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avcodec/executor: remove unused ready callback 

Due to the nature of multithreading, using a "ready check" mechanism may introduce a deadlock. For example:

Suppose all tasks have been submitted to the executor, and the last thread checks the entire list and finds
no ready tasks. It then goes to sleep, waiting for a new task. However, for some multithreading-related reason,
a task becomes ready after the check. Since no other thread is aware of this and no new tasks are being added to
the executor, a deadlock occurs.

In VVC, this function is unnecessary because we use a scoreboard. All tasks submitted to the executor are ready tasks.
This commit is contained in:
Nuo Mi 2024-09-24 22:16:57 +08:00
parent 8446e27bf3
commit 40a14ef970
3 changed files with 2 additions and 15 deletions
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6
libavcodec/executor.c
View File

@ -79,10 +79,8 @@ static void add_task(FFTask **prev, FFTask *t)
static int run_one_task(FFExecutor *e, void *lc)
{
FFTaskCallbacks *cb = &e->cb;
FFTask **prev;
FFTask **prev = &e->tasks;
for (prev = &e->tasks; *prev && !cb->ready(*prev, cb->user_data); prev = &(*prev)->next)
/* nothing */;
if (*prev) {
FFTask *t = remove_task(prev, *prev);
if (e->thread_count > 0)
@ -143,7 +141,7 @@ FFExecutor* ff_executor_alloc(const FFTaskCallbacks *cb, int thread_count)
{
FFExecutor *e;
int has_lock = 0, has_cond = 0;
if (!cb || !cb->user_data || !cb->ready || !cb->run || !cb->priority_higher)
if (!cb || !cb->user_data || !cb->run || !cb->priority_higher)
return NULL;
e = av_mallocz(sizeof(*e));

3
libavcodec/executor.h
View File

@ -42,9 +42,6 @@ typedef struct FFTaskCallbacks {
// return 1 if a's priority > b's priority
int (*priority_higher)(const FFTask *a, const FFTask *b);
// task is ready for run
int (*ready)(const FFTask *t, void *user_data);
// run the task
int (*run)(FFTask *t, void *local_context, void *user_data);
} FFTaskCallbacks;

8
libavcodec/vvc/thread.c
View File

@ -372,13 +372,6 @@ static int task_is_stage_ready(VVCTask *t, int add)
return task_has_target_score(t, stage, score);
}
static int task_ready(const FFTask *_t, void *user_data)
{
VVCTask *t = (VVCTask*)_t;
return task_is_stage_ready(t, 0);
}
#define CHECK(a, b) \
do { \
if ((a) != (b)) \
@ -689,7 +682,6 @@ FFExecutor* ff_vvc_executor_alloc(VVCContext *s, const int thread_count)
s,
sizeof(VVCLocalContext),
task_priority_higher,
task_ready,
task_run,
};
return ff_executor_alloc(&callbacks, thread_count);