[vlc-devel] Warning: callback deadlocks (was Re: vlc: svn commit r18744 (dionoea))

Rémi Denis-Courmont rem at videolan.org
Sat Feb 10 09:15:51 CET 2007

Le samedi 10 février 2007 01:51, Subversion daemon a écrit :
> r18744 | dionoea | 2007-02-10 00:51:34 +0100 (Sat, 10 Feb 2007) | 2
> lines Changed paths:
>    M /trunk/modules/control/rc.c
> Add "key" (or "hotkey") command in RC to simulate a hotkey press.
> Original idea by artois_val on the forum (
> http://forum.videolan.org/viewtopic.php?t=31646 ).

Whether this applies here or not, I do not know, but triggering 
hotkey/action is an easy way to trigger a deadlock. Essentially, if you 
trigger kotheys, the safe solution is not to have any variables 
callback yourself, or not use ANY lock/condition in any callback. Note 
that reading/writing VLC variables does use locking, and should hence 
be banned from callbacks.

This sucks big time (and probably many plugins do not respect this 
rule), but there is not much solution.

One such annoying deadlock currently exists in the fullscreen and 
always-on-top handling between video output core and X11 plugin (and 
possibly other video outputs), and the current work around is rather 

Rémi Denis-Courmont
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