Commit c5380868 authored by Rémi Denis-Courmont's avatar Rémi Denis-Courmont

Work-around window-on-top + fullscreen deadlock (refs #882)

FIXME FIXME FIXME FIXME: EXPLICIT HACK.
On the one hand, we cannot hold the lock while triggering a callback, as
it causes a deadlock with video-on-top handling. On the other hand, we
have to lock while triggering the callback to:
 1/ make sure video-on-top remains in sync with fullscreen (i.e.
    unlocking creates a race condition if fullscreen is switched on and
    off VERY FAST).
 2/ avoid possible corruption bugs if another thread gets the mutex and
    modifies our data in-between (though it does not seem like it could really
    do much harm in this particular case).

This is obviously contradictory. Correct solutions may include:
 - putting the fullscreen NAND video-on-top logic out of libvlc,
   back into the video output plugins (ugly code duplication...),
 - serializing fullscreen and video-on-top handling properly instead of
   using the fullscreen callback. That's got to be the correct one.
parent 4b8daf87
...@@ -1326,8 +1326,38 @@ static int ManageVideo( vout_thread_t *p_vout ) ...@@ -1326,8 +1326,38 @@ static int ManageVideo( vout_thread_t *p_vout )
/* Update the object variable and trigger callback */ /* Update the object variable and trigger callback */
val.b_bool = !p_vout->b_fullscreen; val.b_bool = !p_vout->b_fullscreen;
/*
* FIXME FIXME FIXME FIXME: EXPLICIT HACK.
* On the one hand, we cannot hold the lock while triggering a
* callback, as it causes a deadlock with video-on-top handling.
* On the other hand, we have to lock while triggering the
* callback to:
* 1/ make sure video-on-top remains in sync with fullscreen
* (i.e. unlocking creates a race condition if fullscreen is
* switched on and off VERY FAST).
* 2/ avoid possible corruption bugs if another thread gets the
* mutex and modifies our data in-between.
*
* This is obviously contradictory. Correct solutions may include:
* - putting the fullscreen NAND video-on-top logic out of libvlc,
* back into the video output plugins (ugly code duplication...),
* - serializing fullscreen and video-on-top handling properly
* instead of doing it via the fullscreen callback. That's got to
* be the correct one.
*/
#ifdef MODULE_NAME_IS_xvmc
xvmc_context_reader_unlock( &p_vout->p_sys->xvmc_lock );
#endif
vlc_mutex_unlock( &p_vout->p_sys->lock );
var_Set( p_vout, "fullscreen", val ); var_Set( p_vout, "fullscreen", val );
vlc_mutex_lock( &p_vout->p_sys->lock );
#ifdef MODULE_NAME_IS_xvmc
xvmc_context_reader_lock( &p_vout->p_sys->xvmc_lock );
#endif
ToggleFullScreen( p_vout ); ToggleFullScreen( p_vout );
p_vout->i_changes &= ~VOUT_FULLSCREEN_CHANGE; p_vout->i_changes &= ~VOUT_FULLSCREEN_CHANGE;
} }
......
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