-hochschule-bochum.pdf
@@ -0,0 +1 @@
+../common/logo-hochschule-bochum.pdf
\ No newline at end of file
diff --git a/20171116/make-zombies.c b/20171116/make-zombies.c
new file mode 100644
index 0000000000000000000000000000000000000000..3e1418aa5567a38d274cbb2ba1588d7e765823d4
--- /dev/null
+++ b/20171116/make-zombies.c
@@ -0,0 +1,39 @@
+#include <sys/wait.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+int main(void){
+ pid_t pids[10]; // Platz f�r 10 Prozess-IDs (die Kindprozesse)
+ int i; // Laufvariable
+
+ for (i = 0; i < 10; ++i) {
+ // Der Vaterprozess erzeugt nun einen Kindprozess,
+ // welcher unabh�ngig vom Vaterprozess mit der
+ // erneuten Ausf�hrung des Programms beginnt.
+ // Ein Kindprozess erzeugt keinen Fork von sich selbst.
+ pids[i] = fork();
+ if (pids[i] == 0) {
+ // dann befinden wir uns in einem der 10 Kindprozesse
+ // Der erste Kindprozess wartet 10 Sekunden und jeder
+ // weitere Kindprozess wartet 1 Sekunde k�rzer als der
+ // vorige.
+ printf ("BRAINS! ");
+ sleep(10-i);
+ exit(0); // Kindprozess erfolgreich beenden
+ }
+ }
+/*
+ // hier kommt nur der Vaterprozess vorbei
+ for (i = 0; i < 10; ++i){
+ // Der Vaterprozess wartet nun, bis der Reihe nach jeder
+ // seiner 10 Kindprozesse beendet ist. Leider wird auf das
+ // Kind mit der l�ngsten Wartezeit zuerst gewartet. Obwohl
+ // die anderen Kinder l�ngst erfolgreich beendet wurden,
+ // blockiert das erste Kind eine Bereinigung der Prozesstabelle
+ waitpid(pids[i], NULL, 0);
+ }
+*/
+ while (1);
+ return 0; // Vaterprozess erfolgreich beenden
+}
diff --git a/20171116/motherboard-anschluesse.jpg b/20171116/motherboard-anschluesse.jpg
new file mode 120000
index 0000000000000000000000000000000000000000..07335d7dff65c71a683588d2ed108485c4653fb7
--- /dev/null
+++ b/20171116/motherboard-anschluesse.jpg
@@ -0,0 +1 @@
+../common/motherboard-anschluesse.jpg
\ No newline at end of file
diff --git a/20171116/pathfinder.jpg b/20171116/pathfinder.jpg
new file mode 120000
index 0000000000000000000000000000000000000000..23c6444fee26e0cf0dd2f8639484b00aa5021b59
--- /dev/null
+++ b/20171116/pathfinder.jpg
@@ -0,0 +1 @@
+../common/pathfinder.jpg
\ No newline at end of file
diff --git a/20171116/pgslides.sty b/20171116/pgslides.sty
new file mode 120000
index 0000000000000000000000000000000000000000..5be1416f4216f076aa268901f52a15d775e43f64
--- /dev/null
+++ b/20171116/pgslides.sty
@@ -0,0 +1 @@
+../common/pgslides.sty
\ No newline at end of file
diff --git a/20171116/philosophenproblem.jpg b/20171116/philosophenproblem.jpg
new file mode 120000
index 0000000000000000000000000000000000000000..26591b2ac2dddfd4786814baf3f19ecb67f1f5ee
--- /dev/null
+++ b/20171116/philosophenproblem.jpg
@@ -0,0 +1 @@
+../common/philosophenproblem.jpg
\ No newline at end of file
diff --git a/20171116/photo-20171116-152713.jpg b/20171116/photo-20171116-152713.jpg
new file mode 100644
index 0000000000000000000000000000000000000000..5dcca28aba3dab5d07c1e6e638ed696ed05f03e2
Binary files /dev/null and b/20171116/photo-20171116-152713.jpg differ
diff --git a/20171116/quadrocopter.jpg b/20171116/quadrocopter.jpg
new file mode 120000
index 0000000000000000000000000000000000000000..7eaf0c024b63b7bc1dd3df2c17c8ab93f67fc15c
--- /dev/null
+++ b/20171116/quadrocopter.jpg
@@ -0,0 +1 @@
+../common/quadrocopter.jpg
\ No newline at end of file
diff --git a/20171116/rp6.jpg b/20171116/rp6.jpg
new file mode 120000
index 0000000000000000000000000000000000000000..2a0ecff23845770c3a98178eca6dce3ec73aca58
--- /dev/null
+++ b/20171116/rp6.jpg
@@ -0,0 +1 @@
+../common/rp6.jpg
\ No newline at end of file
diff --git a/20171116/rs-232.pdf b/20171116/rs-232.pdf
new file mode 100644
index 0000000000000000000000000000000000000000..236ef5bf182048842613c5416b91afb68f451fa6
Binary files /dev/null and b/20171116/rs-232.pdf differ
diff --git a/20171116/rs-232.tex b/20171116/rs-232.tex
new file mode 100644
index 0000000000000000000000000000000000000000..a174692f177abe0d0ff1afd7e6783160485b5a22
--- /dev/null
+++ b/20171116/rs-232.tex
@@ -0,0 +1,97 @@
+% rs-232.pdf - Illustration of the RS-232 Protocol
+% Copyright (C) 2011, 2016 Peter Gerwinski
+%
+% based on http://de.wikipedia.org/w/index.php?title=Datei:RS-232_timing.png&filetimestamp=20050719153204
+% Copyright (C) 2005 Wikipedia-Autor Gerald.deppe, released into Public Domain
+%
+% This document is free software: you can redistribute it and/or
+% modify it either under the terms of the Creative Commons
+% Attribution-ShareAlike 3.0 License, or under the terms of the
+% GNU General Public License as published by the Free Software
+% Foundation, either version 3 of the License, or (at your option)
+% any later version.
+%
+% This document is distributed in the hope that it will be useful,
+% but WITHOUT ANY WARRANTY; without even the implied warranty of
+% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+% GNU General Public License for more details.
+%
+% You should have received a copy of the GNU General Public License
+% along with this document. If not, see <http://www.gnu.org/licenses/>.
+%
+% You should have received a copy of the Creative Commons
+% Attribution-ShareAlike 3.0 Unported License along with this
+% document. If not, see <http://creativecommons.org/licenses/>.
+
+\documentclass[10pt,t]{beamer}
+
+\usepackage{pgslides}
+\usepackage{rotating}
+
+\setbeamertemplate{footline}{}
+
+\begin{document}
+
+\begin{frame}
+ \vspace*{-0.65cm}
+ \begin{center}
+ \includegraphics[width=12cm]{RS-232_timing-no-text.png}\\
+ \begin{picture}(12,1)
+ \footnotesize
+ \put(0.1,9.17){\mbox{Synchronisation}}
+ \put(0.1,8.77){\mbox{Daten}}
+ \put(0.1,8.37){\mbox{Check}}
+% \put(3,8.77){\mbox{9600\,8O1 = 9600\,Baud, 8 Daten-Bits, ungerade Parität (odd), 1 Stopp-Bit}}
+ \put(3,9.17){\mbox{9600\,Baud, 8 Daten-Bits, ungerade Parität, 1 Stopp-Bit}}
+ \put(3,8.77){\mbox{Beispiel-Daten: ASCII "`G"' = 71 = 0100\,0111 binär}}
+ \put(3,8.37){\mbox{Übertragung der Daten von rechts (Bit 0) nach links (Bit 7)}}
+ \put(2.000,6.4){\begin{rotate}{90}Ruhe\end{rotate}}
+ \put(2.900,6.4){\begin{rotate}{90}Start-Bit\end{rotate}}
+% \put(3.569,6.4){\begin{rotate}{90}LSB 0\end{rotate}}
+ \put(3.569,6.4){\begin{rotate}{90}Bit 0\end{rotate}}
+ \put(4.238,6.4){\begin{rotate}{90}Bit 1\end{rotate}}
+ \put(4.907,6.4){\begin{rotate}{90}Bit 2\end{rotate}}
+ \put(5.576,6.4){\begin{rotate}{90}Bit 3\end{rotate}}
+ \put(6.245,6.4){\begin{rotate}{90}Bit 4\end{rotate}}
+ \put(6.914,6.4){\begin{rotate}{90}Bit 5\end{rotate}}
+ \put(7.583,6.4){\begin{rotate}{90}Bit 6\end{rotate}}
+% \put(8.252,6.4){\begin{rotate}{90}MSB 7\end{rotate}}
+ \put(8.252,6.4){\begin{rotate}{90}Bit 7\end{rotate}}
+ \put(8.921,6.4){\begin{rotate}{90}Parität\end{rotate}}
+ \put(9.590,6.4){\begin{rotate}{90}Stopp-Bit\end{rotate}}
+ \put(10.09175,6.4){\begin{rotate}{90}Ruhe\end{rotate}}
+ \put(10.5935,6.4){\begin{rotate}{90}Start-Bit\end{rotate}}
+ \put(11.2625,6.4){\begin{rotate}{90}\dots\end{rotate}}
+ \put(2.000,4.4){\makebox(0,0)[br]{1}}
+ \put(2.900,4.4){\makebox(0,0)[br]{0}}
+ \put(3.569,4.4){\makebox(0,0)[br]{1}}
+ \put(4.238,4.4){\makebox(0,0)[br]{1}}
+ \put(4.907,4.4){\makebox(0,0)[br]{1}}
+ \put(5.576,4.4){\makebox(0,0)[br]{0}}
+ \put(6.245,4.4){\makebox(0,0)[br]{0}}
+ \put(6.914,4.4){\makebox(0,0)[br]{0}}
+ \put(7.583,4.4){\makebox(0,0)[br]{1}}
+ \put(8.252,4.4){\makebox(0,0)[br]{0}}
+ \put(8.921,4.4){\makebox(0,0)[br]{1}}
+ \put(9.590,4.4){\makebox(0,0)[br]{1}}
+ \put(10.09175,4.4){\makebox(0,0)[br]{1}}
+ \put(10.5935,4.4){\makebox(0,0)[br]{0}}
+ \put(0.1,5.60){\mbox{logisch 1}}
+ \put(0.1,5.20){\mbox{logisch 0}}
+ \put(1,3.8){\makebox(0,0)[r]{$\sf +15$\,V}}
+ \put(1,2.8){\makebox(0,0)[r]{$\sf +3$\,V}}
+ \put(1,2.5){\makebox(0,0)[r]{$\sf 0$\,V}}
+ \put(1,2.2){\makebox(0,0)[r]{$\sf -3$\,V}}
+ \put(1,1.2){\makebox(0,0)[r]{$\sf -15$\,V}}
+ \put(1.2,0.6){\vector(1,0){9.6}}
+ \put(10.8,0.3){\makebox(0,0)[tr]{Zeit/s}}
+ \multiput(2.45,0.6)(0.669,0){13}{\line(0,-1){0.1}}
+ \put(2.45,0.4){\makebox(0,0)[t]{\sf 0}}
+ \put(3.119,0.4){\makebox(0,0)[t]{$\sf\frac{1}{9600}$}}
+ \put(5.795,0,4){\makebox(0,0)[t]{$\sf\frac{5}{9600}$}}
+ \put(9.140,0,4){\makebox(0,0)[t]{$\sf\frac{10}{9600}$}}
+ \end{picture}
+ \end{center}
+\end{frame}
+
+\end{document}
diff --git a/20171116/xbee.jpg b/20171116/xbee.jpg
new file mode 120000
