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/*
* This file is part of mpv.
*
* mpv 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 2.1 of the License, or (at your option) any later version.
*
* mpv 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 mpv. If not, see <http://www.gnu.org/licenses/>.
*/
#include <pthread.h>
#include "common/common.h"
#include "thread_pool.h"
struct work {
void (*fn)(void *ctx);
void *fn_ctx;
};
struct mp_thread_pool {
pthread_t *threads;
int num_threads;
pthread_mutex_t lock;
pthread_cond_t wakeup;
// --- the following fields are protected by lock
bool terminate;
struct work *work;
int num_work;
};
static void *worker_thread(void *arg)
{
struct mp_thread_pool *pool = arg;
pthread_mutex_lock(&pool->lock);
while (1) {
while (!pool->num_work && !pool->terminate)
pthread_cond_wait(&pool->wakeup, &pool->lock);
if (!pool->num_work && pool->terminate)
break;
assert(pool->num_work > 0);
struct work work = pool->work[pool->num_work - 1];
pool->num_work -= 1;
pthread_mutex_unlock(&pool->lock);
work.fn(work.fn_ctx);
pthread_mutex_lock(&pool->lock);
}
assert(pool->num_work == 0);
pthread_mutex_unlock(&pool->lock);
return NULL;
}
static void thread_pool_dtor(void *ctx)
{
struct mp_thread_pool *pool = ctx;
pthread_mutex_lock(&pool->lock);
pool->terminate = true;
pthread_cond_broadcast(&pool->wakeup);
pthread_mutex_unlock(&pool->lock);
for (int n = 0; n < pool->num_threads; n++)
pthread_join(pool->threads[n], NULL);
assert(pool->num_work == 0);
pthread_cond_destroy(&pool->wakeup);
pthread_mutex_destroy(&pool->lock);
}
// Create a thread pool with the given number of worker threads. This can return
// NULL if the worker threads could not be created. The thread pool can be
// destroyed with talloc_free(pool), or indirectly with talloc_free(ta_parent).
// If there are still work items on freeing, it will block until all work items
// are done, and the threads terminate.
struct mp_thread_pool *mp_thread_pool_create(void *ta_parent, int threads)
{
assert(threads > 0);
struct mp_thread_pool *pool = talloc_zero(ta_parent, struct mp_thread_pool);
talloc_set_destructor(pool, thread_pool_dtor);
pthread_mutex_init(&pool->lock, NULL);
pthread_cond_init(&pool->wakeup, NULL);
for (int n = 0; n < threads; n++) {
pthread_t thread;
if (pthread_create(&thread, NULL, worker_thread, pool)) {
talloc_free(pool);
return NULL;
}
MP_TARRAY_APPEND(pool, pool->threads, pool->num_threads, thread);
}
return pool;
}
// Queue a function to be run on a worker thread: fn(fn_ctx)
// If no worker thread is currently available, it's appended to a list in memory
// with unbounded size. This function always returns immediately.
// Concurrent queue calls are allowed, as long as it does not overlap with
// pool destruction.
void mp_thread_pool_queue(struct mp_thread_pool *pool, void (*fn)(void *ctx),
void *fn_ctx)
{
pthread_mutex_lock(&pool->lock);
struct work work = {fn, fn_ctx};
MP_TARRAY_INSERT_AT(pool, pool->work, pool->num_work, 0, work);
pthread_cond_signal(&pool->wakeup);
pthread_mutex_unlock(&pool->lock);
}
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