OpenCores
URL https://opencores.org/ocsvn/openrisc/openrisc/trunk

Subversion Repositories openrisc

[/] [openrisc/] [trunk/] [rtos/] [ecos-2.0/] [doc/] [html/] [user-guide/] [sample-twothreads.html] - Blame information for rev 510

Go to most recent revision | Details | Compare with Previous | View Log

Line No. Rev Author Line
1 28 unneback 
<!-- Copyright (C) 2003 Red Hat, Inc.                                -->
2 
<!-- This material may be distributed only subject to the terms      -->
3 
<!-- and conditions set forth in the Open Publication License, v1.0  -->
4 
<!-- or later (the latest version is presently available at          -->
5 
<!-- http://www.opencontent.org/openpub/).                           -->
6 
<!-- Distribution of the work or derivative of the work in any       -->
7 
<!-- standard (paper) book form is prohibited unless prior           -->
8 
<!-- permission is obtained from the copyright holder.               -->
9 
<HTML
10 
><HEAD
11 
><TITLE
12 
>A Sample Program with Two Threads</TITLE
13 
><meta name="MSSmartTagsPreventParsing" content="TRUE">
14 
<META
15 
NAME="GENERATOR"
16 
CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+
17 
"><LINK
18 
REL="HOME"
19 
TITLE="eCos User Guide"
20 
HREF="ecos-user-guide.html"><LINK
21 
REL="UP"
22 
TITLE="Building and Running Sample Applications"
23 
HREF="building-and-running-sample-appliations.html"><LINK
24 
REL="PREVIOUS"
25 
TITLE="Building and Running Sample Applications"
26 
HREF="building-and-running-sample-appliations.html"><LINK
27 
REL="NEXT"
28 
TITLE="More Features &#8212; Clocks and Alarm
29 
Handlers"
30 
HREF="clocks-and-alarm-handlers.html"></HEAD
31 
><BODY
32 
CLASS="SECT1"
33 
BGCOLOR="#FFFFFF"
34 
TEXT="#000000"
35 
LINK="#0000FF"
36 
VLINK="#840084"
37 
ALINK="#0000FF"
38 
><DIV
39 
CLASS="NAVHEADER"
40 
><TABLE
41 
SUMMARY="Header navigation table"
42 
WIDTH="100%"
43 
BORDER="0"
44 
CELLPADDING="0"
45 
CELLSPACING="0"
46 
><TR
47 
><TH
48 
COLSPAN="3"
49 
ALIGN="center"
50 
>eCos User Guide</TH
51 
></TR
52 
><TR
53 
><TD
54 
WIDTH="10%"
55 
ALIGN="left"
56 
VALIGN="bottom"
57 
><A
58 
HREF="building-and-running-sample-appliations.html"
59 
ACCESSKEY="P"
60 
>Prev</A
61 
></TD
62 
><TD
63 
WIDTH="80%"
64 
ALIGN="center"
65 
VALIGN="bottom"
66 
>Chapter 13. Building and Running Sample Applications</TD
67 
><TD
68 
WIDTH="10%"
69 
ALIGN="right"
70 
VALIGN="bottom"
71 
><A
72 
HREF="clocks-and-alarm-handlers.html"
73 
ACCESSKEY="N"
74 
>Next</A
75 
></TD
76 
></TR
77 
></TABLE
78 
><HR
79 
ALIGN="LEFT"
80 
WIDTH="100%"></DIV
81 
><DIV
82 
CLASS="SECT1"
83 
><H1
84 
CLASS="SECT1"
85 
><A
86 
NAME="SAMPLE-TWOTHREADS">A Sample Program with Two Threads</H1
87 
><P
88 
>Below is a program that uses some of <SPAN
89 
CLASS="PRODUCTNAME"
90 
>eCos</SPAN
91 
>' system calls. It
92 
creates two threads, each of which goes into an infinite loop in which
93 
it sleeps for a while (using cyg_thread_delay()).  This code is found
94 
in the file <TT
95 
CLASS="FILENAME"
96 
>twothreads.c</TT
97 
>
98 
in the examples directory.</P
99 
><DIV
100 
CLASS="SECT2"
101 
><H2
102 
CLASS="SECT2"
103 
><A
104 
NAME="AEN871"><SPAN
105 
CLASS="PRODUCTNAME"
106 
>eCos</SPAN
107 
> two-threaded program listing</H2
108 
><TABLE
109 
BORDER="5"
110 
BGCOLOR="#E0E0F0"
111 
WIDTH="70%"
112 
><TR
113 
><TD
114 
><PRE
115 
CLASS="PROGRAMLISTING"
116 
>#include &lt;cyg/kernel/kapi.h&#62;
117 
#include &lt;stdio.h&#62;
118 
#include &lt;math.h&#62;
119 
#include &lt;stdlib.h&#62;
120 
 
