linux-kernel - Re: freezer: should barriers be smp ?

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Message-Id: <201104132258.17705.rjw@sisk.pl>
Date:	Wed, 13 Apr 2011 22:58:17 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Mike Frysinger <vapier@...too.org>
Cc:	Pavel Machek <pavel@....cz>, linux-kernel@...r.kernel.org,
	uclinux-dist-devel@...ckfin.uclinux.org,
	linux-pm@...ts.linux-foundation.org
Subject: Re: freezer: should barriers be smp ?

On Wednesday, April 13, 2011, Mike Frysinger wrote:
> when we suspend/resume Blackfin SMP systems, we notice that the
> freezer code runs on multiple cores.  this is of course what you want
> -- freeze processes in parallel.  however, the code only uses non-smp
> based barriers which causes us problems ... our cores need software
> support to keep caches in sync, so our smp barriers do just that.  but
> the non-smp barriers do not, and so the frozen/thawed processes
> randomly get stuck in the wrong task state.
> 
> thinking about it, shouldnt the freezer code be using smp barriers ?

Yes, it should, but rmb() and wmb() are supposed to be SMP barriers.

Or do you mean something different?

Rafael
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