On Fri, Jul 03, 2015 at 12:56:53PM +0200, Lars-Peter Clausen wrote: > 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 How to check " all scheduled complete callbacks have finished"? One concern is if add wait in snd_dmaengine_pcm_close(), which wil cause the snd_pcm_release is bound with dmaengine, when there is error in dma and no callback be called. Then the snd_pcm_release will not be released. Best regards wang shengjiu -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
