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Date: Tue, 3 Feb 2009 13:09:25 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
       Benjamin Herrenschmidt <benh@kernel.crashing.org>,
       "Rafael J. Wysocki" <rjw@sisk.pl>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Jesse Barnes <jesse.barnes@intel.com>, Andreas Schwab <schwab@suse.de>,
       Len Brown <lenb@kernel.org>
Subject: Re: PCI PM: Restore standard config registers of all devices early
Message-ID: <20090203120925.GA19979@elte.hu>
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* Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:

> On Tue, 2009-02-03 at 06:06 +0100, Ingo Molnar wrote:
> > 
> > Mutexes should work just fine in irqs-off sections - they'll safely 
> > save/restore interrupts, even the debug variants.
> 
> mutex_lock() has might_sleep() which will generate a splat in atomic
> contexts.
> 
> That said, afaik the acpi code uses semaphores.

even the might_sleep() should be OK with Linus's system_state change to the 
suspend code:

void __might_sleep(char *file, int line)
{
#ifdef in_atomic
        static unsigned long prev_jiffy;        /* ratelimiting */

        if ((!in_atomic() && !irqs_disabled()) ||
                    system_state != SYSTEM_RUNNING || oops_in_progress)

	Ingo