From 5152196b2b47d446d9a509b9bfb318daa26a1f2b Mon Sep 17 00:00:00 2001 From: Ben Jackson Date: Fri, 18 Oct 2013 15:28:50 +0100 Subject: [PATCH] pthread: Avoid spurious wakeups pthread_wait_cond can wake up unexpectedly (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. Test both cases to ensure the wakeup is real. Signed-off-by: Ben Jackson Signed-off-by: Michael Niedermayer Signed-off-by: Derek Buitenhuis Signed-off-by: Luca Barbato --- libavcodec/pthread.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/libavcodec/pthread.c b/libavcodec/pthread.c index b0d9e27aa9..b646f66ab1 100644 --- a/libavcodec/pthread.c +++ b/libavcodec/pthread.c @@ -61,6 +61,7 @@ typedef struct ThreadContext { pthread_cond_t last_job_cond; pthread_cond_t current_job_cond; pthread_mutex_t current_job_lock; + unsigned current_execute; int current_job; int done; } ThreadContext; @@ -141,6 +142,7 @@ static void* attribute_align_arg worker(void *v) { AVCodecContext *avctx = v; ThreadContext *c = avctx->thread_opaque; + unsigned last_execute = 0; int our_job = c->job_count; int thread_count = avctx->thread_count; int self_id; @@ -152,8 +154,9 @@ static void* attribute_align_arg worker(void *v) if (c->current_job == thread_count + c->job_count) pthread_cond_signal(&c->last_job_cond); - if (!c->done) + 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) { @@ -173,7 +176,8 @@ 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); } @@ -222,6 +226,7 @@ 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);