[FFmpeg-devel] [PATCH] pthread_frame: make accesses to debug field be protected by owner lock.

Ronald S. Bultje rsbultje at gmail.com
Thu Jul 6 05:24:48 EEST 2017

Hi Wan-Teh,

On Wed, Jul 5, 2017 at 8:08 PM, Wan-Teh Chang <wtc at google.com> wrote:

> Hi Ronald,
> On Wed, Jul 5, 2017 at 3:31 PM, Ronald S. Bultje <rsbultje at gmail.com>
> wrote:
> > Hi Wan-Teh,
> >
> > On Wed, Jul 5, 2017 at 6:12 PM, Wan-Teh Chang <wtc at google.com> wrote:
> >>
> >> Thank you for all the tsan warning fixes. In the meantime, it would be
> >> good to revert 2e664b9c1e73c80aab91070c1eb7676f04bdd12d to avoid
> >> confusion.
> >
> >
> > Why? I believe it fixes a subset of the issue.
> Could you explain why it fixes a subset of the issue?

>From what I remember, I was (before this patch) semi-reliably able to
reproduce the issue locally, and it went away after. I've observed the same
thing in the relevant fate station, where before the patch, this warning
occurred semi-reliably in 3-4 tests per run, and after the patch it
sometimes occurs in 1 test per run. I understand this doesn't satisfy you
but I currently don't want to dig through the code to figure out why I
thought this was a good idea, I have other things that take priority.
Reverting the patch will require me to dig through this code also, and I
really don't see the gain.

Some more thoughts:
- I don't think we want to grab a second lock for something trivial like
this (e.g. grabbing progress_mutex when copying the debug field in
- making the debug flags field atomic will be difficult because it's public
API, and I don't think we're ready to expose C11 types in our public API;
- I suppose you could make a private (inside PerThreadContext, which allows
it to be atomic) copy of debug intended for cross-threading purposes and
use that here.


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