[vlc-devel] [PATCH] HLS: don't signal dl thread out of the blue in Close()

[Frederic YHUEL]

On Mon, Jun 25, 2012 at 7:08 PM, Hugo Beauzée-Luyssen <hugo at beauzee.fr> wrote:
> On Mon, Jun 25, 2012 at 8:00 PM, Laurent Aimar <fenrir at elivagar.org> wrote:
>> On Mon, Jun 25, 2012 at 07:59:04PM +0300, Hugo Beauzée-Luyssen wrote:
>>> On Mon, Jun 25, 2012 at 10:48 AM, Frederic YHUEL <fyhuel at viotech.net> wrote:
>>> > On Tue, Jun 19, 2012 at 4:17 PM, Frédéric Yhuel <fyhuel at viotech.net> wrote:
>>> >> ---
>>> >>  modules/stream_filter/httplive.c |    5 ++++-
>>> >>  1 file changed, 4 insertions(+), 1 deletion(-)
>>> >>
>>> >> diff --git a/modules/stream_filter/httplive.c b/modules/stream_filter/httplive.c
>>> >> index 5b15bab..5758189 100644
>>> >> --- a/modules/stream_filter/httplive.c
>>> >> +++ b/modules/stream_filter/httplive.c
>>> >> @@ -2000,8 +2000,11 @@ static void Close(vlc_object_t *p_this)
>>> >>
>>> >>     /* */
>>> >>     vlc_mutex_lock(&p_sys->download.lock_wait);
>>> >> -    vlc_cond_signal(&p_sys->download.wait);
>>> >> +    /* negate the condition variable's predicate */
>>> >> +    p_sys->download.segment = p_sys->playback.segment = 0;
>>> >> +    p_sys->download.seek = 0; /* better safe than sorry */
>>> >>     vlc_mutex_unlock(&p_sys->download.lock_wait);
>>> >> +    vlc_cond_signal(&p_sys->download.wait);
>>  I am not sure that a vlc_cond_signal outside the lock is valid.
>>
>
> Indeed, missed that :/
> As far as I know it is "valid", but a bad idea. Will fix the patch locally.
>

Michael Kerrisk writes in "The Linux Programming Interface" that both
are valid, according to SUSv3.

It seems like Butenhof points out that, on some implementations,
unlocking the mutex and then signaling the condition variable yields
to better performance. I don't know if is really true though :-)

The important thing is to change the predicate while the mutex is acquired.


Best regards
Frédéric