[FFmpeg-devel] [PATCH 1/3] avutil/log: add AV_LOG_ASYNC

[anshul]

On 03/20/2014 11:54 AM, wm4 wrote:
> On Thu, 20 Mar 2014 03:57:57 +0100
> Michael Niedermayer <michaelni at gmx.at> wrote:
>
>
>> +/**
>> + * Do not thread synchronization.
>> + * This allows av_log() to be used from a signal handler but may lead to
>> + * garbled output.
>> + */
>> +#define AV_LOG_ASYNC 0x1000
>>   void av_log_set_flags(int arg);
Is there any special reason for value 0x1000
Why not 0x0002 or 0x0100?

As per my understanding ASYNC and SKIP_REPEATED both flag change 
properties of log mechanism.
so both should have similar numbering otherwise more properties related 
flag would result in chaos.

Since your changes are related to deadlock condition when same thread 
apply lock twice, there may be better
approach if we check pthread_self().

Some comments from manual of pthread_mutex_lock
        The mutex functions and the particular default settings of the 
mutex attributes have been motivated by the desire to not preclude  
fast,  inlined
        implementations of mutex locking and unlocking.

        For  example, deadlocking on a double-lock is explicitly allowed 
behavior in order to avoid requiring more overhead in the basic 
mechanism than is
        absolutely necessary. (More "friendly" mutexes that detect 
deadlock or that allow multiple locking by the same thread are easily  
constructed  by
        the  user via the other mechanisms provided. For example, 
pthread_self() can be used to record mutex ownership.) Implementations 
might also choose
        to provide such extended features as options via special mutex 
attributes.
> Just for ffmpeg.c? Please no...
This would help other application too, it is just now used in ffmpeg.c 
will take time to adapt this feature by other application.
So yes

Thanks
Anshul