mirror of
https://github.com/mpv-player/mpv
synced 2024-12-17 12:25:03 +00:00
92b9d75d72
There is not much of a reason to have these wrappers around. Use POSIX standard functions directly, and use a separate utility function to take care of the timespec calculations. (Course POSIX for using this weird format for time values.)
273 lines
11 KiB
C
273 lines
11 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 modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (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 General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with mpv. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <stdbool.h>
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#include <assert.h>
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#include "common/common.h"
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#include "osdep/threads.h"
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#include "osdep/timer.h"
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#include "dispatch.h"
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struct mp_dispatch_queue {
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struct mp_dispatch_item *head, *tail;
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pthread_mutex_t lock;
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pthread_cond_t cond;
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int suspend_requested;
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bool suspended;
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void (*wakeup_fn)(void *wakeup_ctx);
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void *wakeup_ctx;
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// This lock grant access to the target thread's state during suspend mode.
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// During suspend mode, the target thread is blocked in the function
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// mp_dispatch_queue_process(), however this function may be processing
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// dispatch queue items. This lock serializes the dispatch queue processing
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// and external mp_dispatch_lock() calls.
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// Invariant: can be held only while suspended==true, and suspend_requested
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// must be >0 (unless mp_dispatch_queue_process() locks it). In particular,
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// suspend mode must not be left while the lock is held.
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pthread_mutex_t exclusive_lock;
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};
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struct mp_dispatch_item {
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mp_dispatch_fn fn;
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void *fn_data;
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bool asynchronous;
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bool completed;
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struct mp_dispatch_item *next;
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};
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static void queue_dtor(void *p)
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{
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struct mp_dispatch_queue *queue = p;
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assert(!queue->head);
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assert(!queue->suspend_requested);
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assert(!queue->suspended);
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pthread_cond_destroy(&queue->cond);
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pthread_mutex_destroy(&queue->lock);
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pthread_mutex_destroy(&queue->exclusive_lock);
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}
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// A dispatch queue lets other threads runs callbacks in a target thread.
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// The target thread is the thread which created the queue and which calls
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// mp_dispatch_queue_process().
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// Free the dispatch queue with talloc_free(). (It must be empty.)
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struct mp_dispatch_queue *mp_dispatch_create(void *ta_parent)
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{
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struct mp_dispatch_queue *queue = talloc_ptrtype(ta_parent, queue);
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*queue = (struct mp_dispatch_queue){0};
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talloc_set_destructor(queue, queue_dtor);
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pthread_mutex_init(&queue->exclusive_lock, NULL);
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pthread_mutex_init(&queue->lock, NULL);
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pthread_cond_init(&queue->cond, NULL);
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return queue;
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}
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// Set a custom function that should be called to guarantee that the target
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// thread wakes up. This is intended for use with code that needs to block
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// on non-pthread primitives, such as e.g. select(). In the case of select(),
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// the wakeup_fn could for example write a byte into a "wakeup" pipe in order
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// to unblock the select(). The wakeup_fn is called from the dispatch queue
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// when there are new dispatch items, and the target thread should then enter
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// mp_dispatch_queue_process() as soon as possible. Note that wakeup_fn is
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// called under no lock, so you might have to do synchronization yourself.
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void mp_dispatch_set_wakeup_fn(struct mp_dispatch_queue *queue,
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void (*wakeup_fn)(void *wakeup_ctx),
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void *wakeup_ctx)
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{
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queue->wakeup_fn = wakeup_fn;
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queue->wakeup_ctx = wakeup_ctx;
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}
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static void mp_dispatch_append(struct mp_dispatch_queue *queue,
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struct mp_dispatch_item *item)
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{
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pthread_mutex_lock(&queue->lock);
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if (queue->tail) {
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queue->tail->next = item;
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} else {
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queue->head = item;
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}
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queue->tail = item;
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// Wake up the main thread; note that other threads might wait on this
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// condition for reasons, so broadcast the condition.
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pthread_cond_broadcast(&queue->cond);
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pthread_mutex_unlock(&queue->lock);
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if (queue->wakeup_fn)
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queue->wakeup_fn(queue->wakeup_ctx);
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}
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// Enqueue a callback to run it on the target thread asynchronously. The target
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// thread will run fn(fn_data) as soon as it enter mp_dispatch_queue_process.
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// Note that mp_dispatch_enqueue() will usually return long before that happens.
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// It's up to the user to signal completion of the callback. It's also up to
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// the user to guarantee that the context fn_data has correct lifetime, i.e.
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// lives until the callback is run, and is freed after that.
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void mp_dispatch_enqueue(struct mp_dispatch_queue *queue,
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mp_dispatch_fn fn, void *fn_data)
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{
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struct mp_dispatch_item *item = talloc_ptrtype(NULL, item);
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*item = (struct mp_dispatch_item){
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.fn = fn,
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.fn_data = fn_data,
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.asynchronous = true,
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};
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mp_dispatch_append(queue, item);
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}
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// Like mp_dispatch_enqueue(), but the queue code will call talloc_free(fn_data)
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// after the fn callback has been run. (The callback could trivially do that
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// itself, but it makes it easier to implement synchronous and asynchronous
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// requests with the same callback implementation.)