index 0000000000000000000000000000000000000000..ff0adff2eadf3d9b775d03cea8cf1f118534e2b9
--- /dev/null
+++ b/20171116/xbee.jpg
@@ -0,0 +1 @@
+../common/xbee.jpg
\ No newline at end of file
diff --git a/20171123/Retribution_Engine_Screenshot_120807.jpg b/20171123/Retribution_Engine_Screenshot_120807.jpg
new file mode 120000
index 0000000000000000000000000000000000000000..19f4cb3e4aae1e24c3466a25b2c0e5ad90ee49e7
--- /dev/null
+++ b/20171123/Retribution_Engine_Screenshot_120807.jpg
@@ -0,0 +1 @@
+../common/Retribution_Engine_Screenshot_120807.jpg
\ No newline at end of file
diff --git a/20171123/Telefon_t-sinus-700.jpg b/20171123/Telefon_t-sinus-700.jpg
new file mode 120000
index 0000000000000000000000000000000000000000..27c322c50b0f05edc8b07cfb0cc99b1876eb506d
--- /dev/null
+++ b/20171123/Telefon_t-sinus-700.jpg
@@ -0,0 +1 @@
+../common/Telefon_t-sinus-700.jpg
\ No newline at end of file
diff --git a/20171123/Zeichen_123.pdf b/20171123/Zeichen_123.pdf
new file mode 120000
index 0000000000000000000000000000000000000000..fdbc897227df059cfda790a16555e6e417682116
--- /dev/null
+++ b/20171123/Zeichen_123.pdf
@@ -0,0 +1 @@
+../common/Zeichen_123.pdf
\ No newline at end of file
diff --git a/20171123/a380.jpg b/20171123/a380.jpg
new file mode 120000
index 0000000000000000000000000000000000000000..33a5d1fd18843bf7385e5a6d90f69af9fd8720da
--- /dev/null
+++ b/20171123/a380.jpg
@@ -0,0 +1 @@
+../common/a380.jpg
\ No newline at end of file
diff --git a/20171123/curiosity.jpg b/20171123/curiosity.jpg
new file mode 120000
index 0000000000000000000000000000000000000000..4452844da537414b751c5283ca8468b3ced9afb3
--- /dev/null
+++ b/20171123/curiosity.jpg
@@ -0,0 +1 @@
+../common/curiosity.jpg
\ No newline at end of file
diff --git a/20171123/dsc_8208.jpg b/20171123/dsc_8208.jpg
new file mode 120000
index 0000000000000000000000000000000000000000..5796341ebc774aa09965a3a29854c65ce1144fb8
--- /dev/null
+++ b/20171123/dsc_8208.jpg
@@ -0,0 +1 @@
+../common/dsc_8208.jpg
\ No newline at end of file
diff --git a/20171123/env.cgi b/20171123/env.cgi
new file mode 100755
index 0000000000000000000000000000000000000000..221c600b2510c4847b16c33db2788a13ce1a5549
--- /dev/null
+++ b/20171123/env.cgi
@@ -0,0 +1,20 @@
+#!/bin/bash
+
+echo Content-Type: text/plain
+echo
+
+echo "Hello, world!"
+echo
+
+echo "Hier meine Eingabedaten:"
+echo
+cat
+echo
+echo
+
+echo "Hier meine Umgebungsvariablen:"
+echo
+set
+echo
+
+echo "Tschüs!"
diff --git a/20171123/es-20171123.pdf b/20171123/es-20171123.pdf
new file mode 100644
index 0000000000000000000000000000000000000000..e90c6ca2c57135ab8eed85c595f76600d7a12709
Binary files /dev/null and b/20171123/es-20171123.pdf differ
diff --git a/20171123/es-20171123.tex b/20171123/es-20171123.tex
new file mode 100644
index 0000000000000000000000000000000000000000..ac929c8483ed39923262f612207fe82a61247ec0
--- /dev/null
+++ b/20171123/es-20171123.tex
@@ -0,0 +1,1522 @@
+% es-20171123.pdf - Lecture Slides on Embedded Systems
+% Copyright (C) 2013, 2014, 2015, 2016, 2017 Peter Gerwinski
+%
+% This document is free software: you can redistribute it and/or
+% modify it either under the terms of the Creative Commons
+% Attribution-ShareAlike 3.0 License, or under the terms of the
+% GNU General Public License as published by the Free Software
+% Foundation, either version 3 of the License, or (at your option)
+% any later version.
+%
+% This document is distributed in the hope that it will be useful,
+% but WITHOUT ANY WARRANTY; without even the implied warranty of
+% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+% GNU General Public License for more details.
+%
+% You should have received a copy of the GNU General Public License
+% along with this document. If not, see <http://www.gnu.org/licenses/>.
+%
+% You should have received a copy of the Creative Commons
+% Attribution-ShareAlike 3.0 Unported License along with this
+% document. If not, see <http://creativecommons.org/licenses/>.
+
+% README: Bus-Systeme, evtl. Echtzeit
+
+\documentclass[10pt,t]{beamer}
+
+\usepackage{pgslides}
+\usepackage{rotating}
+\usepackage{tikz}
+\usepackage[obeyfamily=false,mathrm=mathsf,textrm=sffamily]{siunitx}
+
+\newrgbcolor{lightyellow}{0.95 0.85 0.0}
+\newrgbcolor{lightorange}{1.0 0.7 0.0}
+\newrgbcolor{lightgreen}{0.0 0.8 0.0}
+
+\newcommand{\underconstruction}{\vspace*{-5cm plus 1filll}%
+ \begin{picture}(0,0)
+ \put(9,1.3){\makebox(0,0)[b]{\includegraphics[width=1.5cm]{Zeichen_123.pdf}}}
+ \put(9,1.0){\makebox(0,0)[t]{\shortstack{Änderungen\\vorbehalten}}}
+ \end{picture}}
+
+\title{Vertiefung Systemtechnik\\Eingebettete Systeme}
+\author{Prof.\ Dr.\ rer.\ nat.\ Peter Gerwinski}
+\date{23.\ November 2017}
+
+\newcommand{\ItwoC}{I\raisebox{0.5ex}{\footnotesize 2}C}
+
+\begin{document}
+
+\newlength{\normalpdfpageheight}
+\setlength{\normalpdfpageheight}{\pdfpageheight}
+
+\maketitleframe
+
+\nosectionnonumber{Vertiefung Systemtechnik -- Eingebettete Systeme}
+
+\begin{frame}
+
+ \shownosectionnonumber
+
+ \begin{itemize}
+ \item[\textbf{1}] \textbf{Einführung}
+ \hfill\makebox(0,0)[br]{\raisebox{2.25ex}{\url{https://gitlab.cvh-server.de/pgerwinski/es.git}}}%
+ \item[\textbf{2}] \textbf{Einführung in Unix}
+ \item[\textbf{3}] \textbf{TCP/IP in der Praxis}
+ \item[\textbf{4}] \textbf{Bus-Systeme}
+ \item[\textbf{6}] \textbf{Echtzeit}
+ \begin{itemize}
+ \item[5.1] Was ist Echtzeit?
+ \item[5.2] Echtzeitprogrammierung
+ \item[5.3] Multitasking
+ \color{medgreen}
+ \item[5.4] Ressourcen
+ \item[5.5] Prioritäten
+ \color{red}
+ \item[5.6] Echtzeitbetriebssysteme
+ \end{itemize}
+ \item[\textbf{6}] \textbf{Web-Interfaces}
+ \begin{itemize}
+ \color{red}
+ \item[6.1] HTTP, HTML und CGI
+ \item[6.2] Externe CGI-Skripte, GET und POST
+ \item[6.3] Skript im Server: PHP
+ \item[6.4] Server im Skript: Twisted
+ \end{itemize}
+ \vspace*{-\smallskipamount}
+ \item[\textbf{\dots}]
+ \underconstruction
+ \end{itemize}
+
+\end{frame}
+
+\setcounter{section}{4}
+\section{Echtzeit}
+\setcounter{subsection}{3}
+\subsection{Ressourcen}
+
+\begin{frame}
+
+ \showsection
+ \showsubsection
+
+ Ressourcen reservieren
+ \begin{itemize}
+ \item
+ \newterm{Semaphor}\\
+ gemeinsame Variable mehrerer Prozesse\\
+ zur Regelung des Zugriffs auf eine Ressource\\[\smallskipamount]
+ Ressource belegt \textarrow\ Kontextwechsel
+ \begin{onlyenv}<1>
+ \par\medskip
+ griechisch: \emph{sema\/} -- Zeichen, \emph{pherein\/} -- tragen\\
+ "`Eisenbahnsignal"'
+ \vspace*{-3cm}
+ \end{onlyenv}
+ \pause
+ \medskip
+ \item
+ \newterm{Mutex}\\
+ Mechanismus, damit immer nur ein Prozeß gleichzeitig\\
+ auf eine Ressource zugreifen kann
+ \begin{onlyenv}<2>
+ \par\medskip
+ englisch: \emph{mutual exclusion\/} -- wechselseitiger Ausschluß\\
+ spezieller binärer Semaphor: nur "`Besitzer"' darf freigeben\\
+ % allgemein: auch jemand anderer dürfte freigeben
+ \vspace*{-3cm}
+ \end{onlyenv}
+ \pause
+ \medskip
+ \item
+ \newterm{Spinlock} (\emph{busy waiting\/})\\
+ leichtgewichtige Alternative zu Kontextwechsel
+ \begin{onlyenv}<3>
+ \par\medskip
+ englisch: \emph{spin\/} -- rotieren, \emph{lock\/} Sperre\\
+ \emph{busy waiting} auf etwas Schnelles, z.\,B.\ auf einen Semaphor\\[\medskipamount]
+ Hardware-Unterstützung:
+ Prüfen, ob Variable bestimmten Wert hat;\\
+ wenn ja, auf anderen Wert setzen; andere Prozessoren solange anhalten
+ \vspace*{-3cm}
+ \end{onlyenv}
+ \pause
+ \medskip
+ \item
+ \newterm{Kritischer Abschnitt -- critical section}\\
+ Programmabschnitt zwischen Reservierung\\
+ und Freigabe einer Ressource\\
+ \textarrow\ sollte immer so kurz wie möglich sein
+ \end{itemize}
+ \vspace*{-1cm}
+
+\end{frame}
+
+\begin{frame}
+
+ \showsection
+ \showsubsection
+
+ Ressourcen reservieren --
+ Beispiel: \file{linux-3.7rc1}
+ \begin{itemize}
+ \item
+ \newterm{Semaphor}\\
+ \file{kernel/semaphor.c}\\
+ \file{drivers/usb/core/file.c}
+ \medskip
+ \item
+ \newterm{Mutex}\\
+ \file{kernel/mutex.c}\\
+ \file{drivers/usb/serial/usb-serial.c}
+ \medskip
+ \item
+ \newterm{Spinlock}\\
+ \file{kernel/spinlock.c}\\
+ \file{kernel/semaphor.c},
+ \file{kernel/mutex.c}
+ \end{itemize}
+
+ % Aufgabe: Anwendungsarten im MultiWii- und RP6-Code identifizieren
+
+ % evtl. Aufgabe: Warte-Problem
+
+ % Aufgabe: Wie lösen bekannte Multitasking-Betriebssysteme
+ % das o.a. Zuteilungsproblem?
