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#include <stdbool.h>#include <assert.h>
#include "common/common.h"#include "osdep/threads.h"#include "osdep/timer.h"
#include "dispatch.h"
struct mp_dispatch_queue { struct mp_dispatch_item *head, *tail; pthread_mutex_t lock; pthread_cond_t cond; void (*wakeup_fn)(void *wakeup_ctx); void *wakeup_ctx; void (*onlock_fn)(void *onlock_ctx); void *onlock_ctx; // Time at which mp_dispatch_queue_process() should return. int64_t wait; // Make mp_dispatch_queue_process() exit if it's idle. bool interrupted; // The target thread is in mp_dispatch_queue_process() (and either idling, // locked, or running a dispatch callback). bool in_process; pthread_t in_process_thread; // The target thread is in mp_dispatch_queue_process(), and currently // something has exclusive access to it (e.g. running a dispatch callback, // or a different thread got it with mp_dispatch_lock()). bool locked; // A mp_dispatch_lock() call is requesting an exclusive lock. size_t lock_requests; // locked==true is due to a mp_dispatch_lock() call (for debugging). bool locked_explicit; pthread_t locked_explicit_thread;};
struct mp_dispatch_item { mp_dispatch_fn fn; void *fn_data; bool asynchronous; bool mergeable; bool completed; struct mp_dispatch_item *next;};
static void queue_dtor(void *p){ struct mp_dispatch_queue *queue = p; assert(!queue->head); assert(!queue->in_process); assert(!queue->lock_requests); assert(!queue->locked); pthread_cond_destroy(&queue->cond); pthread_mutex_destroy(&queue->lock);}
// A dispatch queue lets other threads run callbacks in a target thread.// The target thread is the thread which calls mp_dispatch_queue_process().// Free the dispatch queue with talloc_free(). At the time of destruction,// the queue must be empty. The easiest way to guarantee this is to// terminate all potential senders, then call mp_dispatch_run() with a// function that e.g. makes the target thread exit, then pthread_join() the// target thread, and finally destroy the queue. Another way is calling// mp_dispatch_queue_process() after terminating all potential senders, and// then destroying the queue.struct mp_dispatch_queue *mp_dispatch_create(void *ta_parent){ struct mp_dispatch_queue *queue = talloc_ptrtype(ta_parent, queue); *queue = (struct mp_dispatch_queue){0}; talloc_set_destructor(queue, queue_dtor); pthread_mutex_init(&queue->lock, NULL); pthread_cond_init(&queue->cond, NULL); return queue;}
// Set a custom function that should be called to guarantee that the target// thread wakes up. This is intended for use with code that needs to block// on non-pthread primitives, such as e.g. select(). In the case of select(),// the wakeup_fn could for example write a byte into a "wakeup" pipe in order// to unblock the select(). The wakeup_fn is called from the dispatch queue// when there are new dispatch items, and the target thread should then enter// mp_dispatch_queue_process() as soon as possible.// Note that this setter does not do internal synchronization, so you must set// it before other threads see it.void mp_dispatch_set_wakeup_fn(struct mp_dispatch_queue *queue, void (*wakeup_fn)(void *wakeup_ctx), void *wakeup_ctx){ queue->wakeup_fn = wakeup_fn; queue->wakeup_ctx = wakeup_ctx;}
// Set a function that will be called by mp_dispatch_lock() if the target thread// is not calling mp_dispatch_queue_process() right now. This is an obscure,// optional mechanism to make a worker thread react to external events more// quickly. The idea is that the callback will make the worker thread to stop// doing whatever (e.g. by setting a flag), and call mp_dispatch_queue_process()// in order to let mp_dispatch_lock() calls continue sooner.// Like wakeup_fn, this setter does no internal synchronization, and you must// not access the dispatch queue itself from the callback.void mp_dispatch_set_onlock_fn(struct mp_dispatch_queue *queue, void (*onlock_fn)(void *onlock_ctx), void *onlock_ctx){ queue->onlock_fn = onlock_fn; queue->onlock_ctx = onlock_ctx;}
static void mp_dispatch_append(struct mp_dispatch_queue *queue, struct mp_dispatch_item *item){ pthread_mutex_lock(&queue->lock); if (item->mergeable) { for (struct mp_dispatch_item *cur = queue->head; cur; cur = cur->next) { if (cur->mergeable && cur->fn == item->fn && cur->fn_data == item->fn_data) { talloc_free(item); pthread_mutex_unlock(&queue->lock); return; } } }
if (queue->tail) { queue->tail->next = item; } else { queue->head = item; } queue->tail = item;
// Wake up the main thread; note that other threads might wait on this // condition for reasons, so broadcast the condition. pthread_cond_broadcast(&queue->cond); // No wakeup callback -> assume mp_dispatch_queue_process() needs to be // interrupted instead. if (!queue->wakeup_fn) queue->interrupted = true; pthread_mutex_unlock(&queue->lock);
