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/* Simple POSIX threads program.
*
*
* --------------------------------------------------------------------------
*
* Pthreads-win32 - POSIX Threads Library for Win32
* Copyright(C) 1998 John E. Bossom
* Copyright(C) 1999,2005 Pthreads-win32 contributors
*
* Contact Email: rpj@callisto.canberra.edu.au
*
* The current list of contributors is contained
* in the file CONTRIBUTORS included with the source
* code distribution. The list can also be seen at the
* following World Wide Web location:
* http://sources.redhat.com/pthreads-win32/contributors.html
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library in the file COPYING.LIB;
* if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*
* --------------------------------------------------------------------------
*
* Author: Eyal Lebedinsky eyal@eyal.emu.id.au
* Written: Sep 1998.
* Version Date: 12 Sep 1998
*
* Do we need to lock stdout or is it thread safe?
*
* Used:
* pthread_t
* pthread_attr_t
* pthread_create()
* pthread_join()
* pthread_mutex_t
* PTHREAD_MUTEX_INITIALIZER
* pthread_mutex_init() [not used now]
* pthread_mutex_destroy()
* pthread_mutex_lock()
* pthread_mutex_trylock()
* pthread_mutex_unlock()
*
* What this program does is establish a work queue (implemented using
* four mutexes for each thread). It then schedules work (by storing
* a number in 'todo') and releases the threads. When the work is done
* the threads will block. The program then repeats the same thing once
* more (just to test the logic) and when the work is done it destroyes
* the threads.
*
* The 'work' we do is simply burning CPU cycles in a loop.
* The 'todo' work queue is trivial - each threads pops one element
* off it by incrementing it, the poped number is the 'work' to do.
* When 'todo' reaches the limit (nwork) the queue is considered
* empty.
*
* The number displayed at the end is the amount of work each thread
* did, so we can see if the load was properly distributed.
*
* The program was written to test a threading setup (not seen here)
* rather than to demonstrate correct usage of the pthread facilities.
*
* Note how each thread is given access to a thread control structure
* (TC) which is used for communicating to/from the main program (e.g.
* the threads knows its 'id' and also filles in the 'work' done).
*/
#include "test.h"
#include <stdlib.h>
#include <math.h>
struct thread_control {
int id;
pthread_t thread; /* thread id */
pthread_mutex_t mutex_start;
pthread_mutex_t mutex_started;
pthread_mutex_t mutex_end;
pthread_mutex_t mutex_ended;
long work; /* work done */
int stat; /* pthread_init status */
};
typedef struct thread_control TC;
static TC *tcs = NULL;
static int nthreads = 10;
static int nwork = 100;
static int quiet = 0;
static int todo = -1;
static pthread_mutex_t mutex_todo = PTHREAD_MUTEX_INITIALIZER;
static pthread_mutex_t mutex_stdout = PTHREAD_MUTEX_INITIALIZER;
static void
die (int ret)
{
if (NULL != tcs)
{
free (tcs);
tcs = NULL;
}
if (ret)
exit (ret);
}
static double
waste_time (int n)
{
int i;
double f, g, h, s;
s = 0.0;
/*
* Useless work.
