[alsa-devel] Is the mixer interface in the kernel protect against concurrent access?

Jaroslav Kysela perex at perex.cz
Mon Dec 17 16:43:01 CET 2007

On Mon, 17 Dec 2007, Hans-Christian Egtvedt wrote:

> Hi,
> I am solving a locking bug in the at73c213 SPI sound driver, and
> wondered if the mixer API is protected against concurrent access in
> ALSA? Or should I implement a mutex to protect my hardware against
> concurrent access?

Control r/w callbacks are protected with a semaphore - 
card->controls_rwsem . See sound/core/control.c for more details. Anyway, 
you need to protect your registers with spinlocks (if required of 


Jaroslav Kysela <perex at perex.cz>
Linux Kernel Sound Maintainer
ALSA Project

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