121 
/* now declare (and allocate space for) some kernel objects,
122 
  like the two threads we will use */
123 
cyg_thread thread_s[2]; /* space for two thread objects */
124 
 
125 
char stack[2][4096];    /* space for two 4K stacks */
126 
 
127 
/* now the handles for the threads */
128 
cyg_handle_t simple_threadA, simple_threadB;
129 
 
130 
/* and now variables for the procedure which is the thread */
131 
cyg_thread_entry_t simple_program;
132 
 
133 
/* and now a mutex to protect calls to the C library */
134 
cyg_mutex_t cliblock;
135 
 
136 
/* we install our own startup routine which sets up threads */
137 
void cyg_user_start(void)
138 
{
139 
 printf("Entering twothreads' cyg_user_start() function\n");
140 
 
141 
 cyg_mutex_init(&amp;cliblock);
142 
 
143 
 cyg_thread_create(4, simple_program, (cyg_addrword_t) 0,
144 
        "Thread A", (void *) stack[0], 4096,
145 
        &amp;simple_threadA, &amp;thread_s[0]);
146 
 cyg_thread_create(4, simple_program, (cyg_addrword_t) 1,
147 
        "Thread B", (void *) stack[1], 4096,
148 
        &amp;simple_threadB, &amp;thread_s[1]);
149 
 
150 
 cyg_thread_resume(simple_threadA);
151 
 cyg_thread_resume(simple_threadB);
152 
}
153 
 
154 
/* this is a simple program which runs in a thread */
155 
void simple_program(cyg_addrword_t data)
156 
{
157 
 int message = (int) data;
158 
 int delay;
159 
 
