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/* $OpenBSD: pthread_rwlock2.c,v 1.1 2019/03/04 08:23:05 semarie Exp $ */
/*
* Copyright (c) 2019 Sebastien Marie <semarie@online.fr>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <err.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define LOOP_MAIN 64 /* number of loop to try */
#define NTHREADS 16 /* number of concurrents threads */
/*
* start several threads that share a buffer protected by rwlock.
*
* for each thread, take lock rw to set the buffer, and next take lock
* rd to read (print) the buffer content.
*/
static pthread_rwlock_t rwlock = PTHREAD_RWLOCK_INITIALIZER;
static char msg[128] = "default message";
void
set_msg(int self_n, char *new_msg)
{
pthread_t self = pthread_self();
if (pthread_rwlock_wrlock(&rwlock) != 0)
err(EXIT_FAILURE, "set_msg: pthread_rwlock_wrlock");
printf("%p: %d: set_msg\n", self, self_n);
strlcpy(msg, new_msg, sizeof(msg));
if (pthread_rwlock_unlock(&rwlock) != 0)
err(EXIT_FAILURE, "set_msg: pthread_rwlock_unlock");
}
void
print_msg(int self_n)
{
pthread_t self = pthread_self();
if (pthread_rwlock_rdlock(&rwlock) != 0)
err(EXIT_FAILURE, "print_msg: pthread_rwlock_rdlock");
printf("%p: %d: msg: \"%s\"\n", self, self_n, msg);
if (pthread_rwlock_unlock(&rwlock) != 0)
err(EXIT_FAILURE, "print_msg: pthread_rwlock_unlock");
}
void *
run(void *data)
{
int self_n = (int)data;
pthread_t self = pthread_self();
printf("%p: %d: enter run()\n", self, self_n);
set_msg(self_n, "new message");
print_msg(self_n);
printf("%p: %d: exit run()\n", self, self_n);
return NULL;
}
int
main(int argc, char *argv[])
{
int i, j;
/* enable some rthread debug code (env take precedence) */
if (setenv("RTHREAD_DEBUG", "9", 0) == -1)
err(EXIT_FAILURE, "setenv");
/* test in loop */
for (i=0; i < LOOP_MAIN; i++) {
pthread_t handlers[NTHREADS];
printf("main: %d\n", i);
/* launch a serie of threads */
for (j=0; j < NTHREADS; j++) {
if (pthread_create(&(handlers[j]), NULL,
&run, (void *)(long)j) != 0)
err(EXIT_FAILURE, "main: pthread_create");
}
/* wait for them to finish */
for (j=0; j < NTHREADS; j++) {
if (pthread_join(handlers[j], NULL) != 0)
err(EXIT_FAILURE, "main: pthread_join");
}
}
return EXIT_SUCCESS;
}
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