linux-kernel - Re: Warning during suspend with MS-7310 mainboard

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Message-Id: <200908031604.42857.rusty@rustcorp.com.au>
Date:	Mon, 3 Aug 2009 16:04:41 +0930
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Dave Jones <davej@...hat.com>
Cc:	"Langsdorf, Mark" <mark.langsdorf@....com>,
	Eric Sesterhenn <eric.sesterhenn@...xperts.de>,
	linux-kernel@...r.kernel.org, cpufreq@...r.kernel.org
Subject: Re: Warning during suspend with MS-7310 mainboard

On Fri, 31 Jul 2009 08:47:02 am Dave Jones wrote:
> On Fri, Jul 31, 2009 at 08:37:22AM +0930, Rusty Russell wrote:
>  > Yeah, I was confused: my patch changed set_cpus_allowed_ptr() to
>  > an smp_call_function.  If the latter is a bad idea with irqs disabled, the
>  > former certainly was...
> 
> Right, the only reason reverting your change 'fixes' the problem is
> that we don't have a BUG() in set_cpus_allowed_ptr to check for interrupts
> being disabled.

Exactly.

> hmm, does adding an equivalent check make sense?
> cpufreq seemed to cope just fine when we used set_cpus_allowed_ptr,
> but we might have just got lucky. As we were suspending in this path,
> interaction from the scheduler is minimal. Other callers might not
> be so lucky?

If someone who knows the code can verify that, in fact, we are always on the
right CPU, we can eliminate it altogether.

I'm not happy with a "probably get lucky" scenario...
Rusty.
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