160 
 printf("Beginning execution; thread data is %d\n", message);
161 
 
162 
 cyg_thread_delay(200);
163 
 
164 
 for (;;) {
165 
 delay = 200 + (rand() % 50);
166 
 
167 
 /* note: printf() must be protected by a
168 
 call to cyg_mutex_lock() */
169 
 cyg_mutex_lock(&amp;cliblock); {
170 
 printf("Thread %d: and now a delay of %d clock ticks\n",
171 
        message, delay);
172 
 }
173 
 cyg_mutex_unlock(&amp;cliblock);
174 
 cyg_thread_delay(delay);
175 
 }
176 
}</PRE
177 
></TD
178 
></TR
179 
></TABLE
180 
><P
181 
>When you run the program (by typing <B
182 
CLASS="COMMAND"
183 
>continue</B
184 
> at
185 
the (<SPAN
186 
CLASS="emphasis"
187 
><I
188 
CLASS="EMPHASIS"
189 
>gdb</I
190 
></SPAN
191 
>) prompt) the output should look like
192 
this:</P
193 
><TABLE
194 
BORDER="5"
195 
BGCOLOR="#E0E0F0"
196 
WIDTH="70%"
197 
><TR
198 
><TD
199 
><PRE
200 
CLASS="PROGRAMLISTING"
201 
>Starting program: <TT
202 
CLASS="REPLACEABLE"
203 
><I
204 
>BASE_DIR</I
205 
></TT
206 
>/examples/twothreads.exe
207 
Entering twothreads' cyg_user_start()
208 
function
209 
Beginning execution; thread data is 0
210 
Beginning execution; thread data is 1
211 
Thread 0: and now a delay of 240 clock ticks
212 
Thread 1: and now a delay of 225 clock ticks
213 
Thread 1: and now a delay of 234 clock ticks
214 
Thread 0: and now a delay of 231 clock ticks
215 
Thread 1: and now a delay of 224 clock ticks
216 
Thread 0: and now a delay of 249 clock ticks
217 
Thread 1: and now a delay of 202 clock ticks
218 
Thread 0: and now a delay of 235 clock ticks</PRE
219 
></TD
220 
></TR
221 
></TABLE
222 
><DIV
223 
CLASS="NOTE"
224 
><BLOCKQUOTE
225 
CLASS="NOTE"
226 
><P
227 
><B
228 
>Note: </B
229 
>When running in a simulator the
230 
delays might be quite long. On a hardware board (where the clock
231 
speed is 100 ticks/second) the delays should average to
232 
about 2.25 seconds. In simulation, the delay will depend on the
233 
speed of the host processor and will almost always be much slower than
234 
the actual board. You might want to reduce the delay parameter when running
235 
in simulation.</P
236 
></BLOCKQUOTE
237 
></DIV
238 
><P
239 
><A
240 
HREF="sample-twothreads.html#FIGURE-TWOTHREADS-WITH-SIMPLE-PRINTS"
241 
>Figure 13-1</A
242 
> shows how this
243 
multitasking program executes.  Note that apart from the thread
244 
creation system calls, this program also creates and uses a
245 
<SPAN
246 
CLASS="emphasis"
247 
><I
248 
CLASS="EMPHASIS"
249 
>mutex</I
250 
></SPAN
251 
> for synchronization
252 
between the <TT
253 
CLASS="FUNCTION"
254 
>printf()</TT
255 
> calls in the two
256 
threads. This is because the C library standard I/O (by default) is
257 
configured not to be thread-safe, which means that if more than one
258 
thread is using standard I/O they might corrupt each other. This is
259 
fixed by a mutual exclusion (or <SPAN
260 
CLASS="emphasis"
261 
><I
262 
CLASS="EMPHASIS"
263 
>mutex</I
264 
></SPAN
265 
>) lockout
266 
mechanism: the threads do not call <TT
267 
CLASS="FUNCTION"
268 
>printf()</TT
269 
> until
270 
<TT
271 
CLASS="FUNCTION"
272 
>cyg_mutex_lock()</TT
273 
> has returned, which only happens
274 
when the other thread calls
275 
<TT
276 
CLASS="FUNCTION"
277 
>cyg_mutex_unlock()</TT
278 
>.</P
279 
><P
280 
>You could avoid using the mutex by configuring the C library to
281 
be thread-safe (by selecting the component
282 
<TT
283 
CLASS="LITERAL"
284 
>CYGSEM_LIBC_STDIO_THREAD_SAFE_STREAMS</TT
285 
>).</P
286 
><DIV
287 
CLASS="FIGURE"
288 
><A
289 
NAME="FIGURE-TWOTHREADS-WITH-SIMPLE-PRINTS"><P
290 
><B
291 
>Figure 13-1. Two
292 
threads with simple print statements after random delays</B
293 
></P
294 
><P
295 
><IMG
296 
SRC="pix/twothreads2.png"></P
297 
></DIV
298 
></DIV
299 
></DIV
300 
><DIV
301 
CLASS="NAVFOOTER"
302 
><HR
303 
ALIGN="LEFT"
304 
WIDTH="100%"><TABLE
305 
SUMMARY="Footer navigation table"
306 
WIDTH="100%"
307 
BORDER="0"
308 
CELLPADDING="0"
309 
CELLSPACING="0"
310 
><TR
311 
><TD
312 
WIDTH="33%"
313 
ALIGN="left"
314 
VALIGN="top"
315 
><A
316 
HREF="building-and-running-sample-appliations.html"
317 
ACCESSKEY="P"
318 
>Prev</A
319 
></TD
320 
><TD
321 
WIDTH="34%"
322 
ALIGN="center"
323 
VALIGN="top"
324 
><A
325 
HREF="ecos-user-guide.html"
326 
ACCESSKEY="H"
327 
>Home</A
328 
></TD
329 
><TD
330 
WIDTH="33%"
331 
ALIGN="right"
332 
VALIGN="top"
333 
><A
334 
HREF="clocks-and-alarm-handlers.html"
335 
ACCESSKEY="N"
336 
>Next</A
337 
></TD
338 
></TR
339 
><TR
340 
><TD
341 
WIDTH="33%"
342 
ALIGN="left"
343 
VALIGN="top"
344 
>Building and Running Sample Applications</TD
345 
><TD
346 
WIDTH="34%"
347 
ALIGN="center"
348 
VALIGN="top"
349 
><A
350 
HREF="building-and-running-sample-appliations.html"
351 
ACCESSKEY="U"
352 
>Up</A
353 
></TD
354 
><TD
355 
WIDTH="33%"
356 
ALIGN="right"
357 
VALIGN="top"
358 
>More Features &#8212; Clocks and Alarm
359 
Handlers</TD
360 
></TR
361 
></TABLE
362 
></DIV
363 
></BODY
364 
></HTML
365 
>

powered by: WebSVN 2.1.0

© copyright 1999-2024 OpenCores.org, equivalent to Oliscience, all rights reserved. OpenCores®, registered trademark.