On 07/03/2015 10:25 AM, Shengjiu Wang wrote:
Hi alsa-devel
There maybe a issue in ALSA when dma complete race with snd_pcm_release.
The pcm release and dma complete are in different thread. There is occasion
that dmaengine_pcm_dma_complete() is called too late, some memory has been
freed, the prtd is null. Then there is kernel dump.
Is there any solution for this issue? Thanks.
We need to introduce a synchronization primitive that allows a dmaengine
client to synchronize to the execution of the complete callbacks.
terminate_all() unfortunately can't do this since terminate_all() might be
called from within one of the complete callbacks and so would cause a
deadlock if we'd wait for all complete callbacks to finish before
terminate_all() returns.
So what is needed is a new function called dmaengine_sync() that will wait
until all scheduled complete callbacks have finished. A call to this
function needs to be put in snd_dmaengine_pcm_close() before the prtd is closed.
- Lars
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