*/
for (i = n*100; i > 0; --i)
{
f = rand ();
g = rand ();
h = rand ();
s += 2.0 * f * g / (h != 0.0 ? (h * h) : 1.0);
}
return s;
}
static int
do_work_unit (int who, int n)
{
int i;
static int nchars = 0;
double f = 0.0;
if (quiet)
i = 0;
else {
/*
* get lock on stdout
*/
assert(pthread_mutex_lock (&mutex_stdout) == 0);
/*
* do our job
*/
i = printf ("%c", "0123456789abcdefghijklmnopqrstuvwxyz"[who]);
if (!(++nchars % 50))
printf ("\n");
fflush (stdout);
/*
* release lock on stdout
*/
assert(pthread_mutex_unlock (&mutex_stdout) == 0);
}
n = rand () % 10000; /* ignore incoming 'n' */
f = waste_time (n);
/* This prevents the statement above from being optimised out */
if (f > 0.0)
return(n);
return (n);
}
static int
print_server (void *ptr)
{
int mywork;
int n;
TC *tc = (TC *)ptr;
assert(pthread_mutex_lock (&tc->mutex_started) == 0);
for (;;)
{
assert(pthread_mutex_lock (&tc->mutex_start) == 0);
assert(pthread_mutex_unlock (&tc->mutex_start) == 0);
assert(pthread_mutex_lock (&tc->mutex_ended) == 0);
assert(pthread_mutex_unlock (&tc->mutex_started) == 0);
for (;;)
{
/*
* get lock on todo list
*/
assert(pthread_mutex_lock (&mutex_todo) == 0);
mywork = todo;
if (todo >= 0)
{
++todo;
if (todo >= nwork)
todo = -1;
}
assert(pthread_mutex_unlock (&mutex_todo) == 0);
if (mywork < 0)
break;
assert((n = do_work_unit (tc->id, mywork)) >= 0);
tc->work += n;
}
assert(pthread_mutex_lock (&tc->mutex_end) == 0);
assert(pthread_mutex_unlock (&tc->mutex_end) == 0);
assert(pthread_mutex_lock (&tc->mutex_started) == 0);
assert(pthread_mutex_unlock (&tc->mutex_ended) == 0);
if (-2 == mywork)
break;
}
assert(pthread_mutex_unlock (&tc->mutex_started) == 0);
return (0);
}
static void
dosync (void)
{
int i;
for (i = 0; i < nthreads; ++i)
{
assert(pthread_mutex_lock (&tcs[i].mutex_end) == 0);
assert(pthread_mutex_unlock (&tcs[i].mutex_start) == 0);
assert(pthread_mutex_lock (&tcs[i].mutex_started) == 0);
assert(pthread_mutex_unlock (&tcs[i].mutex_started) == 0);
}
/*
* Now threads do their work
*/
for (i = 0; i < nthreads; ++i)
{
assert(pthread_mutex_lock (&tcs[i].mutex_start) == 0);
assert(pthread_mutex_unlock (&tcs[i].mutex_end) == 0);
assert(pthread_mutex_lock (&tcs[i].mutex_ended) == 0);
assert(pthread_mutex_unlock (&tcs[i].mutex_ended) == 0);
}
}
static void
dowork (void)
{
todo = 0;
dosync();
todo = 0;
dosync();
}
int
main (int argc, char *argv[])
{
int i;
assert(NULL != (tcs = (TC *) calloc (nthreads, sizeof (*tcs))));
/*
* Launch threads
*/
for (i = 0; i < nthreads; ++i)
{
tcs[i].id = i;
assert(pthread_mutex_init (&tcs[i].mutex_start, NULL) == 0);
assert(pthread_mutex_init (&tcs[i].mutex_started, NULL) == 0);
assert(pthread_mutex_init (&tcs[i].mutex_end, NULL) == 0);
assert(pthread_mutex_init (&tcs[i].mutex_ended, NULL) == 0);
tcs[i].work = 0;
assert(pthread_mutex_lock (&tcs[i].mutex_start) == 0);
assert((tcs[i].stat =
pthread_create (&tcs[i].thread,
NULL,
(void *(*)(void *))print_server,
(void *) &tcs[i])
) == 0);
/*
* Wait for thread initialisation
*/
{
int trylock = 0;
while (trylock == 0)
{
trylock = pthread_mutex_trylock(&tcs[i].mutex_started);
assert(trylock == 0 || trylock == EBUSY);
if (trylock == 0)
{
assert(pthread_mutex_unlock (&tcs[i].mutex_started) == 0);
}
}
}
}
dowork ();
/*
* Terminate threads
*/
todo = -2; /* please terminate */
dosync();
for (i = 0; i < nthreads; ++i)
{
if (0 == tcs[i].stat)
assert(pthread_join (tcs[i].thread, NULL) == 0);
}
/*
* destroy locks
*/
assert(pthread_mutex_destroy (&mutex_stdout) == 0);
assert(pthread_mutex_destroy (&mutex_todo) == 0);
/*
* Cleanup
*/
printf ("\n");
/*
* Show results
*/
for (i = 0; i < nthreads; ++i)
{
printf ("%2d ", i);
if (0 == tcs[i].stat)
printf ("%10ld\n", tcs[i].work);
else
printf ("failed %d\n", tcs[i].stat);
assert(pthread_mutex_unlock(&tcs[i].mutex_start) == 0);
assert(pthread_mutex_destroy (&tcs[i].mutex_start) == 0);
assert(pthread_mutex_destroy (&tcs[i].mutex_started) == 0);
assert(pthread_mutex_destroy (&tcs[i].mutex_end) == 0);
assert(pthread_mutex_destroy (&tcs[i].mutex_ended) == 0);
}
die (0);
return (0);
}

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