if (queue->wakeup_fn) queue->wakeup_fn(queue->wakeup_ctx);}
// Enqueue a callback to run it on the target thread asynchronously. The target// thread will run fn(fn_data) as soon as it enter mp_dispatch_queue_process.// Note that mp_dispatch_enqueue() will usually return long before that happens.// It's up to the user to signal completion of the callback. It's also up to// the user to guarantee that the context fn_data has correct lifetime, i.e.// lives until the callback is run, and is freed after that.void mp_dispatch_enqueue(struct mp_dispatch_queue *queue, mp_dispatch_fn fn, void *fn_data){ struct mp_dispatch_item *item = talloc_ptrtype(NULL, item); *item = (struct mp_dispatch_item){ .fn = fn, .fn_data = fn_data, .asynchronous = true, }; mp_dispatch_append(queue, item);}
// Like mp_dispatch_enqueue(), but the queue code will call talloc_free(fn_data)// after the fn callback has been run. (The callback could trivially do that// itself, but it makes it easier to implement synchronous and asynchronous// requests with the same callback implementation.)void mp_dispatch_enqueue_autofree(struct mp_dispatch_queue *queue, mp_dispatch_fn fn, void *fn_data){ struct mp_dispatch_item *item = talloc_ptrtype(NULL, item); *item = (struct mp_dispatch_item){ .fn = fn, .fn_data = talloc_steal(item, fn_data), .asynchronous = true, }; mp_dispatch_append(queue, item);}
// Like mp_dispatch_enqueue(), butvoid mp_dispatch_enqueue_notify(struct mp_dispatch_queue *queue, mp_dispatch_fn fn, void *fn_data){ struct mp_dispatch_item *item = talloc_ptrtype(NULL, item); *item = (struct mp_dispatch_item){ .fn = fn, .fn_data = fn_data, .mergeable = true, .asynchronous = true, }; mp_dispatch_append(queue, item);}
// Remove already queued item. Only items enqueued with the following functions// can be canceled:// - mp_dispatch_enqueue()// - mp_dispatch_enqueue_notify()// Items which were enqueued, and which are currently executing, can not be// canceled anymore. This function is mostly for being called from the same// context as mp_dispatch_queue_process(), where the "currently executing" case// can be excluded.void mp_dispatch_cancel_fn(struct mp_dispatch_queue *queue, mp_dispatch_fn fn, void *fn_data){ pthread_mutex_lock(&queue->lock); struct mp_dispatch_item **pcur = &queue->head; queue->tail = NULL; while (*pcur) { struct mp_dispatch_item *cur = *pcur; if (cur->fn == fn && cur->fn_data == fn_data) { *pcur = cur->next; talloc_free(cur); } else { queue->tail = cur; pcur = &cur->next; } } pthread_mutex_unlock(&queue->lock);}
// Run fn(fn_data) on the target thread synchronously. This function enqueues// the callback and waits until the target thread is done doing this.// This is redundant to calling the function inside mp_dispatch_[un]lock(),// but can be helpful with code that relies on TLS (such as OpenGL).void mp_dispatch_run(struct mp_dispatch_queue *queue, mp_dispatch_fn fn, void *fn_data){ struct mp_dispatch_item item = { .fn = fn, .fn_data = fn_data, }; mp_dispatch_append(queue, &item);
pthread_mutex_lock(&queue->lock); while (!item.completed) pthread_cond_wait(&queue->cond, &queue->lock); pthread_mutex_unlock(&queue->lock);}
// Process any outstanding dispatch items in the queue. This also handles// suspending or locking the this thread from another thread via// mp_dispatch_lock().// The timeout specifies the minimum wait time. The actual time spent in this// function can be much higher if the suspending/locking functions are used, or// if executing the dispatch items takes time. On the other hand, this function// can return much earlier than the timeout due to sporadic wakeups.// Note that this will strictly return only after:// - timeout has passed,// - all queue items were processed,// - the possibly acquired lock has been released// It's possible to cancel the timeout by calling mp_dispatch_interrupt().// Reentrant calls are not allowed. There can be only 1 thread calling// mp_dispatch_queue_process() at a time. In addition, mp_dispatch_lock() can// not be called from a thread that is calling mp_dispatch_queue_process() (i.e.// no enqueued callback can call the lock/unlock functions).void mp_dispatch_queue_process(struct mp_dispatch_queue *queue, double timeout){ pthread_mutex_lock(&queue->lock); queue->wait = timeout > 0 ? mp_add_timeout(mp_time_us(), timeout) : 0; assert(!queue->in_process); // recursion not allowed queue->in_process = true; queue->in_process_thread = pthread_self(); // Wake up thread which called mp_dispatch_lock(). if (queue->lock_requests) pthread_cond_broadcast(&queue->cond); while (1) { if (queue->lock_requests) { // Block due to something having called mp_dispatch_lock(). pthread_cond_wait(&queue->cond, &queue->lock); } else if (queue->head) { struct mp_dispatch_item *item = queue->head; queue->head = item->next; if (!queue->head) queue->tail = NULL; item->next = NULL; // Unlock, because we want to allow other threads to queue items // while the dispatch item is processed. // At the same time, we must prevent other threads from returning // from mp_dispatch_lock(), which is done by locked=true. assert(!queue->locked); queue->locked = true; pthread_mutex_unlock(&queue->lock);