+
+ % Danach: Semaphoren, Mutexe, Spinlocks
+ % Priorisierungsmethoden und -probleme
+
+ % Festplatten: completely fair queueing
+ % cat /sys/block/sdc/queue/scheduler
+ % "noop" hat sich für SVG gelohnt
+
+ % Virtualisierung + Kernel-Threads + Multiprozessorsystem = Chaos
+
+\end{frame}
+
+\begin{frame}[fragile]
+
+ \textbf{Beispiel:}
+ \lstinline{usb_serial_get_by_index()} -- serielle Schnittstelle reservieren
+
+ Datei \file{linux-3.7-rc1/drivers/usb/serial/usb-serial.c}, ab Zeile 62
+
+ \medskip
+
+ \begin{lstlisting}
+ struct usb_serial *usb_serial_get_by_index (unsigned index)
+ {
+ struct usb_serial *serial;
+ mutex_lock (&table_lock);
+ serial = serial_table[index];
+ if (serial)
+ {
+ mutex_lock (&serial->disc_mutex);
+ if (serial->disconnected)
+ {
+ mutex_unlock (&serial->disc_mutex);
+ serial = NULL;
+ }
+ else
+ kref_get (&serial->kref);
+ }
+ mutex_unlock (&table_lock);
+ return serial;
+ }
+ \end{lstlisting}
+ \begin{picture}(0,0)
+ \color{red}
+ \put(5.1,6.85){\vector(-1,0){0.5}}
+ \put(5.2,6.85){\makebox(0,0)[l]{exklusiven Zugriff auf Tabelle sichern}}
+ \put(5.4,1.35){\vector(-1,0){0.5}}
+ \put(5.5,1.35){\makebox(0,0)[l]{\shortstack[l]{exklusiven Zugriff auf Tabelle\\wieder freigeben}}}
+ \end{picture}
+
+\end{frame}
+
+\setlength{\pdfpageheight}{48cm}
+
+\begin{frame}[fragile]
+
+ \lstinline{mutex_lock()} -- Ressource beanspruchen, notfalls warten
+
+ Datei \file{linux-3.7-rc1/drivers/usb/serial/usb-serial.c}, ab Zeile 62
+
+ \medskip
+
+ \begin{lstlisting}
+ void __sched mutex_lock (struct mutex *lock)
+ {
+ might_sleep ();
+ __mutex_fastpath_lock (&lock->count, __mutex_lock_slowpath);
+ mutex_set_owner (lock);
+ }
+ \end{lstlisting}
+ \begin{picture}(0,0)
+ \color{red}
+ \put(11.6,1.35){\line(-1,0){1}}
+ \put(11.6,1.35){\line(0,-1){2.45}}
+ \put(11.6,-1.10){\vector(-1,0){2.0}}
+ \end{picture}
+
+ \bigskip
+
+ Datei \file{linux-3.7-rc1/arch/x86/include/asm/mutex\_32.h}, ab Zeile 24
+
+ Macro-Definition für \lstinline{__mutex_fastpath_lock} (expandiert)
+
+ \medskip
+
+ Assembler:
+ \begin{lstlisting}[language={[x86masm]Assembler}]
+ lock dec (lock->count)
+ jns 1
+ call __mutex_lock_slowpath
+ 1:
+ \end{lstlisting}
+ \begin{picture}(0,0)
+ \color{red}
+ \put(9,0.95){\line(-1,0){3.5}}
+ \put(9,0.95){\line(0,-1){2.5}}
+ \put(9.0,-1.55){\vector(-1,0){1.0}}
+ \end{picture}
+
+ \bigskip
+
+ Datei \file{linux-3.7-rc1/kernel/mutex.c}, ab Zeile 398
+
+ \medskip
+
+ \begin{lstlisting}
+ static __used noinline void __sched
+ __mutex_lock_slowpath (atomic_t *lock_count)
+ {
+ struct mutex *lock = container_of (lock_count, struct mutex, count);
+ __mutex_lock_common (lock, TASK_UNINTERRUPTIBLE, 0,
+ NULL, _RET_IP_);
+ }
+ \end{lstlisting}
+ \begin{picture}(0,0)
+ \color{red}
+ \put(11.0,1.40){\line(-1,0){1.0}}
+ \put(11.0,1.40){\vector(0,-1){2.5}}
+ \end{picture}
+
+ \bigskip
+
+ Datei \file{linux-3.7-rc1/kernel/mutex.c}, ab Zeile 132
+
+ \medskip
+
+ \begin{lstlisting}
+ static inline int __sched
+ __mutex_lock_common (struct mutex *lock, long state, unsigned int subclass,
+ struct lockdep_map *nest_lock, unsigned long ip)
+ {
+ struct task_struct *task = current;
+ struct mutex_waiter waiter;
+ unsigned long flags;
+
+ preempt_disable ();
+ mutex_acquire_nest (&lock->dep_map, subclass, 0, nest_lock, ip);
+
+ /* ... */
+
+ spin_lock_mutex (&lock->wait_lock, flags);
+
+ debug_mutex_lock_common (lock, &waiter);
+ debug_mutex_add_waiter (lock, &waiter, task_thread_info (task));
+
+ /* add waiting tasks to the end of the waitqueue (FIFO): */
+ list_add_tail (&waiter.list, &lock->wait_list);
+ waiter.task = task;
+
+ if (atomic_xchg (&lock->count, -1) == 1)
+ goto done;
+
+ lock_contended (&lock->dep_map, ip);
+
+ for (;;)
+ {
+ /*
+ * Lets try to take the lock again - this is needed even if
+ * we get here for the first time (shortly after failing to
+ * acquire the lock), to make sure that we get a wakeup once
+ * it's unlocked. Later on, if we sleep, this is the
+ * operation that gives us the lock. We xchg it to -1, so
+ * that when we release the lock, we properly wake up the
+ * other waiters:
+ */
+ if (atomic_xchg (&lock->count, -1) == 1)
+ break;
+
+ /*
+ * got a signal? (This code gets eliminated in the
+ * TASK_UNINTERRUPTIBLE case.)
+ */
+ if (unlikely (signal_pending_state (state, task)))
+ {
+ mutex_remove_waiter (lock, &waiter, task_thread_info (task));
+ mutex_release (&lock->dep_map, 1, ip);
+ spin_unlock_mutex (&lock->wait_lock, flags);
+
+ debug_mutex_free_waiter (&waiter);
+ preempt_enable ();
+ return -EINTR;
+ }
+ __set_task_state (task, state);
+
+ /* didn't get the lock, go to sleep: */
+ spin_unlock_mutex (&lock->wait_lock, flags);
+ schedule_preempt_disabled ();
+ spin_lock_mutex (&lock->wait_lock, flags);
+ }
+
+ done:
+ lock_acquired (&lock->dep_map, ip);
+ /* got the lock - rejoice! */
+ mutex_remove_waiter (lock, &waiter, current_thread_info ());
+ mutex_set_owner (lock);
+
+ /* set it to 0 if there are no waiters left: */
+ if (likely (list_empty (&lock->wait_list)))
+ atomic_set (&lock->count, 0);
+
+ spin_unlock_mutex (&lock->wait_lock, flags);
+
+ debug_mutex_free_waiter (&waiter);
+ preempt_enable ();
+
+ return 0;
+ }
+ \end{lstlisting}
+ \begin{picture}(0,0)
+ \color{red}
+ \put(7.9,28.3){\vector(-1,0){0.5}}
+ \put(8.0,28.3){\makebox(0,0)[l]{\shortstack[l]{exklusiven Zugriff\\auf Mutex sichern}}}
+ \put(7.4,2.3){\vector(-1,1){0.4}}
+ \put(7.5,2.0){\makebox(0,0)[l]{\shortstack[l]{exklusiven Zugriff auf Mutex\\wieder freigeben}}}
+ \end{picture}
+
+\end{frame}
+
+\setlength{\pdfpageheight}{40.5cm}
+
+\begin{frame}[fragile]
+
+ \lstinline{spin_lock_mutex()} -- Mutex beanspruchen, notfalls \emph{busy waiting}
+
+ Datei \file{linux-3.7-rc1/kernel/mutex.h}, ab Zeile 12
+
+ \medskip
+
+ \begin{lstlisting}
+ #define spin_lock_mutex(lock, flags) \
+ do \
+ { \
+ spin_lock (lock); \
+ (void) (flags); \
+ } \
+ while (0)
+ \end{lstlisting}
+ \begin{picture}(0,0)
+ \color{red}
+ \put(8.5,1.75){\line(-1,0){4.5}}
+ \put(8.5,1.75){\line(0,-1){2.9}}
+ \put(8.5,-1.15){\vector(-1,0){1.0}}
+ \end{picture}
+
+ \bigskip
+
+ Datei \file{linux-3.7-rc1/kernel/spinlock.h}, ab Zeile 283
+
+ \medskip
+
+ \begin{lstlisting}
+ static inline void spin_lock (spinlock_t *lock)
+ {
+ raw_spin_lock (&lock->rlock);
+ }
+ \end{lstlisting}
+ \begin{picture}(0,0)
+ \color{red}
+ \put(9.3,0.95){\line(-1,0){4.0}}
+ \put(9.3,0.95){\line(0,-1){2.1}}
+ \put(9.3,-1.15){\vector(-1,0){1.0}}
+ \end{picture}
+
+ \bigskip
+
+ Datei \file{linux-3.7-rc1/kernel/spinlock.h}, Zeile 170
+
+ \medskip
+
+ \begin{lstlisting}
+ #define raw_spin_lock(lock) _raw_spin_lock (lock)
+ \end{lstlisting}
+ \begin{picture}(0,0)
+ \color{red}
+ \put(10.0,0.55){\line(-1,0){0.5}}
+ \put(10.0,0.55){\line(0,-1){1.7}}
+ \put(10.0,-1.15){\vector(-1,0){1.3}}
+ \end{picture}
+
+ \bigskip
+
+ Datei \file{linux-3.7-rc1/include/linux/spinlock\_api\_smp.h}, Zeile 47
