On Fri, Mar 20, 2020 at 12:52:03PM +0100, Guennadi Liakhovetski wrote: > On Fri, Mar 13, 2020 at 02:39:56PM +0000, Mark Brown wrote: > > On Thu, Mar 12, 2020 at 03:44:21PM +0100, Guennadi Liakhovetski wrote: > > > #endif > > > + atomic_set(&sdev->reset_count, 0); > > > dev_set_drvdata(dev, sdev); > > Do we really need to use atomics for this? They are hard to use > > correctly. > This variable is accessed from 2 contexts: it's incremented by the SOF > driver, when the firmware has booted and it's read by the SOF > VirtIO backend vhost-be.c when receiving a resume request from the guest. > Timewise the variable will only be incremented during the DSP resume / > power up, while the VirtIO back end is waiting for the resume to complete in > pm_runtime_get_sync(). And only after that it reads the variable. But that > can happen on different CPUs. Whereas I think that runtime PM will sync > caches somewhere during the process, I think it is better to access the > variable in an SMP-safe way, e.g. using atomic operations. That doesn't address my concern - to repeat, my concern is that atomics are hard to use correctly. Is there no other concurrency primitive (for example this sounds like a completion) which can be used?
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