linux-kernel - Re: try_to_freeze() called with IRQs disabled on ARM

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Message-ID: <20110825122543.GC8883@n2100.arm.linux.org.uk>
Date:	Thu, 25 Aug 2011 13:25:43 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Tejun Heo <tj@...nel.org>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: try_to_freeze() called with IRQs disabled on ARM

On Thu, Aug 25, 2011 at 02:17:10PM +0200, Tejun Heo wrote:
> Hello, Russell.
> 
> On Thu, Aug 25, 2011 at 01:14:16PM +0100, Russell King - ARM Linux wrote:
> > was introduced, every other architecture should have been updated for
> > that change...  So this call in the ARM signal handling code to
> > try_to_freeze() should just be deleted as it should've been done five
> > years ago.
> 
> I agree.  I don't think it's necessary there, so for now, let's just
> delete that call, but get_signal_to_deliver() expects to be called
> with IRQ enabled so it would still be a good idea to turn on/off IRQs
> explicitly around it.

No.  Stop bodging and hiding problems.  Anywhere which does this:

	local_irq_enable();
	do something
	local_irq_disable();

is a bug.  Things are called with IRQs disabled for a reason - randomly
re-enabling IRQs does not "fix" stuff, it merely introduces subtle bugs
while hiding warnings of those bugs.

Please go back and read my response to Mark at the beginning of this
thread, where I describe why IRQs are disabled here.

The only solution here is to fix the problem properly, and I'm working
on a patch to fix the problem I highlighted in my earlier response to
Mark.  Once we have that problem fixed, we can then (more) safely call
do_signal() with IRQs enabled.
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