Re: [PATCH] dmaengine: cppi41: Fix oops in cppi41_runtime_resume

[Tony Lindgren <tony-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org>]

* Grygorii Strashko <grygorii.strashko-l0cyMroinI0@public.gmane.org> [170112 13:54]:
> On 01/12/2017 03:30 PM, Tony Lindgren wrote:
>
> Sry, but even if it looks better it might still race with PM runtime :(
> 
> > -	if (likely(pm_runtime_active(cdd->ddev.dev)))
> > +	if (likely(atomic_read(&cdd->active)))
> >  		push_desc_queue(c);
> >  	else
> 
> 
> - CPU is here (-EINPROGRESS and active == 0) and then preempted 
> - PM runtime will finish cppi41_runtime_resume and clean-up pending descs
> - CPU return here and adds desc to the pending queue
> - oops
> 
> Am I wrong?

We had cppi41_dma_issue_pending() getting called from atomic contex and
cppi41_runtime_resume() getting preempted where cppi41_dma_issue_pending()
would add to the queue.

If what you're saying can happen in some cases, then we again see the
WARN_ON(!list_empty(&cdd->pending)) in cppi41_runtime_suspend(). At least
so far I have no longer been able to make happen today.

Regards,

Tony
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