item->fn(item->fn_data);
pthread_mutex_lock(&queue->lock); assert(queue->locked); queue->locked = false; // Wakeup mp_dispatch_run(), also mp_dispatch_lock(). pthread_cond_broadcast(&queue->cond); if (item->asynchronous) { talloc_free(item); } else { item->completed = true; } } else if (queue->wait > 0 && !queue->interrupted) { struct timespec ts = mp_time_us_to_timespec(queue->wait); if (pthread_cond_timedwait(&queue->cond, &queue->lock, &ts)) queue->wait = 0; } else { break; } } assert(!queue->locked); queue->in_process = false; queue->interrupted = false; pthread_mutex_unlock(&queue->lock);}
// If the queue is inside of mp_dispatch_queue_process(), make it return as// soon as all work items have been run, without waiting for the timeout. This// does not make it return early if it's blocked by a mp_dispatch_lock().// If the queue is _not_ inside of mp_dispatch_queue_process(), make the next// call of it use a timeout of 0 (this is useful behavior if you need to// wakeup the main thread from another thread in a race free way).void mp_dispatch_interrupt(struct mp_dispatch_queue *queue){ pthread_mutex_lock(&queue->lock); queue->interrupted = true; pthread_cond_broadcast(&queue->cond); pthread_mutex_unlock(&queue->lock);}
// If a mp_dispatch_queue_process() call is in progress, then adjust the maximum// time it blocks due to its timeout argument. Otherwise does nothing. (It// makes sense to call this in code that uses both mp_dispatch_[un]lock() and// a normal event loop.)// Does not work correctly with queues that have mp_dispatch_set_wakeup_fn()// called on them, because this implies you actually do waiting via// mp_dispatch_queue_process(), while wakeup callbacks are used when you need// to wait in external APIs.void mp_dispatch_adjust_timeout(struct mp_dispatch_queue *queue, int64_t until){ pthread_mutex_lock(&queue->lock); if (queue->in_process && queue->wait > until) { queue->wait = until; pthread_cond_broadcast(&queue->cond); } pthread_mutex_unlock(&queue->lock);}
// Grant exclusive access to the target thread's state. While this is active,// no other thread can return from mp_dispatch_lock() (i.e. it behaves like// a pthread mutex), and no other thread can get dispatch items completed.// Other threads can still queue asynchronous dispatch items without waiting,// and the mutex behavior applies to this function and dispatch callbacks only.// The lock is non-recursive, and dispatch callback functions can be thought of// already holding the dispatch lock.void mp_dispatch_lock(struct mp_dispatch_queue *queue){ pthread_mutex_lock(&queue->lock); // Must not be called recursively from dispatched callbacks. if (queue->in_process) assert(!pthread_equal(queue->in_process_thread, pthread_self())); // Must not be called recursively at all. if (queue->locked_explicit) assert(!pthread_equal(queue->locked_explicit_thread, pthread_self())); queue->lock_requests += 1; // And now wait until the target thread gets "trapped" within the // mp_dispatch_queue_process() call, which will mean we get exclusive // access to the target's thread state. if (queue->onlock_fn) queue->onlock_fn(queue->onlock_ctx); while (!queue->in_process) { pthread_mutex_unlock(&queue->lock); if (queue->wakeup_fn) queue->wakeup_fn(queue->wakeup_ctx); pthread_mutex_lock(&queue->lock); if (queue->in_process) break; pthread_cond_wait(&queue->cond, &queue->lock); } // Wait until we can get the lock. while (!queue->in_process || queue->locked) pthread_cond_wait(&queue->cond, &queue->lock); // "Lock". assert(queue->lock_requests); assert(!queue->locked); assert(!queue->locked_explicit); queue->locked = true; queue->locked_explicit = true; queue->locked_explicit_thread = pthread_self(); pthread_mutex_unlock(&queue->lock);}
// Undo mp_dispatch_lock().void mp_dispatch_unlock(struct mp_dispatch_queue *queue){ pthread_mutex_lock(&queue->lock); assert(queue->locked); // Must be called after a mp_dispatch_lock(), from the same thread. assert(queue->locked_explicit); assert(pthread_equal(queue->locked_explicit_thread, pthread_self())); // "Unlock". queue->locked = false; queue->locked_explicit = false; queue->lock_requests -= 1; // Wakeup mp_dispatch_queue_process(), and maybe other mp_dispatch_lock()s. // (Would be nice to wake up only 1 other locker if lock_requests>0.) pthread_cond_broadcast(&queue->cond); pthread_mutex_unlock(&queue->lock);}