+
+ \medskip
+
+ \begin{lstlisting}
+ #define _raw_spin_lock(lock) __raw_spin_lock (lock)
+ \end{lstlisting}
+ \begin{picture}(0,0)
+ \color{red}
+ \put(10.7,0.55){\line(-1,0){0.5}}
+ \put(10.7,0.55){\line(0,-1){1.75}}
+ \put(10.7,-1.2){\vector(-1,0){2.3}}
+ \end{picture}
+
+ \bigskip
+
+ Datei \file{linux-3.7-rc1/kernel/spinlock.c}, ab Zeile 46 (expandiert):
+
+ \medskip
+
+ \begin{lstlisting}
+ void __lockfunc __raw_spin_lock (spinlock_t *lock)
+ {
+ for (;;)
+ {
+ preempt_disable ();
+ if (likely (do_raw_spin_trylock (lock)))
+ break;
+ preempt_enable ();
+
+ if (!(lock)->break_lock)
+ (lock)->break_lock = 1;
+ while (!raw_spin_can_lock (lock) && (lock)->break_lock)
+ arch_spin_relax (&lock->raw_lock);
+ }
+ (lock)->break_lock = 0;
+ }
+ \end{lstlisting}
+ \begin{picture}(0,0)
+ \color{red}
+ \put(10.7,4.75){\line(-1,0){3.5}}
+ \put(10.7,4.75){\line(0,-1){5.95}}
+ \put(10.7,-1.2){\vector(-1,0){1.1}}
+ \end{picture}
+
+ \bigskip
+
+ Datei \file{linux-3.7-rc1/include/linux/spinlock.h}, ab Zeile 150:
+
+ \medskip
+
+ \begin{lstlisting}
+ static inline int do_raw_spin_trylock (raw_spinlock_t *lock)
+ {
+ return arch_spin_trylock (&(lock)->raw_lock);
+ }
+ \end{lstlisting}
+ \begin{picture}(0,0)
+ \color{red}
+ \put(11.5,0.95){\line(-1,0){3.5}}
+ \put(11.5,0.95){\line(0,-1){2.1}}
+ \put(11.5,-1.15){\vector(-1,0){0.7}}
+ \end{picture}
+
+ \bigskip
+
+ Datei \file{arch/x86/include/asm/spinlock.h}, ab Zeile 116:
+
+ \medskip
+
+ \begin{lstlisting}
+ static __always_inline int arch_spin_trylock (arch_spinlock_t *lock)
+ {
+ return __ticket_spin_trylock (lock);
+ }
+ \end{lstlisting}
+ \begin{picture}(0,0)
+ \color{red}
+ \put(9.5,0.95){\line(-1,0){3.5}}
+ \put(9.5,0.95){\vector(0,-1){1.7}}
+ \end{picture}
+
+ \bigskip
+
+ Datei \file{arch/x86/include/asm/spinlock.h}, ab Zeile 65:
+
+ \medskip
+
+ \begin{lstlisting}
+ static __always_inline int __ticket_spin_trylock (arch_spinlock_t *lock)
+ {
+ arch_spinlock_t old, new;
+
+ old.tickets = ACCESS_ONCE (lock->tickets);
+ if (old.tickets.head != old.tickets.tail)
+ return 0;
+
+ new.head_tail = old.head_tail + (1 << TICKET_SHIFT);
+
+ /* cmpxchg is a full barrier, so nothing can move before it */
+ return cmpxchg (&lock->head_tail, old.head_tail, new.head_tail) == old.head_tail;
+ }
+ \end{lstlisting}
+ \begin{picture}(0,0)
+ \color{red}
+ \put(2.2,0.3){\line(0,1){0.4}}
+ \put(9.0,0.3){\line(-1,0){6.8}}
+ \put(9.0,0.3){\line(0,-1){1.45}}
+ \put(9.0,-1.15){\vector(-1,0){3.2}}
+ \end{picture}
+
+ \bigskip
+
+ Datei \file{arch/x86/include/asm/cmpxchg.h}, ab Zeile 147:
+
+ \medskip
+
+ \begin{lstlisting}
+ #define cmpxchg(ptr, old, new) \
+ __cmpxchg (ptr, old, new, sizeof (*(ptr)))
+ \end{lstlisting}
+ \begin{picture}(0,0)
+ \color{red}
+ \put(9.0,0.5){\line(-1,0){1.8}}
+ \put(9.0,0.5){\line(0,-1){1.65}}
+ \put(9.0,-1.15){\vector(-1,0){2.2}}
+ \end{picture}
+
+ \bigskip
+
+ Datei \file{arch/x86/include/asm/cmpxchg.h}, ab Zeile 131:
+
+ \medskip
+
+ \begin{lstlisting}
+ #define __cmpxchg(ptr, old, new, size) \
+ __raw_cmpxchg ((ptr), (old), (new), (size), LOCK_PREFIX)
+ \end{lstlisting}
+ \begin{picture}(0,0)
+ \color{red}
+ \put(2.2,-0.1){\line(0,1){0.3}}
+ \put(9.0,-0.1){\line(-1,0){6.8}}
+ \put(9.0,-0.1){\line(0,-1){1.05}}
+ \put(9.0,-1.15){\vector(-1,0){2.2}}
+ \end{picture}
+
+ \bigskip
+
+ Datei \file{arch/x86/include/asm/cmpxchg.h}, ab Zeile 110:
+
+ \medskip
+
+ \begin{lstlisting}
+ asm volatile (lock "cmpxchgl %2,%1" \
+ : "=a" (__ret), "+m" (*__ptr) \
+ : "r" (__new), "0" (__old) \
+ : "memory");
+ \end{lstlisting}
+ \begin{picture}(0,0)
+ \color{red}
+ \put(9.8,1.8){\vector(-1,0){0.6}}
+ \put(9.8,1.2){\line(0,1){0.6}}
+ \put(9.8,1.1){\makebox(0,0)[t]{\shortstack{atomarer und exklusiver\\Zugriff auf Spinlock\\durch Hardware-Unterstützung}}}
+ \end{picture}
+
+\end{frame}
+
+\setlength{\pdfpageheight}{\normalpdfpageheight}
+
+%\sectionnonumber{Literaturempfehlung}
+%\subsectionnonumber{Automotive Embedded Systeme}
+%
+%\begin{frame}[c]
+%
+% \showsectionnonumber
+%
+% Prof.\ Dr.\ Joachim Wietzke, FH Darmstadt,\\
+% Prof.\ Dr.\ Manh Tien Tran, FH Kaiserslautern:
+%
+% \medskip
+%
+% \showsubsectionnonumber
+%
+% \vspace{-\medskipamount}
+%
+% Springer-Verlag, Berlin, Heidelberg 2005
+%
+% \bigskip
+%
+% Lizenz: proprietär
+%
+% \medskip
+%
+% (gesetzt mit \textrm{\LaTeX}, ca.\ \EUR{10})
+%
+%\end{frame}
+
+\begin{frame}
+
+ \showsection
+ \showsubsection
+
+ Ressourcen reservieren
+ \begin{itemize}
+ \item
+ \newterm{Semaphor}\\
+ gemeinsame Variable mehrerer Prozesse\\
+ zur Regelung des Zugriffs auf eine Ressource\\[\smallskipamount]
+ Ressource belegt \textarrow\ Kontextwechsel
+ \medskip
+ \item
+ \newterm{Mutex}\\
+ Mechanismus, damit immer nur ein Prozeß gleichzeitig\\
+ auf eine Ressource zugreifen kann
+ \medskip
+ \item
+ \newterm{Spinlock} (\emph{busy waiting\/})\\
+ leichtgewichtige Alternative zu Kontextwechsel
+ \medskip
+ \item
+ \newterm{Kritischer Abschnitt -- critical section}\\
+ Programmabschnitt zwischen Reservierung\\
+ und Freigabe einer Ressource\\
+ \textarrow\ sollte immer so kurz wie möglich sein
+ \end{itemize}
+ \vspace*{-1cm}
+
+\end{frame}
+
+\begin{frame}
+
+ \showsection
+ \showsubsection
+
+ \begin{picture}(0,0)
+ \only<2-3>{\put(6.3,-7){\includegraphics[height=6cm]{philosophenproblem.jpg}}}
+ \end{picture}%
+ \newterm{Verklemmungen\/}: Gegenseitiges Blockieren von Ressourcen
+ \begin{itemize}
+ \item
+ \newterm{Deadlock\/}: Prozeß wartet
+ \item
+ \newterm{Livelock\/}: Prozeß macht andere Dinge\\
+ (z.\,B.\ \emph{busy waiting\/})
+ \end{itemize}
+
+ \pause
+ \bigskip
+
+ Beispiel: Philosophenproblem
+
+ \only<2-3>{%
+ \begin{itemize}
+ \item
+ 5 Philosophen, 5 Gabeln
+ \item
+ 2 Gabeln zum Essen notwendig
+ \item
+ Wer essen will, nimmt eine Gabel\\
+ und wartet notfalls auf die zweite.
+ \item
+ Keiner legt eine einzelne Gabel\\
+ wieder zurück.
+ \end{itemize}
+ Jeder hält 1 Gabel \textarrow\ \newterm{Verklemmung}\\[0.5\smallskipamount]
+ \pause
+ \strut\quad schweigen \textarrow\ \newterm{Deadlock}\\
+ \strut\quad philosophieren weiter \textarrow\ \newterm{Livelock}\\[-1cm]
+ }
+ \only<4->{%
+ \bigskip
+
+ Bedingungen für Verklemmungen:
+
+ \begin{minipage}[t]{4.5cm}
+ \begin{itemize}
+ \item
+ Exklusivität
+ \item
+ \newterm{hold and wait}
+ \item
+ Entzug nicht möglich
+ \item
+ zirkuläre Blockade
+ \end{itemize}
+ \end{minipage}\pause[5]
+ \begin{minipage}[t]{7.5cm}
+ \begin{itemize}
+ \arrowitem
+ Spooling
+ \arrowitem
+ simultane Zuteilung
+ \arrowitem
+ Prozesse suspendieren, beenden, \newterm{Rollback}
+ \arrowitem
+ Reihenfolge abhängig von Ressourcen
+ \end{itemize}
+ \end{minipage}
+ }
+
+\end{frame}
+
+\subsection{Prioritäten}
+
+\begin{frame}
+
+ \showsection
+ \showsubsection
+
+ Linux 0.01
+ \begin{itemize}
+ \item
+ Timer-Interrupt: Zähler des aktuellen Prozesses wird dekrementiert;\\
+ Prozeß mit höchstem Zähler bekommt Rechenzeit.
