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pthread: Avoid crashes/odd behavior caused by spurious wakeups

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pthread_wait_cond can wake up for no reason (Wikipedia: Spurious_wakeup).
The FF_THREAD_SLICE thread mechanism could spontaneously execute jobs or
allow the caller of avctx->execute to return before all jobs were complete.
This adds tests to both cases to ensure the wakeup is real.

Signed-off-by: Ben Jackson <ben@ben.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
This commit is contained in:
Ben Jackson 2012-09-13 21:26:43 -07:00 committed by Michael Niedermayer
parent 93b240f4a5
commit e3329474a3
1 changed files with 8 additions and 2 deletions
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10
libavcodec/pthread.c
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@ -80,6 +80,7 @@ typedef struct ThreadContext {
pthread_cond_t current_job_cond;
pthread_mutex_t current_job_lock;
int current_job;
unsigned int current_execute;
int done;
} ThreadContext;
@ -204,6 +205,7 @@ static void* attribute_align_arg worker(void *v)
AVCodecContext *avctx = v;
ThreadContext *c = avctx->thread_opaque;
int our_job = c->job_count;
int last_execute = 0;
int thread_count = avctx->thread_count;
int self_id;
@ -214,7 +216,9 @@ static void* attribute_align_arg worker(void *v)
if (c->current_job == thread_count + c->job_count)
pthread_cond_signal(&c->last_job_cond);
pthread_cond_wait(&c->current_job_cond, &c->current_job_lock);
while (last_execute == c->current_execute && !c->done)
pthread_cond_wait(&c->current_job_cond, &c->current_job_lock);
last_execute = c->current_execute;
our_job = self_id;
if (c->done) {
@ -234,7 +238,8 @@ static void* attribute_align_arg worker(void *v)
static av_always_inline void avcodec_thread_park_workers(ThreadContext *c, int thread_count)
{
pthread_cond_wait(&c->last_job_cond, &c->current_job_lock);
while (c->current_job != thread_count + c->job_count)
pthread_cond_wait(&c->last_job_cond, &c->current_job_lock);
pthread_mutex_unlock(&c->current_job_lock);
}
@ -283,6 +288,7 @@ static int avcodec_thread_execute(AVCodecContext *avctx, action_func* func, void
c->rets = &dummy_ret;
c->rets_count = 1;
}
c->current_execute++;
pthread_cond_broadcast(&c->current_job_cond);
avcodec_thread_park_workers(c, avctx->thread_count);