[FFmpeg-cvslog] pthread: Avoid crashes/odd behavior caused by spurious wakeups
Ben Jackson
git at videolan.org
Sat Sep 15 01:57:29 CEST 2012
ffmpeg | branch: release/0.11 | Ben Jackson <ben at ben.com> | Thu Sep 13 21:26:43 2012 -0700| [f1ec792ae3011531d47070144b8c91d58bb3e76f] | committer: Michael Niedermayer
pthread: Avoid crashes/odd behavior caused by spurious wakeups
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 at ben.com>
Signed-off-by: Michael Niedermayer <michaelni at gmx.at>
(cherry picked from commit e3329474a366de066b25e86f35f5abf9c5a4b7b2)
Signed-off-by: Michael Niedermayer <michaelni at gmx.at>
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=f1ec792ae3011531d47070144b8c91d58bb3e76f
---
libavcodec/pthread.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/libavcodec/pthread.c b/libavcodec/pthread.c
index 482c845..d0d1343 100644
--- a/libavcodec/pthread.c
+++ b/libavcodec/pthread.c
@@ -79,6 +79,7 @@ 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;
@@ -203,6 +204,7 @@ 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;
@@ -213,7 +215,9 @@ 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) {
@@ -233,7 +237,8 @@ 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);
}
@@ -282,6 +287,7 @@ 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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