+ \item
+ Wenn es keinen laufbereiten Prozeß mit positivem Zähler gibt,\\
+ bekommen alle Prozesse gemäß ihrer \newterm{Priorität\/} neue Zähler zugewiesen.
+ \item
+ \emph{keine\/} harte Echtzeit
+ \arrowitem
+ \newterm{dynamische Prioritätenvergabe\/}:\\
+ Rechenzeit hängt vom Verhalten des Prozesses ab
+ \end{itemize}
+
+ \medskip
+
+ Echtzeitbetriebssysteme
+ \begin{itemize}
+ \item
+ Prozesse können einen festen Anteil an Rechenzeit bekommen.
+ \item
+ Bei Ereignissen können Prozesse hoher Priorität\\
+ Prozesse niedriger Priorität unterbrechen, aber nicht umgekehrt.
+ \arrowitem
+ \newterm{statische Prioritätenvergabe}
+ \end{itemize}
+
+\end{frame}
+
+\begin{frame}
+
+ \showsection
+ \showsubsection
+
+ Echtzeitbetriebssysteme
+ \begin{itemize}
+ \item
+ Prozesse können einen festen Anteil an Rechenzeit bekommen.
+ \item
+ Bei Ereignissen können Prozesse hoher Priorität\\
+ Prozesse niedriger Priorität unterbrechen, aber nicht umgekehrt.
+ \end{itemize}
+
+ \vspace{0cm plus 1filll}
+
+ \begin{center}
+ \begin{picture}(11,4)(-1,0)
+ \small
+
+ \put(-0.1,0.5){\vector(1,0){10.1}}
+ \put(9.75,0.4){\makebox(0,0)[tr]{Zeit}}
+ \put(0,0.4){\vector(0,1){3.6}}
+ \put(-0.1,3.75){\makebox(0,0)[tr]{Priorität}}
+
+ \put(1,3){{\color{lightorange}\rule{0.5cm}{0.4cm}}}
+ \put(3,3){{\color{lightorange}\rule{0.7cm}{0.4cm}}}
+ \put(5,3){{\color{lightorange}\rule{0.6cm}{0.4cm}}}
+ \put(7,3){{\color{lightorange}\rule{0.5cm}{0.4cm}}}
+ \put(9,3){{\color{lightorange}\rule{0.7cm}{0.4cm}}}
+ \put(0,3){\line(1,0){10}}
+
+ \put(0,1){{\color{lightgreen}\rule{1cm}{0.4cm}}}
+ \put(1.5,1){{\color{lightgreen}\rule{1.5cm}{0.4cm}}}
+ \put(3.7,1){{\color{lightgreen}\rule{0.6cm}{0.4cm}}}
+ \alt<1>{%
+ \put(7.9,1){{\color{lightgreen}\rule{1.1cm}{0.4cm}}}
+ }{%
+ \put(8.1,1){{\color{lightgreen}\rule{0.9cm}{0.4cm}}}
+ }
+ \put(9.7,1){{\color{lightgreen}\rule{0.3cm}{0.4cm}}}
+ \put(0,1){\line(1,0){10}}
+
+ \pause
+
+ \put(4.6,2){{\color{lightyellow}\rule{0.4cm}{0.4cm}}}
+ \put(5.7,2){{\color{lightyellow}\rule{1.3cm}{0.4cm}}}
+ \put(7.7,2){{\color{lightyellow}\rule{0.4cm}{0.4cm}}}
+ \put(0,2){\line(1,0){10}}
+
+ \end{picture}
+ \end{center}
+
+\end{frame}
+
+\subsectionnonumber{Prioritäten \protect\color{darkgray}und Ressourcen}
+
+\begin{frame}
+
+ \showsection
+ \showsubsection
+
+ \only<4->{%
+ Der höher priorisierte Prozeß bewirkt selbst,\\
+ daß er eine Ressource verspätet bekommt.
+
+ \medskip
+
+ \textarrow\ \newterm{begrenzte Prioritätsinversion}
+
+ \medskip
+
+ maximale Verzögerung: Länge des kritischen Bereichs
+ }
+
+ \vspace{0cm plus 1filll}
+
+ \begin{center}
+ \begin{picture}(11,4)(-1,0)
+ \small
+
+ \put(-0.1,0.5){\vector(1,0){10.1}}
+ \put(9.75,0.4){\makebox(0,0)[tr]{Zeit}}
+ \put(0,0.4){\vector(0,1){3.6}}
+ \put(-0.1,3.75){\makebox(0,0)[tr]{Priorität}}
+
+ \put(1,3){{\color{lightorange}\rule{0.5cm}{0.4cm}}}
+ \only<1-2>{\put(3,3){{\color{lightorange}\rule{0.7cm}{0.4cm}}}}
+ \only<3->{\put(3,3){{\color{lightorange}\rule{0.4cm}{0.4cm}}}}
+ \only<3-4>{%
+ \put(3.4,3){{\color{red}\rule{0.8cm}{0.4cm}}}
+ \put(4.2,3){{\color{lightorange}\rule{0.2cm}{0.4cm}}}
+ {\thicklines
+ \put(3.3,2.95){\line(2,1){1.0}}
+ \put(3.3,3.45){\line(2,-1){1.0}}}
+ }
+ \only<5->{%
+ \put(3.9,3){{\color{red}\rule{0.8cm}{0.4cm}}}
+ \put(4.7,3){{\color{lightorange}\rule{0.2cm}{0.4cm}}}
+ }
+ \put(5,3){{\color{lightorange}\rule{0.6cm}{0.4cm}}}
+ \only<1-2>{%
+ \put(5.4,3){{\color{red}\rule{0.8cm}{0.4cm}}}
+ \put(6.2,3){{\color{lightorange}\rule{0.2cm}{0.4cm}}}
+ }
+ \put(7,3){{\color{lightorange}\rule{0.5cm}{0.4cm}}}
+ \put(9,3){{\color{lightorange}\rule{0.7cm}{0.4cm}}}
+ \put(0,3){\line(1,0){10}}
+
+ \only<2->{%
+ \put(0,1){{\color{lightgreen}\rule{1cm}{0.4cm}}}
+ \put(1.5,1){{\color{lightgreen}\rule{1.5cm}{0.4cm}}}
+ \put(2.6,1){{\color{medgreen}\rule{0.4cm}{0.4cm}}}
+ \only<2-4>{%
+ \put(3.7,1){{\color{medgreen}\rule{0.5cm}{0.4cm}}}
+ \put(4.2,1){{\color{lightgreen}\rule{0.3cm}{0.4cm}}}
+ }
+ \only<5->{%
+ \put(3.4,1){{\color{medgreen}\rule{0.5cm}{0.4cm}}}
+ \put(4.9,1){{\color{lightgreen}\rule{0.1cm}{0.4cm}}}
+ \put(5.6,1){{\color{lightgreen}\rule{0.2cm}{0.4cm}}}
+ }
+ \put(7.7,1){{\color{lightgreen}\rule{1.3cm}{0.4cm}}}
+ \put(9.7,1){{\color{lightgreen}\rule{0.3cm}{0.4cm}}}
+ \put(0,1){\line(1,0){10}}
+ }
+ \end{picture}
+ \end{center}
+
+\end{frame}
+
+\begin{frame}
+
+ \showsection
+ \showsubsection
+
+ \visible<4->{%
+ Ein Prozeß mit mittlerer Priorität bewirkt,
+ daß ein Prozeß mit hoher Priorität eine Ressource überhaupt nicht bekommt.
+
+ \medskip
+
+ \textarrow\ }\newterm{unbegrenzte Prioritätsinversion}
+
+ \pause
+ \vspace{0cm plus 1filll}
+
+ \begin{center}
+ \begin{picture}(11,4)(-1,0)
+ \small
+
+ \put(-0.1,0.5){\vector(1,0){10.1}}
+ \put(9.75,0.4){\makebox(0,0)[tr]{Zeit}}
+ \put(0,0.4){\vector(0,1){3.6}}
+ \put(-0.1,3.75){\makebox(0,0)[tr]{Priorität}}
+
+ \put(1,3){{\color{lightorange}\rule{0.5cm}{0.4cm}}}
+ \put(3,3){{\color{lightorange}\rule{0.4cm}{0.4cm}}}
+ \only<2>{%
+ \put(3.4,3){{\color{red}\rule{0.8cm}{0.4cm}}}
+ \put(4.2,3){{\color{lightorange}\rule{0.2cm}{0.4cm}}}
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+ \put(7,3){{\color{lightorange}\rule{0.5cm}{0.4cm}}}
+ \put(9,3){{\color{lightorange}\rule{0.7cm}{0.4cm}}}
+ }
+ \put(0,3){\line(1,0){10}}
+
+ \only<2->{%
+ \put(0,1){{\color{lightgreen}\rule{1cm}{0.4cm}}}
+ \put(1.5,1){{\color{lightgreen}\rule{1.1cm}{0.4cm}}}
+ \alt<1-4>{%
+ \put(2.6,1){{\color{medgreen}\rule{0.4cm}{0.4cm}}}
+ }{%
+ \put(2.6,1){{\color{medgreen}\rule{0.2cm}{0.4cm}}}
+ }
+ \only<2>{%
+ \put(3.7,1){{\color{medgreen}\rule{0.5cm}{0.4cm}}}
+ \put(4.2,1){{\color{lightgreen}\rule{0.3cm}{0.4cm}}}
+ }
+ \only<3-4>{%
+ \put(3.4,1){{\color{medgreen}\rule{0.5cm}{0.4cm}}}
+% \put(3.9,1){{\color{lightgreen}\rule{0.3cm}{0.4cm}}}
+ }
+ \only<2>{%
+ \put(7.7,1){{\color{lightgreen}\rule{1.3cm}{0.4cm}}}
+ \put(9.7,1){{\color{lightgreen}\rule{0.3cm}{0.4cm}}}
+ }
+ \put(0,1){\line(1,0){10}}
+ }
+
+ \only<5->{%
+ \put(2.8,2){{\color{lightyellow}\rule{0.2cm}{0.4cm}}}
+ \put(3.4,2){{\color{lightyellow}\rule{6.6cm}{0.4cm}}}
+ \put(0,2){\line(1,0){10}}
+ }
+ \end{picture}
+ \end{center}
+
+\end{frame}
+
+\begin{frame}
+
+ \showsection
+ \showsubsection
+
+ Ein Prozeß mit mittlerer Priorität bewirkt,
+ daß ein Prozeß mit hoher Priorität eine Ressource überhaupt nicht bekommt.
