mirror of https://github.com/mpv-player/mpv
126 lines
3.7 KiB
C
126 lines
3.7 KiB
C
/*
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* This file is part of mpv.
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*
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* mpv is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* mpv is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with mpv. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <pthread.h>
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#include "common/common.h"
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#include "thread_pool.h"
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struct work {
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void (*fn)(void *ctx);
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void *fn_ctx;
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};
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struct mp_thread_pool {
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pthread_t *threads;
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int num_threads;
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pthread_mutex_t lock;
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pthread_cond_t wakeup;
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// --- the following fields are protected by lock
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bool terminate;
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struct work *work;
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int num_work;
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};
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static void *worker_thread(void *arg)
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{
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struct mp_thread_pool *pool = arg;
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pthread_mutex_lock(&pool->lock);
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while (1) {
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while (!pool->num_work && !pool->terminate)
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pthread_cond_wait(&pool->wakeup, &pool->lock);
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if (!pool->num_work && pool->terminate)
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break;
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assert(pool->num_work > 0);
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struct work work = pool->work[pool->num_work - 1];
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pool->num_work -= 1;
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pthread_mutex_unlock(&pool->lock);
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work.fn(work.fn_ctx);
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pthread_mutex_lock(&pool->lock);
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}
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assert(pool->num_work == 0);
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pthread_mutex_unlock(&pool->lock);
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return NULL;
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}
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static void thread_pool_dtor(void *ctx)
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{
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struct mp_thread_pool *pool = ctx;
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pthread_mutex_lock(&pool->lock);
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pool->terminate = true;
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pthread_cond_broadcast(&pool->wakeup);
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pthread_mutex_unlock(&pool->lock);
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for (int n = 0; n < pool->num_threads; n++)
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pthread_join(pool->threads[n], NULL);
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assert(pool->num_work == 0);
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pthread_cond_destroy(&pool->wakeup);
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pthread_mutex_destroy(&pool->lock);
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}
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// Create a thread pool with the given number of worker threads. This can return
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// NULL if the worker threads could not be created. The thread pool can be
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// destroyed with talloc_free(pool), or indirectly with talloc_free(ta_parent).
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// If there are still work items on freeing, it will block until all work items
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// are done, and the threads terminate.
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struct mp_thread_pool *mp_thread_pool_create(void *ta_parent, int threads)
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{
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assert(threads > 0);
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struct mp_thread_pool *pool = talloc_zero(ta_parent, struct mp_thread_pool);
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talloc_set_destructor(pool, thread_pool_dtor);
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pthread_mutex_init(&pool->lock, NULL);
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pthread_cond_init(&pool->wakeup, NULL);
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for (int n = 0; n < threads; n++) {
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pthread_t thread;
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if (pthread_create(&thread, NULL, worker_thread, pool)) {
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talloc_free(pool);
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return NULL;
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}
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MP_TARRAY_APPEND(pool, pool->threads, pool->num_threads, thread);
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}
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return pool;
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}
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// Queue a function to be run on a worker thread: fn(fn_ctx)
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// If no worker thread is currently available, it's appended to a list in memory
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// with unbounded size. This function always returns immediately.
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// Concurrent queue calls are allowed, as long as it does not overlap with
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// pool destruction.
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void mp_thread_pool_queue(struct mp_thread_pool *pool, void (*fn)(void *ctx),
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void *fn_ctx)
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{
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pthread_mutex_lock(&pool->lock);
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struct work work = {fn, fn_ctx};
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MP_TARRAY_INSERT_AT(pool, pool->work, pool->num_work, 0, work);
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pthread_cond_signal(&pool->wakeup);
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pthread_mutex_unlock(&pool->lock);
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}
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