[vlc-devel] [PATCH] HLS: remove some useless mutex locks

[Frederic YHUEL]

On Wed, Feb 8, 2012 at 7:42 PM, Rafaël Carré <funman at videolan.org> wrote:
> Le 2012-02-08 03:51, Frederic YHUEL a écrit :
>> On Tue, Feb 7, 2012 at 7:27 PM, Rafaël Carré <funman at videolan.org> wrote:
>>> Le 2012-02-07 11:48, Rémi Denis-Courmont a écrit :
>>>> Le mardi 7 février 2012 18:33:50 Frederic YHUEL, vous avez écrit :
>>>>> Out of the blue?
>>>>
>>>> The critical section does nothing other than signal the condition.
>>>>
>>>>> Do you mean that we should maintain the state (ALIVE | WAITING |
>>>>> TERMINATED ) of the downloading thread in a shared variable, and that
>>>>> we should call vlc_cond_signal() only after having checked the state?
>>>>
>>>> I am referring to the model behind POSIX condition variables, which is the one
>>>> that VLC condition variables follow.
>>>
>>> Check the manpage of pthread_cond_wait it has some explanation.
>>>
>>
>> Thanks Rémi and Rafaël. I guess that since a condition wait is a
>> cancellation point, we just have to send a cancellation request,
>> rigtht?
>
> I don't know what you're trying to do.
>
> If you cancel the thread make sure all its resources are released.
>

Sorry I said rubbish (but it wasn't really me, somebody hacked my
email account to try and ruin my reputation forever)

>>
>> For the second chunk of code, in hls_Read, I guess that the mutex
>> should be acquired sooner, before p_sys->playback.segment is
>> incremented, right?
>
> As soon as the condition (predicate in the manpage) that you're
> signalling is accessed.
>
> Check modules/xdg/inhibit.c , the condition is p_sys->suspend and the
> module takes care of spurious wake ups in pthread_cond_wait with a
> while() loop.
>
>
>  Spurious  wakeups  from   the   pthread_cond_timedwait()   or
>       pthread_cond_wait()    functions    may    occur.   Since   the
>  return   from
>       pthread_cond_timedwait() or pthread_cond_wait() does not imply
> anything  about
>       the  value  of  this  predicate, the predicate should be
> re-evaluated upon such
>       return.
>

Yes, I understood that, and so I suppose my guess is correct.

But I've said too much rubbish on that subject, so I will come back
later, when I have a better understanding of threading.

Thanks for your time!

-- 
Frédéric