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

Hans-Christian Egtvedt hcegtvedt at atmel.no
Mon Dec 17 17:07:56 CET 2007

On Mon, 2007-12-17 at 16:43 +0100, Jaroslav Kysela wrote:
> On Mon, 17 Dec 2007, Hans-Christian Egtvedt wrote: 
> > 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 
> course).

Thanks for the feedback. I settled upon a mutex since the SPI driver can
not use spinlocks due to a might sleepy spi_sync function call.

Hans-Christian Egtvedt

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