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/* wg.c - Thread management tools modeled on
* https://golang.org/pkg/sync/#WaitGroup
*
* Copyright (C) 2016 Luke Shumaker
*
* This program is free software: you can redistribute it and/or modify
* it 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 program 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 program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <errno.h>
#include <error.h>
#include <stdlib.h> /* for EXIT_FAILURE */
#include <unistd.h>
#include "wg.h"
/* pthread_cond_t is overly complicated. Just use a self-pipe. */
static
void *wg_gc(void *wg_anon) {
struct wg *wg = wg_anon;
pthread_t thread;
while (1) {
ssize_t r = read(wg->fd_threads[0], &thread, sizeof(thread));
if (r < 0) {
if (errno == EINTR)
continue;
error(EXIT_FAILURE, errno, "wg_gc: read");
} else if ((size_t)r < sizeof(thread)) {
error(EXIT_FAILURE, 0, "wg_gc: read: only read %zd/%zu", r, sizeof(thread));
}
pthread_join(thread, NULL);
int p;
if ((p = pthread_mutex_lock(&wg->lock)) != 0)
error(EXIT_FAILURE, p, "wg_gc: pthread_mutex_lock");
wg->count--;
if (wg->count == 0) {
if ((p = pthread_mutex_unlock(&wg->lock)) != 0)
error(EXIT_FAILURE, p, "wg_gc: pthread_mutex_unlock");
return NULL;
}
if ((p = pthread_mutex_unlock(&wg->lock)) != 0)
error(EXIT_FAILURE, p, "wg_gc: pthread_mutex_unlock");
}
}
void wg_init(struct wg *wg) {
wg->count = 0;
int r;
if ((r = pthread_mutex_init(&wg->lock, NULL)) != 0)
error(EXIT_FAILURE, r, "wg_init: pthread_mutex_init");
if (pipe(wg->fd_threads) != 0)
error(EXIT_FAILURE, errno, "wg_init: pipe");
if ((r = pthread_create(&wg->gc, NULL, wg_gc, (void*)wg)) != 0)
error(EXIT_FAILURE, r, "wg_init: pthread_create");
}
void wg_add(struct wg *wg) {
int r;
if ((r = pthread_mutex_lock(&wg->lock)) != 0)
error(EXIT_FAILURE, r, "wg_add: pthread_mutex_lock");
wg->count++;
if ((r = pthread_mutex_unlock(&wg->lock)) != 0)
error(EXIT_FAILURE, r, "wg_add: pthread_mutex_unlock");
}
void wg_sub(struct wg *wg) {
pthread_t thread = pthread_self();
ssize_t r = write(wg->fd_threads[1], &thread, sizeof(thread));
if (r < 0) {
error(EXIT_FAILURE, errno, "wg_sub: write");
} else if ((size_t)r < sizeof(thread)) {
error(EXIT_FAILURE, 0, "wg_sub: only wrote %zd/%zu", r, sizeof(thread));
}
}
void wg_wait(struct wg *wg) {
int r;
if ((r = pthread_join(wg->gc, NULL)) != 0)
error(EXIT_FAILURE, r, "wg_wait: pthread_join");
if (close(wg->fd_threads[1]) != 0)
error(EXIT_FAILURE, errno, "wg_wait: close(fd_threads[1])");
if (close(wg->fd_threads[0]) != 0)
error(EXIT_FAILURE, errno, "wg_wait: close(fd_threads[0])");
if ((r = pthread_mutex_destroy(&wg->lock)) != 0)
error(EXIT_FAILURE, r, "wg_wait: pthread_mutex_destroy");
}
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