Re: [FFmpeg-devel] [PATCH] avutil/executor: Fix missing check before using mutex

[Nuo Mi <nuomi2021@gmail.com>]

On Mon, Jul 1, 2024 at 10:00 PM Zhao Zhili <quinkblack@foxmail.com> wrote:

>
>
> > On Jul 1, 2024, at 21:14, Nuo Mi <nuomi2021@gmail.com> wrote:
> >
> > On Sun, Jun 30, 2024 at 6:45 PM Zhao Zhili <quinkblack@foxmail.com>
> wrote:
> >
> >> From: Zhao Zhili <zhilizhao@tencent.com>
> >>
> >> ---
> >> The code can be simplified by always creating mutex/cond. I'm not sure
> >> it worth the overhead. Please note !HAVE_THREADS don't have the same
> >> problem since it has mock implementation of ff_mutex_lock/unlock.
> >>
> > Hi Zhili,
> > Thank you for the patch.
> > Do we really need this? The lock/unlock/signal functions will return an
> > error if the lock and condition variables are not initialized.
>
> We have strict check in libavutil/thread.h, e.g.,
>
> static inline int strict_pthread_mutex_lock(pthread_mutex_t *mutex)
> {
>     ASSERT_PTHREAD(pthread_mutex_lock, mutex);
> }
>
> The strict check is enabled when configure --assert-level=2.
>
LGTM.
Thank you.

>
> >
> >>
> >> libavutil/executor.c | 9 ++++++---
> >> 1 file changed, 6 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/libavutil/executor.c b/libavutil/executor.c
> >> index fb20104b58..89058fab2f 100644
> >> --- a/libavutil/executor.c
> >> +++ b/libavutil/executor.c
> >> @@ -194,14 +194,17 @@ void av_executor_execute(AVExecutor *e, AVTask *t)
> >>     AVTaskCallbacks *cb = &e->cb;
> >>     AVTask **prev;
> >>
> >> -    ff_mutex_lock(&e->lock);
> >> +    if (e->thread_count)
> >> +        ff_mutex_lock(&e->lock);
> >>     if (t) {
> >>         for (prev = &e->tasks; *prev && cb->priority_higher(*prev, t);
> >> prev = &(*prev)->next)
> >>             /* nothing */;
> >>         add_task(prev, t);
> >>     }
> >> -    ff_cond_signal(&e->cond);
> >> -    ff_mutex_unlock(&e->lock);
> >> +    if (e->thread_count) {
> >> +        ff_cond_signal(&e->cond);
> >> +        ff_mutex_unlock(&e->lock);
> >> +    }
> >>
> >>     if (!e->thread_count || !HAVE_THREADS) {
> >>         // We are running in a single-threaded environment, so we must
> >> handle all tasks ourselves
> >> --
> >> 2.42.0
> >>
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> >>
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> >>
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