diff mbox series

[FFmpeg-devel] avcodec/videotoolboxenc: move pthread_cond_signal after add buffer to the queue

Message ID 20200828011302.78140-1-lq@chinaffmpeg.org
State Accepted
Commit 9837f5a64322e89f825a99f14c1a0d27b17b183c
Headers show
Series [FFmpeg-devel] avcodec/videotoolboxenc: move pthread_cond_signal after add buffer to the queue
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Commit Message

Steven Liu Aug. 28, 2020, 1:13 a.m. UTC
From: Tian Qi <tianqi@kuaishou.com>

In the VT encoding insertion by FFmpeg,
and vtenc_q_push is callback to add the encoded data
to the singly linked list group in VTEncContext,
and consumers are notified to fetch it.
However, because it first informs consumers of pthread_cond_signal,
and then inserts the data into the tail,
there is a multi-thread safety hazard.

Signed-off-by: Steven Liu <lq@chinaffmpeg.org>
---
 libavcodec/videotoolboxenc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

zhilizhao(赵志立) Aug. 27, 2020, 3 p.m. UTC | #1
> On Aug 28, 2020, at 9:13 AM, Steven Liu <lq@chinaffmpeg.org> wrote:
> 
> From: Tian Qi <tianqi@kuaishou.com>
> 
> In the VT encoding insertion by FFmpeg,
> and vtenc_q_push is callback to add the encoded data
> to the singly linked list group in VTEncContext,
> and consumers are notified to fetch it.
> However, because it first informs consumers of pthread_cond_signal,
> and then inserts the data into the tail,
> there is a multi-thread safety hazard.

The patch makes the code more logical, although it’s not a real issue. So LGTM.

> 
> Signed-off-by: Steven Liu <lq@chinaffmpeg.org>
> ---
> libavcodec/videotoolboxenc.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/libavcodec/videotoolboxenc.c b/libavcodec/videotoolboxenc.c
> index e89cfaeed8..62ed86fc04 100644
> --- a/libavcodec/videotoolboxenc.c
> +++ b/libavcodec/videotoolboxenc.c
> @@ -338,7 +338,6 @@ static void vtenc_q_push(VTEncContext *vtctx, CMSampleBufferRef buffer, ExtraSEI
>     info->next = NULL;
> 
>     pthread_mutex_lock(&vtctx->lock);
> -    pthread_cond_signal(&vtctx->cv_sample_sent);
> 
>     if (!vtctx->q_head) {
>         vtctx->q_head = info;
> @@ -348,6 +347,7 @@ static void vtenc_q_push(VTEncContext *vtctx, CMSampleBufferRef buffer, ExtraSEI
> 
>     vtctx->q_tail = info;
> 
> +    pthread_cond_signal(&vtctx->cv_sample_sent);
>     pthread_mutex_unlock(&vtctx->lock);
> }
> 
> -- 
> 2.25.0
> 
> 
> 
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> 
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diff mbox series

Patch

diff --git a/libavcodec/videotoolboxenc.c b/libavcodec/videotoolboxenc.c
index e89cfaeed8..62ed86fc04 100644
--- a/libavcodec/videotoolboxenc.c
+++ b/libavcodec/videotoolboxenc.c
@@ -338,7 +338,6 @@  static void vtenc_q_push(VTEncContext *vtctx, CMSampleBufferRef buffer, ExtraSEI
     info->next = NULL;
 
     pthread_mutex_lock(&vtctx->lock);
-    pthread_cond_signal(&vtctx->cv_sample_sent);
 
     if (!vtctx->q_head) {
         vtctx->q_head = info;
@@ -348,6 +347,7 @@  static void vtenc_q_push(VTEncContext *vtctx, CMSampleBufferRef buffer, ExtraSEI
 
     vtctx->q_tail = info;
 
+    pthread_cond_signal(&vtctx->cv_sample_sent);
     pthread_mutex_unlock(&vtctx->lock);
 }