Module: libav
Branch: master
Commit: 5152196b2b47d446d9a509b9bfb318daa26a1f2b
Author: Ben Jackson <b...@ben.com>
Committer: Luca Barbato <lu_z...@gentoo.org>
Date: Fri Oct 18 15:28:50 2013 +0100
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 <b...@ben.com>
Signed-off-by: Michael Niedermayer <michae...@gmx.at>
Signed-off-by: Derek Buitenhuis <derek.buitenh...@gmail.com>
Signed-off-by: Luca Barbato <lu_z...@gentoo.org>
---
libavcodec/pthread.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/libavcodec/pthread.c b/libavcodec/pthread.c
index b0d9e27..b646f66 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);
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