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void mp_dispatch_enqueue_autofree(struct mp_dispatch_queue *queue,
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mp_dispatch_fn fn, void *fn_data)
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{
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struct mp_dispatch_item *item = talloc_ptrtype(NULL, item);
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*item = (struct mp_dispatch_item){
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.fn = fn,
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.fn_data = talloc_steal(item, fn_data),
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.asynchronous = true,
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};
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mp_dispatch_append(queue, item);
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}
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// Run fn(fn_data) on the target thread synchronously. This function enqueues
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// the callback and waits until the target thread is done doing this.
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// This is redundant to calling the function inside mp_dispatch_[un]lock(),
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// but can be helpful with code that relies on TLS (such as OpenGL).
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void mp_dispatch_run(struct mp_dispatch_queue *queue,
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mp_dispatch_fn fn, void *fn_data)
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{
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struct mp_dispatch_item item = {
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.fn = fn,
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.fn_data = fn_data,
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};
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mp_dispatch_append(queue, &item);
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pthread_mutex_lock(&queue->lock);
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while (!item.completed)
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pthread_cond_wait(&queue->cond, &queue->lock);
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pthread_mutex_unlock(&queue->lock);
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}
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// Process any outstanding dispatch items in the queue. This also handles
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// suspending or locking the target thread.
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// The timeout specifies the minimum wait time. The actual time spent in this
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// function can be much higher if the suspending/locking functions are used, or
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// if executing the dispatch items takes time. On the other hand, this function
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// can return much earlier than the timeout due to sporadic wakeups.
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// It is also guaranteed that if at least one queue item was processed, the
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// function will return as soon as possible, ignoring the timeout. This
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// simplifies users, such as re-checking conditions before waiting. (It will
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// still process the remaining queue items, and wait for unsuspend.)
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void mp_dispatch_queue_process(struct mp_dispatch_queue *queue, double timeout)
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{
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int64_t wait = timeout > 0 ? mp_add_timeout(mp_time_us(), timeout) : 0;
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pthread_mutex_lock(&queue->lock);
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queue->suspended = true;
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// Wake up thread which called mp_dispatch_suspend().
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pthread_cond_broadcast(&queue->cond);
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while (queue->head || queue->suspend_requested || wait > 0) {
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if (queue->head) {
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struct mp_dispatch_item *item = queue->head;
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queue->head = item->next;
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if (!queue->head)
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queue->tail = NULL;
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item->next = NULL;
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// Unlock, because we want to allow other threads to queue items
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// while the dispatch item is processed.
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// At the same time, exclusive_lock must be held to protect the
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// thread's user state.
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pthread_mutex_unlock(&queue->lock);
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pthread_mutex_lock(&queue->exclusive_lock);
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item->fn(item->fn_data);
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pthread_mutex_unlock(&queue->exclusive_lock);
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pthread_mutex_lock(&queue->lock);
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if (item->asynchronous) {
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talloc_free(item);
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} else {
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item->completed = true;
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// Wakeup mp_dispatch_run()
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pthread_cond_broadcast(&queue->cond);
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}
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} else {
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if (wait > 0) {
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struct timespec ts = mp_time_us_to_timespec(wait);
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pthread_cond_timedwait(&queue->cond, &queue->lock, &ts);
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} else {
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pthread_cond_wait(&queue->cond, &queue->lock);
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}
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}
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wait = 0;
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}
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queue->suspended = false;
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pthread_mutex_unlock(&queue->lock);
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}
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// Set the target thread into suspend mode: in this mode, the thread will enter
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// mp_dispatch_queue_process(), process any outstanding dispatch items, and
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// wait for new items when done (instead of exiting the process function).
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// Multiple threads can enter suspend mode at the same time. Suspend mode is
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// not a synchronization mechanism; it merely makes sure the target thread does
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// not leave mp_dispatch_queue_process(), even if it's done. mp_dispatch_lock()
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// can be used for exclusive access.
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void mp_dispatch_suspend(struct mp_dispatch_queue *queue)
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{
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pthread_mutex_lock(&queue->lock);
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queue->suspend_requested++;
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while (!queue->suspended) {
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pthread_mutex_unlock(&queue->lock);
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if (queue->wakeup_fn)
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queue->wakeup_fn(queue->wakeup_ctx);
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pthread_mutex_lock(&queue->lock);
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if (queue->suspended)
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break;
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pthread_cond_wait(&queue->cond, &queue->lock);
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}
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pthread_mutex_unlock(&queue->lock);
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}
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// Undo mp_dispatch_suspend().
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void mp_dispatch_resume(struct mp_dispatch_queue *queue)
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{
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pthread_mutex_lock(&queue->lock);
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assert(queue->suspended);
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assert(queue->suspend_requested > 0);
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queue->suspend_requested--;
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if (queue->suspend_requested == 0)
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pthread_cond_broadcast(&queue->cond);
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pthread_mutex_unlock(&queue->lock);
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}
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// Grant exclusive access to the target thread's state. While this is active,
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// no other thread can return from mp_dispatch_lock() (i.e. it behaves like
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// a pthread mutex), and no other thread can get dispatch items completed.
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// Other threads can still queue asynchronous dispatch items without waiting,
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// and the mutex behavior applies to this function only.
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void mp_dispatch_lock(struct mp_dispatch_queue *queue)
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{
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mp_dispatch_suspend(queue);
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pthread_mutex_lock(&queue->exclusive_lock);
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}
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// Undo mp_dispatch_lock().
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void mp_dispatch_unlock(struct mp_dispatch_queue *queue)
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{
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pthread_mutex_unlock(&queue->exclusive_lock);
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mp_dispatch_resume(queue);
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}
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