[FFmpeg-devel] [PATCH 1/3] pthread : Remove one unnecessary lock/unlock pair in worker loop.

[Aaron Colwell]

On Thu, Mar 22, 2012 at 10:34 AM, Reimar Döffinger <Reimar.Doeffinger at gmx.de
> wrote:

> On Thu, Mar 22, 2012 at 09:51:49AM -0700, Aaron Colwell wrote:
> > Why does ff_thread_finish_setup(avctx) really need to be called outside
> of
> > the p->mutex?
>
> I doubt it needs to, it just generally is safer to not keep a mutex
> without a good reason to do so, not the other way round of only
> releasing a mutex when you absolutely have to.
>

In general I would agree, but in this case it isn't particularly clear why
p->mutex isn't needed only at this specific point. A few lines down the
same ff_thread_finish_setup() call is made but with p->mutex locked. Any
idea why these calls are made in different locking contexts?

>From what I can tell p->mutex appears to only be used for allowing packets
to be submitted when the worker thread is ready for them. It seems like
this extra unlocked region opens up the possiblity for submit_packet() to
sneak in state modifications when the worker thread isn't really ready. Am
I misunderstanding the role of p->mutex?

Aaron