+
+ \medskip
+
+ \textarrow\ \newterm{unbegrenzte Prioritätsinversion}
+
+ \medskip
+
+ Beispiel: Beinahe-Verlust der Marssonde \emph{Pathfinder\/} im Juli 1997
+
+ \only<1>{%
+ \begin{center}
+ \includegraphics[width=8.7cm]{pathfinder.jpg}
+ \vspace*{-1.5cm}
+ \end{center}
+ }
+
+ \bigskip
+
+ \only<2>{%
+ Gegenmaßnahmen
+ \begin{itemize}
+ \item
+ \newterm{Priority Inheritance -- Prioritätsvererbung}\\
+ Der Besitzer des Mutex erbt die Priorität\\
+ des Prozesses, der auf den Mutex wartet.
+ \end{itemize}
+
+ \bigskip
+
+ \begin{minipage}{7.0cm}
+ \begin{flushright}
+ \url{http://research.microsoft.com/en-us/\\um/people/mbj/Mars\_Pathfinder/}
+ \end{flushright}
+ \end{minipage}
+
+ \vspace{1.35cm}\strut\hfill\makebox(0,0)[br]{\includegraphics[height=2.8cm]{pathfinder.jpg}}\vspace*{-1cm}
+ }
+
+\end{frame}
+
+\begin{frame}
+
+ \showsection
+ \showsubsection
+
+ Ein Prozeß mit mittlerer Priorität bewirkt,
+ daß ein Prozeß mit hoher Priorität eine Ressource überhaupt nicht bekommt.
+
+ \medskip
+
+ \textarrow\ \newterm{unbegrenzte Prioritätsinversion}
+
+ \bigskip
+
+ Gegenmaßnahme: \newterm{Priority Inheritance -- Prioritätsvererbung}
+
+ \vspace{0cm plus 1filll}
+
+ \begin{center}
+ \begin{picture}(11,4)(-1,0)
+ \small
+
+ \put(-0.1,0.5){\vector(1,0){10.1}}
+ \put(9.75,0.4){\makebox(0,0)[tr]{Zeit}}
+ \put(0,0.4){\vector(0,1){3.6}}
+ \put(-0.1,3.75){\makebox(0,0)[tr]{Priorität}}
+
+ \put(0,1){{\color{lightgreen}\rule{1cm}{0.4cm}}}
+ \put(1.5,1){{\color{lightgreen}\rule{1.1cm}{0.4cm}}}
+ \put(2.6,1){{\color{medgreen}\rule{0.2cm}{0.4cm}}}
+ \put(0,1){\line(1,0){10}}
+
+ \put(2.8,2){{\color{lightyellow}\rule{0.2cm}{0.4cm}}}
+ \only<1-2>{%
+ \put(3.4,2){{\color{lightyellow}\rule{6.6cm}{0.4cm}}}
+ }
+ \put(0,2){\line(1,0){10}}
+
+ \put(1,3){{\color{lightorange}\rule{0.5cm}{0.4cm}}}
+ \put(3,3){{\color{lightorange}\rule{0.4cm}{0.4cm}}}
+ \put(0,3){\line(1,0){10}}
+
+ \only<2>{%
+ \put(3.4,3){{\color{red}\rule{0.8cm}{0.4cm}}}
+ {\thicklines
+ \put(3.3,2.95){\line(2,1){1.0}}
+ \put(3.3,3.45){\line(2,-1){1.0}}}
+ }
+
+ \only<3->{%
+ \put(3.4,3){{\color{medgreen}\rule{0.7cm}{0.4cm}}}
+ \put(4.1,3){{\color{red}\rule{0.8cm}{0.4cm}}}
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+ \put(7,3){{\color{lightorange}\rule{0.5cm}{0.4cm}}}
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+ \put(9,3){{\color{lightorange}\rule{0.7cm}{0.4cm}}}
+ \put(9.7,2){{\color{lightyellow}\rule{0.3cm}{0.4cm}}}
+ }
+ \end{picture}
+ \end{center}
+
+\end{frame}
+
+\begin{frame}
+
+ \showsection
+ \showsubsection
+
+ Ein Prozeß mit mittlerer Priorität bewirkt,
+ daß ein Prozeß mit hoher Priorität eine Ressource überhaupt nicht bekommt.
+
+ \medskip
+
+ \textarrow\ \newterm{unbegrenzte Prioritätsinversion}
+
+ \bigskip
+
+ Gegenmaßnahme: \newterm{Priority Ceiling -- Prioritätsobergrenze}
+
+ \vspace{0cm plus 1filll}
+
+ \begin{center}
+ \begin{picture}(11,4)(-1,0)
+ \small
+
+ \put(-0.1,0.5){\vector(1,0){10.1}}
+ \put(9.75,0.4){\makebox(0,0)[tr]{Zeit}}
+ \put(0,0.4){\vector(0,1){3.6}}
+ \put(-0.1,3.75){\makebox(0,0)[tr]{Priorität}}
+
+ \put(0,1){{\color{lightgreen}\rule{1cm}{0.4cm}}}
+ \put(1.5,1){{\color{lightgreen}\rule{1.1cm}{0.4cm}}}
+% \only<1>{%
+% \put(2.6,1){{\color{medgreen}\rule{0.2cm}{0.4cm}}}
+% }
+ \put(0,1){\line(1,0){10}}
+
+% \only<1>{%
+% \put(2.8,2){{\color{lightyellow}\rule{0.2cm}{0.4cm}}}
+% \put(3.4,2){{\color{lightyellow}\rule{6.6cm}{0.4cm}}}
+% }
+ \put(0,2){\line(1,0){10}}
+
+ \put(1,3){{\color{lightorange}\rule{0.5cm}{0.4cm}}}
+% \only<1>{%
+% \put(3,3){{\color{lightorange}\rule{0.4cm}{0.4cm}}}
+% }
+ \put(0,3){\line(1,0){10}}
+
+% \only<2>{%
+% \only<2>{%
+ \put(2.6,3){{\color{medgreen}\rule{0.9cm}{0.4cm}}}
+ \put(3.5,3){{\color{lightorange}\rule{0.4cm}{0.4cm}}}
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+ \put(9.7,2){{\color{lightyellow}\rule{0.3cm}{0.4cm}}}
+% }
+ \end{picture}
+ \end{center}
+
+\end{frame}
+
+\begin{frame}
+
+ \showsection
+ \showsubsection
+
+ Ein Prozeß mit mittlerer Priorität bewirkt,
+ daß ein Prozeß mit hoher Priorität eine Ressource überhaupt nicht bekommt.
+
+ \medskip
+
+ \textarrow\ \newterm{unbegrenzte Prioritätsinversion}
+
+ \medskip
+
+ Beispiel: Beinahe-Verlust der Marssonde \emph{Pathfinder\/} im Juli 1997
+
+ \bigskip
+
+ Gegenmaßnahmen
+ \begin{itemize}
+ \item
+ \newterm{Priority Inheritance -- Prioritätsvererbung}\\
+ Der Besitzer des Mutex erbt die Priorität\\
+ des Prozesses, der auf den Mutex wartet.
+ \smallskip
+ \item
+ \newterm{Priority Ceiling -- Prioritätsobergrenze}\\
+ Der Besitzer des Mutex bekommt sofort\\
+ die Priorität des höchstmöglichen Prozesses,\\
+ der evtl.\ den Mutex benötigen könnte.
+ \pause
+ \begin{picture}(0,0)
+ \put(1.2,1.45){\makebox(0,0)[l]{$\left\}\rule{0pt}{1.7cm}\right.$
+ \begin{minipage}{4cm}
+ nur möglich, wenn\\
+ Mutexe im Spiel sind
+ \end{minipage}}}
+ \end{picture}
+ \smallskip
+ \pause
+ \item
+ \newterm{Priority Aging}\\
+ Die Priorität wächst mit der Wartezeit.
+ \end{itemize}
+ \vspace*{-1cm}
+
+\end{frame}
+
+\subsection{Echtzeitbetriebssysteme}
+
+\begin{frame}
+
+ \showsection
+ \showsubsection
+
+ Wikipedia:
+ \begin{quote}
+ Ein \newterm{Echtzeitbetriebssystem\/} (englisch \newterm{real-time operating system},\\
+ kurz \newterm{RTOS\/} genannt) ist ein Betriebssystem mit zusätzlichen Echtzeit-Funktionen
+ für die unbedingte Einhaltung von Zeitbedingungen
+ und die Vorhersagbarkeit des Prozessverhaltens (hartes Echtzeitverhalten).
+ \end{quote}
+
+ \pause
+ \vspace{-0.5cm}
+ \begin{displaymath}
+ \text{Echtzeitbetriebssystem}
+ ~=~ \text{Betriebssystem}
+ ~+~ \left(\begin{array}{c}
+ \text{Semaphoren} \\
+ \text{Mutexe} \\
+ \text{Spinlocks} \\
+ \text{Prioritätsvererbung} \\
+ \text{Prioritätsobergrenze} \\
+ \text{Prioritätsalterung}
+ \end{array}\right)
+ \end{displaymath}
+
+\end{frame}
+
+\begin{frame}
+
+ \showsection
+ \showsubsection
+
+ Beispiele
+
+ \renewcommand{\arraystretch}{1.2}
+
+ \begin{center}
+ \begin{tabular}{|l|l|l|l|}\hline
+ Name & Lizenz & kompatibel zu & Besonderheiten \\\hline\hline
+ TinyOS & BSD & -- & kooperativ, eigene Sprache \\\hline
+ FreeRTOS & GPL & -- & \\\hline
+ MicroC/OS-II & prop. & -- & mehrfach zertifiziert \\\hline
+ eCos & GPL & Unix & stark konfigurierbar \\\hline
+ QNX & prop. & Unix & im Automobilbereich beliebt \\\hline
+ VxWorks & prop. & Unix & mehrfach zertifiziert \\\hline
+ RTAI & GPL & Unix (Linux) & Linux als Hintergrundprozeß \\\hline
+ RT\_PREEMPT & GPL & Unix (Linux) & angepaßter Kernel \\\hline
+ Xenomai & GPL & Unix (Linux) & Dual-Kernel \\\hline
+ Windows CE / Em- & & & \\[-3pt]
+ bedded Compact & prop. & MS-Windows & \\\hline
+ \end{tabular}
+ \end{center}
+ \vspace*{-1cm}
+
+\end{frame}
+
+\nosectionnonumber{Vertiefung Systemtechnik -- Eingebettete Systeme}
+
+\begin{frame}
+
+ \shownosectionnonumber
+
+ \begin{itemize}
+ \item[\textbf{1}] \textbf{Einführung}
+ \hfill\makebox(0,0)[br]{\raisebox{2.25ex}{\url{https://gitlab.cvh-server.de/pgerwinski/es.git}}}%
+ \item[\textbf{2}] \textbf{Einführung in Unix}
+ \item[\textbf{3}] \textbf{TCP/IP in der Praxis}
+ \item[\textbf{4}] \textbf{Bus-Systeme}
+ \item[\textbf{5}] \textbf{Echtzeit}
+ \begin{itemize}
+ \item[5.1] Was ist Echtzeit?
