[vlc-devel] [PATCH] input: reduce the number of locks for every MainLoop cycle

[Hugo Beauzée-Luyssen]

On 12/11/2015 11:36 AM, Steve Lhomme wrote:
> ---
>   src/input/input.c          | 7 +------
>   src/input/input_internal.h | 2 +-
>   2 files changed, 2 insertions(+), 7 deletions(-)
>
> diff --git a/src/input/input.c b/src/input/input.c
> index a5d408c..a982fa7 100644
> --- a/src/input/input.c
> +++ b/src/input/input.c
> @@ -510,12 +510,7 @@ static void *Preparse( void *obj )
>   bool input_Stopped( input_thread_t *input )
>   {
>       input_thread_private_t *sys = input->p;
> -    bool ret;
> -
> -    vlc_mutex_lock( &sys->lock_control );
> -    ret = sys->is_stopped;
> -    vlc_mutex_unlock( &sys->lock_control );
> -    return ret;
> +    return sys->is_stopped;
>   }
>
>   /*****************************************************************************
> diff --git a/src/input/input_internal.h b/src/input/input_internal.h
> index 249ef2e..1d35d94 100644
> --- a/src/input/input_internal.h
> +++ b/src/input/input_internal.h
> @@ -89,7 +89,7 @@ struct input_thread_private_t
>       /* Current state */
>       int         i_state;
>       bool        is_running;
> -    bool        is_stopped;
> +    atomic_bool is_stopped;
>       bool        b_recording;
>       int         i_rate;
>
>
That doesn't look good. You need to atomic_store/atomic_load this value.
atomic_bool is defined as such:
typedef          bool      atomic_bool;

meaning if you don't atomic_* it, you'll lose all the synchronization, 
and will enter the realm of undefined behavior.

Regards,