/* * 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 <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;    mp_mutex lock;    mp_cond 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;    mp_thread_id in_process_thread_id;    // 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;    mp_thread_id locked_explicit_thread_id;}; 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;    mp_assert(!queue->head);    mp_assert(!queue->in_process);    mp_assert(!queue->lock_requests);    mp_assert(!queue->locked);    mp_cond_destroy(&queue->cond);    mp_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 mp_thread_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);    mp_mutex_init(&queue->lock);    mp_cond_init(&queue->cond);    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. poll(). In the case of poll(),// the wakeup_fn could for example write a byte into a "wakeup" pipe in order// to unblock the poll(). 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){    mp_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);                mp_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.    mp_cond_broadcast(&queue->cond);    // No wakeup callback -> assume mp_dispatch_queue_process() needs to be    // interrupted instead.    if (!queue->wakeup_fn)        queue->interrupted = true;    mp_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){    mp_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;        }    }    mp_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);     mp_mutex_lock(&queue->lock);    while (!item.completed)        mp_cond_wait(&queue->cond, &queue->lock);    mp_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){    mp_mutex_lock(&queue->lock);    queue->wait = timeout > 0 ? mp_time_ns_add(mp_time_ns(), timeout) : 0;    mp_assert(!queue->in_process); // recursion not allowed    queue->in_process = true;    queue->in_process_thread_id = mp_thread_current_id();    // Wake up thread which called mp_dispatch_lock().    if (queue->lock_requests)        mp_cond_broadcast(&queue->cond);    while (1) {        if (queue->lock_requests) {            // Block due to something having called mp_dispatch_lock().            mp_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.            mp_assert(!queue->locked);            queue->locked = true;            mp_mutex_unlock(&queue->lock);             item->fn(item->fn_data);             mp_mutex_lock(&queue->lock);            mp_assert(queue->locked);            queue->locked = false;            // Wakeup mp_dispatch_run(), also mp_dispatch_lock().            mp_cond_broadcast(&queue->cond);            if (item->asynchronous) {                talloc_free(item);            } else {                item->completed = true;            }        } else if (queue->wait > 0 && !queue->interrupted) {            if (mp_cond_timedwait_until(&queue->cond, &queue->lock, queue->wait))                queue->wait = 0;        } else {            break;        }    }    mp_assert(!queue->locked);    queue->in_process = false;    queue->interrupted = false;    mp_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){    mp_mutex_lock(&queue->lock);    queue->interrupted = true;    mp_cond_broadcast(&queue->cond);    mp_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){    mp_mutex_lock(&queue->lock);    if (queue->in_process && queue->wait > until) {        queue->wait = until;        mp_cond_broadcast(&queue->cond);    }    mp_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){    mp_mutex_lock(&queue->lock);    // Must not be called recursively from dispatched callbacks.    if (queue->in_process)        mp_assert(!mp_thread_id_equal(queue->in_process_thread_id, mp_thread_current_id()));    // Must not be called recursively at all.    if (queue->locked_explicit)        mp_assert(!mp_thread_id_equal(queue->locked_explicit_thread_id, mp_thread_current_id()));    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) {        mp_mutex_unlock(&queue->lock);        if (queue->wakeup_fn)            queue->wakeup_fn(queue->wakeup_ctx);        mp_mutex_lock(&queue->lock);        if (queue->in_process)            break;        mp_cond_wait(&queue->cond, &queue->lock);    }    // Wait until we can get the lock.    while (!queue->in_process || queue->locked)        mp_cond_wait(&queue->cond, &queue->lock);    // "Lock".    mp_assert(queue->lock_requests);    mp_assert(!queue->locked);    mp_assert(!queue->locked_explicit);    queue->locked = true;    queue->locked_explicit = true;    queue->locked_explicit_thread_id = mp_thread_current_id();    mp_mutex_unlock(&queue->lock);} // Undo mp_dispatch_lock().void mp_dispatch_unlock(struct mp_dispatch_queue *queue){    mp_mutex_lock(&queue->lock);    mp_assert(queue->locked);    // Must be called after a mp_dispatch_lock(), from the same thread.    mp_assert(queue->locked_explicit);    mp_assert(mp_thread_id_equal(queue->locked_explicit_thread_id, mp_thread_current_id()));    // "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.)    mp_cond_broadcast(&queue->cond);    mp_mutex_unlock(&queue->lock);}