+ \item[5.2] Echtzeitprogrammierung
+ \item[5.3] Multitasking
+ \item[5.4] Ressourcen
+ \item[5.5] Prioritäten
+ \color{medgreen}
+ \item[5.6] Echtzeitbetriebssysteme
+ \end{itemize}
+ \item[\textbf{6}] \textbf{Web-Interfaces}
+ \begin{itemize}
+ \color{red}
+ \item[6.1] HTTP, HTML und CGI
+ \item[6.2] Externe CGI-Skripte, GET und POST
+ \item[6.3] Skript im Server: PHP
+ \item[6.4] Server im Skript: Twisted
+ \end{itemize}
+ \vspace*{-\smallskipamount}
+ \item[\textbf{\dots}]
+ \underconstruction
+ \end{itemize}
+
+\end{frame}
+
+\section{Web-Interfaces}
+\subsection{HTTP, HTML und CGI}
+
+\begin{frame}[fragile]
+ \showsection
+ \showsubsection
+
+ \begin{lstlisting}[style=terminal]
+ $ ¡nc -C localhost 80¿
+ GET / HTTP/1.1
+ Host: localhost
+
+ HTTP/1.1 200 OK
+ Date: Wed, 22 Nov 2017 19:58:55 GMT
+ Server: Apache/2.4.25 (Debian)
+ [...]
+ Content-Type: text/html
+
+ <html>
+ <body>
+ <h1 align="center">Vertiefung<br>Vertiefung Systemtechnik – Eingebettete Systeme</h1>
+ <p align="center">23. November 2017</p>
+ <p align="center">Prof. Dr. Peter Gerwinski</p>
+ </body>
+ </html>
+ \end{lstlisting}
+ \vspace*{-1cm}
+\end{frame}
+
+\begin{frame}[fragile]
+ \showsection
+ \showsubsection
+
+ \begin{itemize}
+ \item
+ \newterm{Hypertext Transport Protocol (HTTP)}: Netzwerk-Protokoll\\
+ HTML-Inhalt + zusätzliche Daten
+ \pause
+ \item
+ \newterm{Hypertext Markup Language (HTML)}: Markup-Sprache\\
+ Inhalte + Formulare
+ \begin{onlyenv}<2>
+ \bigskip
+ \begin{lstlisting}[language=html,gobble=10]
+ <form action="/cgi-bin/welcome.cgi" method="get">
+ Your name: <input type="text" name="name"><br>
+ <input type="submit">
+ </form>
+ \end{lstlisting}
+ \vspace*{-2cm}
+ \end{onlyenv}
+ \pause
+ \item
+ \newterm{Common Gateway Interface (CGI)}: Schnittstelle zu Programmen\\
+ Liste von Variablen mit Werten
+ \par\smallskip
+ \begin{itemize}
+ \item
+ \newterm{GET-Methode}: Umgebungsvariable \lstinline{QUERY_STRING}
+ \smallskip
+ \item
+ \newterm{POST-Methode}: Standardeingabe
+ \end{itemize}
+ \end{itemize}
+ \bigskip
+ \lstinline[style=terminal]{http://localhost/cgi-bin/welcome.cgi?name=Peter&answer=42}
+\end{frame}
+
+\subsection{Externe CGI-Skripte, GET und POST}
+
+\begin{frame}[fragile]
+ \showsection
+ \showsubsection
+
+ \begin{itemize}\itemsep\medskipamount
+ \item
+ HTML-Formular verweist auf CGI-Programm ("`CGI-Skript"')
+ \par
+ \lstinline[language=html]{<form action="/cgi-bin/welcome.cgi"}
+ \lstinline[language=html]{method="get">}
+ \item
+ Web-Server ruft CGI-Programm auf
+ \item
+ CGI-Programm wertet Variablenliste aus
+ \begin{itemize}
+ \item
+ GET-Methode: Umgebungsvariable \lstinline{QUERY_STRING}
+ \smallskip
+ \item
+ POST-Methode: Standardeingabe
+ \end{itemize}
+ \item
+ CGI-Programm gibt HTTP-Header und Inhalt aus
+ \par\smallskip
+ \begin{lstlisting}[language=bash]
+ #!/bin/bash
+ echo Content-Type: text/plain
+ echo
+ echo "Hello, world!"
+ \end{lstlisting}
+ \item
+ speziell: Inhalt ist \lstinline{text/html}
+ \end{itemize}
+\end{frame}
+
+\subsection{Skript im Server: PHP}
+
+\begin{frame}[fragile]
+ \showsection
+ \showsubsection
+
+ \begin{itemize}
+ \item
+ Interpreter in Web-Server integriert
+ \end{itemize}
+
+ \bigskip
+
+ \begin{lstlisting}[language=php]
+ <html>
+ <body>
+ Hello, <?php echo $_POST["name"]; ?>!
+ </body>
+ </html>
+ \end{lstlisting}
+\end{frame}
+
+\subsection{Server im Skript: Twisted}
+
+\begin{frame}[fragile]
+ \showsection
+ \showsubsection
+
+ \begin{itemize}
+ \item
+ individuell geschriebener Web-Server
+ \item
+ "`Baukasten"' in JavaScript: \file{node.js}
+ \item
+ "`Baukasten"' in Python: \file{Twisted}
+ \end{itemize}
+
+ \bigskip
+
+ \begin{lstlisting}[language=python]
+ def render_GET(self, request):
+ return '<html><body><form method="POST">Your name: ' \
+ + '<input name="name" type="text" /><br/>' \
+ + '<input type="submit"></form></body></html>'
+
+ def render_POST(self, request):
+ return '<html><body>Hello, %s!</body></html>' \
+ % (cgi.escape(request.args["name"][0]),)
+ \end{lstlisting}
+\end{frame}
+
+\nosectionnonumber{Vertiefung Systemtechnik -- Eingebettete Systeme}
+
+\begin{frame}
+
+ \shownosectionnonumber
+
+ \begin{itemize}
+ \item[\textbf{1}] \textbf{Einführung}
+ \hfill\makebox(0,0)[br]{\raisebox{2.25ex}{\url{https://gitlab.cvh-server.de/pgerwinski/es.git}}}%
+ \item[\textbf{2}] \textbf{Einführung in Unix}
+ \item[\textbf{3}] \textbf{TCP/IP in der Praxis}
+ \item[\textbf{4}] \textbf{Bus-Systeme}
+ \item[\textbf{5}] \textbf{Echtzeit}
+ \begin{itemize}
+ \item[5.1] Was ist Echtzeit?
+ \item[5.2] Echtzeitprogrammierung
+ \item[5.3] Multitasking
+ \item[5.4] Ressourcen
+ \item[5.5] Prioritäten
+ \color{medgreen}
+ \item[5.6] Echtzeitbetriebssysteme
+ \end{itemize}
+ \item[\textbf{6}] \textbf{Web-Interfaces}
+ \begin{itemize}
+ \color{medgreen}
+ \item[6.1] HTTP, HTML und CGI
+ \item[6.2] Externe CGI-Skripte, GET und POST
+ \item[6.3] Skript im Server: PHP
+ \item[6.4] Server im Skript: Twisted
+ \end{itemize}
+ \vspace*{-\smallskipamount}
+ \item[\textbf{\dots}]
+ \underconstruction
+ \end{itemize}
+
+\end{frame}
+
+\end{document}
diff --git a/20171123/filepos-1.c b/20171123/filepos-1.c
new file mode 100644
index 0000000000000000000000000000000000000000..d4525c84a17e0c5e9cdedca31c8368a0581e139d
--- /dev/null
+++ b/20171123/filepos-1.c
@@ -0,0 +1,11 @@
+#include <stdio.h>
+
+int main (void)
+{
+ FILE *f = fopen ("filepos-1.txt", "w+");
+ fprintf (f, "Hello, world!\n");
+ char buffer[100] = "";
+ fgets (buffer, sizeof (buffer), f);
+ printf ("buffer = \"%s\"\n", buffer);
+ return 0;
+}
diff --git a/20171123/filepos-1.txt b/20171123/filepos-1.txt
new file mode 100644
index 0000000000000000000000000000000000000000..af5626b4a114abcb82d63db7c8082c3c4756e51b
--- /dev/null
+++ b/20171123/filepos-1.txt
@@ -0,0 +1 @@
+Hello, world!
diff --git a/20171123/filepos-2.c b/20171123/filepos-2.c
new file mode 100644
index 0000000000000000000000000000000000000000..c0af4d972d2c5ca4057952dae9f749e430aa560e
--- /dev/null
+++ b/20171123/filepos-2.c
@@ -0,0 +1,12 @@
+#include <stdio.h>
+
+int main (void)
+{
+ FILE *f = fopen ("filepos-1.txt", "w+");
+ fprintf (f, "Hello, world!\n");
+ char buffer[100] = "";
+ fseek (f, 0, SEEK_SET);
+ fgets (buffer, sizeof (buffer), f);
+ printf ("buffer = \"%s\"\n", buffer);
+ return 0;
+}
diff --git a/20171123/grep-find-1.log b/20171123/grep-find-1.log
new file mode 100644
index 0000000000000000000000000000000000000000..f45a33b08af556c7d972748594d7677d90fa0111
--- /dev/null
+++ b/20171123/grep-find-1.log
@@ -0,0 +1,9 @@
+$ grep "Hello" $(find . -type f -name "*.[ch]")
+
+Falls Argument-Liste zu lang wird:
+
+$ find . -type f -name "*.[ch]" -exec grep "Hello" {} +
+
+Das "{}" steht für die von "find" gefundene Datei.
+"+" bedeutet, daß "find" das Programm "grep" auch für mehrere gefundene Dateien aufruft.
