>> I have not been able to figure out when you need >> a) the pcm_mutex only >> b) the fe stream lock only >> c) both pcm_mutex and fe stream lock > > The pcm_mutex is needed for every sleepable function that treat DPCM > FE link, but the mutex is taken only at the upper level, i.e. the > top-most caller like PCM ops FE itself or the DAPM calls. > > That said, pcm_mutex is the top-most protection of BE links in FE. > But, there is a code path where a mutex can't be used, and that's the > FE and BE trigger. For protecting against this, the FE stream lock is > taken only at the placing both adding and deleting a BE *in addition*. > At those places, both pcm_mutex and FE stream lock are taken. > > BE stream lock is taken in addition below the above mutex and FE > locks. Thanks Takashi, now I get the idea. Makes sense indeed. I'll make sure to add this explanation to the commit message/cover so that it's not lost. I added your three patches to my tests, so far so good, code is that https://github.com/thesofproject/linux/pull/3215 Thanks and have a nice week-end. -Pierre