+Mit "\;" statt "+" wird "grep" für jede Datei einzeln aufgerufen.
diff --git a/20171123/herzschrittmacher.jpg b/20171123/herzschrittmacher.jpg
new file mode 120000
index 0000000000000000000000000000000000000000..92d8f0053003cc555aec83f5d088f1cec822ad81
--- /dev/null
+++ b/20171123/herzschrittmacher.jpg
@@ -0,0 +1 @@
+../common/herzschrittmacher.jpg
\ No newline at end of file
diff --git a/20171123/logo-hochschule-bochum-cvh-text.pdf b/20171123/logo-hochschule-bochum-cvh-text.pdf
new file mode 120000
index 0000000000000000000000000000000000000000..a05946126bc0ce6a2818740da2893f59eb0c659c
--- /dev/null
+++ b/20171123/logo-hochschule-bochum-cvh-text.pdf
@@ -0,0 +1 @@
+../common/logo-hochschule-bochum-cvh-text.pdf
\ No newline at end of file
diff --git a/20171123/logo-hochschule-bochum.pdf b/20171123/logo-hochschule-bochum.pdf
new file mode 120000
index 0000000000000000000000000000000000000000..b6b9491e370e499c9276918182cdb82cb311bcd1
--- /dev/null
+++ b/20171123/logo-hochschule-bochum.pdf
@@ -0,0 +1 @@
+../common/logo-hochschule-bochum.pdf
\ No newline at end of file
diff --git a/20171123/pathfinder.jpg b/20171123/pathfinder.jpg
new file mode 120000
index 0000000000000000000000000000000000000000..23c6444fee26e0cf0dd2f8639484b00aa5021b59
--- /dev/null
+++ b/20171123/pathfinder.jpg
@@ -0,0 +1 @@
+../common/pathfinder.jpg
\ No newline at end of file
diff --git a/20171123/pgslides.sty b/20171123/pgslides.sty
new file mode 120000
index 0000000000000000000000000000000000000000..5be1416f4216f076aa268901f52a15d775e43f64
--- /dev/null
+++ b/20171123/pgslides.sty
@@ -0,0 +1 @@
+../common/pgslides.sty
\ No newline at end of file
diff --git a/20171123/philosophenproblem.jpg b/20171123/philosophenproblem.jpg
new file mode 120000
index 0000000000000000000000000000000000000000..26591b2ac2dddfd4786814baf3f19ecb67f1f5ee
--- /dev/null
+++ b/20171123/philosophenproblem.jpg
@@ -0,0 +1 @@
+../common/philosophenproblem.jpg
\ No newline at end of file
diff --git a/20171123/photo-20171116-152713.jpg b/20171123/photo-20171116-152713.jpg
new file mode 100644
index 0000000000000000000000000000000000000000..5dcca28aba3dab5d07c1e6e638ed696ed05f03e2
Binary files /dev/null and b/20171123/photo-20171116-152713.jpg differ
diff --git a/20171123/quadrocopter.jpg b/20171123/quadrocopter.jpg
new file mode 120000
index 0000000000000000000000000000000000000000..7eaf0c024b63b7bc1dd3df2c17c8ab93f67fc15c
--- /dev/null
+++ b/20171123/quadrocopter.jpg
@@ -0,0 +1 @@
+../common/quadrocopter.jpg
\ No newline at end of file
diff --git a/20171123/rp6.jpg b/20171123/rp6.jpg
new file mode 120000
index 0000000000000000000000000000000000000000..2a0ecff23845770c3a98178eca6dce3ec73aca58
--- /dev/null
+++ b/20171123/rp6.jpg
@@ -0,0 +1 @@
+../common/rp6.jpg
\ No newline at end of file
diff --git a/20171123/sed-screenshot-1.log b/20171123/sed-screenshot-1.log
new file mode 100644
index 0000000000000000000000000000000000000000..2dfce306c155d042bfc5735ae0f0a7528a415006
--- /dev/null
+++ b/20171123/sed-screenshot-1.log
@@ -0,0 +1,26 @@
+cassini/usr/lib/cgi-bin> QUERY_STRING="name=Peter&answer=42"
+cassini/usr/lib/cgi-bin> echo $QUERY_STRING
+name=Peter&answer=42
+cassini/usr/lib/cgi-bin> echo $QUERY_STRING | sed -e 's/=/FISCH/'
+nameFISCHPeter&answer=42
+cassini/usr/lib/cgi-bin> echo $QUERY_STRING | sed -e 's/=/FISCH/g'
+nameFISCHPeter&answerFISCH42
+cassini/usr/lib/cgi-bin> echo $QUERY_STRING | sed -e 's/[=&]/FISCH/g'
+nameFISCHPeterFISCHanswerFISCH42
+cassini/usr/lib/cgi-bin> echo $QUERY_STRING | sed -e 's/[^=&]/X/g'
+XXXX=XXXXX&XXXXXX=XX
+cassini/usr/lib/cgi-bin> echo $QUERY_STRING | sed -e 's/^[^=&]/X/g'
+Xame=Peter&answer=42
+cassini/usr/lib/cgi-bin> echo $QUERY_STRING | sed -e 's/[^=&]$/X/g'
+name=Peter&answer=4X
+cassini/usr/lib/cgi-bin> echo $QUERY_STRING | sed -e '\<s/[^=&]\>/X/g'
+sed: -e Ausdruck #1, Zeichen 15: Nicht beendeter regulärer Adressausdruck
+cassini/usr/lib/cgi-bin> echo $QUERY_STRING | sed -e 's/\<[^=&]\>/X/g'
+name=Peter&answer=42
+cassini/usr/lib/cgi-bin> echo $QUERY_STRING | sed -e 's/\<[^=&]/X/g'
+Xame=Xeter&Xnswer=X2
+cassini/usr/lib/cgi-bin> echo $QUERY_STRING | sed -e 's/[^=&]\>/X/g'
+namX=PeteX&answeX=4X
+cassini/usr/lib/cgi-bin> echo $QUERY_STRING | sed -e 's/\([^=&]\)/X\1/g'
+XnXaXmXe=XPXeXtXeXr&XaXnXsXwXeXr=X4X2
+cassini/usr/lib/cgi-bin>
diff --git a/20171123/templates-1.c b/20171123/templates-1.c
new file mode 100644
index 0000000000000000000000000000000000000000..07f1c2097247baf3db831ff8ecff8a52e0c78024
--- /dev/null
+++ b/20171123/templates-1.c
@@ -0,0 +1,17 @@
+#include <stdio.h>
+
+#define PRINT_FUNC(name, type, spec) \
+ void print_##name (type x) \
+ { \
+ printf (spec "\n", x); \
+ }
+
+PRINT_FUNC (int, int, "%d")
+PRINT_FUNC (string, char *, "%s")
+
+int main (void)
+{
+ print_string ("Hello, world!");
+ print_int (42);
+ return 0;
+}
diff --git a/20171123/twisted-get.py b/20171123/twisted-get.py
new file mode 100755
index 0000000000000000000000000000000000000000..0c9e3d61b999cb542b9094f81ba79a7067888e4b
--- /dev/null
+++ b/20171123/twisted-get.py
@@ -0,0 +1,26 @@
+#!/usr/bin/python2
+
+from twisted.web.server import Site
+from twisted.web.resource import Resource
+from twisted.internet import reactor, endpoints
+
+import cgi
+
+class FormPage(Resource):
+ def render_GET(self, request):
+ return '<html><body><form action="/welcome" method="GET">Your name: ' \
+ + '<input name="name" type="text" /><br/>' \
+ + '<input type="submit"></form></body></html>'
+
+class WelcomePage(Resource):
+ def render_GET(self, request):
+ return '<html><body>Hello, %s!<br/></body></html>' \
+ % (cgi.escape(request.args["name"][0]),)
+
+root = Resource()
+root.putChild("form", FormPage())
+root.putChild("welcome", WelcomePage())
+factory = Site(root)
+endpoint = endpoints.TCP4ServerEndpoint(reactor, 8880)
+endpoint.listen(factory)
+reactor.run()
diff --git a/20171123/twisted-post.py b/20171123/twisted-post.py
new file mode 100755
index 0000000000000000000000000000000000000000..5b4dbd98a90fdbe316ce0c1c4ed0923baae4a42f
--- /dev/null
+++ b/20171123/twisted-post.py
@@ -0,0 +1,24 @@
+#!/usr/bin/python2
+
+from twisted.web.server import Site
+from twisted.web.resource import Resource
+from twisted.internet import reactor, endpoints
+
+import cgi
+
+class FormPage(Resource):
+ def render_GET(self, request):
+ return '<html><body><form method="POST">Your name: ' \
+ + '<input name="name" type="text" /><br/>' \
+ + '<input type="submit"></form></body></html>'
+
+ def render_POST(self, request):
+ return '<html><body>Hello, %s!</body></html>' \
+ % (cgi.escape(request.args["name"][0]),)
+
+root = Resource()
+root.putChild("form", FormPage())
+factory = Site(root)
+endpoint = endpoints.TCP4ServerEndpoint(reactor, 8880)
+endpoint.listen(factory)
+reactor.run()
diff --git a/20171123/welcome-post.cgi b/20171123/welcome-post.cgi
new file mode 100755
index 0000000000000000000000000000000000000000..85ba7f42ca297c14085859f24a977475c872e3ed
--- /dev/null
+++ b/20171123/welcome-post.cgi
@@ -0,0 +1,8 @@
+#!/bin/bash
+
+echo Content-Type: text/plain
+echo
+
+name=$(cut -d '&' -f 1 | sed -e "s/\<name=\(.*\)/\1/")
+
+echo "Hello, $name!"
diff --git a/20171123/welcome.cgi b/20171123/welcome.cgi
new file mode 100755
index 0000000000000000000000000000000000000000..fb90a257d20970931fad7cc5497e98301749e2c6
--- /dev/null
+++ b/20171123/welcome.cgi
@@ -0,0 +1,8 @@
+#!/bin/bash
+
+echo Content-Type: text/plain
+echo
+
+name=$(echo $QUERY_STRING | cut -d '&' -f 1 | sed -e "s/\<name=\(.*\)/\1/")
+
+echo "Hello, $name!"
diff --git a/20171123/welcome.php b/20171123/welcome.php
new file mode 100644
index 0000000000000000000000000000000000000000..de6e75cb85dc696080b2320ae3d767460d847303
--- /dev/null
+++ b/20171123/welcome.php
@@ -0,0 +1,5 @@
+<html>
+ <body>
+ Hello, <?php echo $_POST["name"]; ?>!
+ </body>
+</html>
diff --git a/20171123/xbee.jpg b/20171123/xbee.jpg
new file mode 120000
index 0000000000000000000000000000000000000000..ff0adff2eadf3d9b775d03cea8cf1f118534e2b9
--- /dev/null
+++ b/20171123/xbee.jpg
@@ -0,0 +1 @@
+../common/xbee.jpg
\ No newline at end of file