linux-kernel - Re: [PATCH RFC v1 1/3] ARM: Add irq disabled version of soft

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Date:	Mon, 24 Feb 2014 23:56:30 -0800
From:	Russ Dill <Russ.Dill@...com>
To:	Sebastian Capella <sebastian.capella@...aro.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>
CC:	<linux-kernel@...r.kernel.org>, <linux-pm@...r.kernel.org>,
	<linaro-kernel@...ts.linaro.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Will Deacon <will.deacon@....com>, Robin Holt <holt@....com>
Subject: Re: [PATCH RFC v1 1/3] ARM: Add irq disabled version of soft_restart.

On 02/24/2014 03:13 PM, Sebastian Capella wrote:
> Quoting Russell King - ARM Linux (2014-02-22 02:26:17)
>> On Tue, Feb 18, 2014 at 05:52:07PM -0800, Sebastian Capella wrote:
>>> From: Russ Dill <Russ.Dill@...com>
>>>
>>> This adds the ability to run soft_restart with local_irq/fiq_disable
>>> already called. This is helpful for the hibernation code paths.
>>
>> I'd rather keep this simple.  There's no problem with calling soft_restart
>> with interrupts already disabled.  local_irq_disable()/local_fiq_disable()
>> there should be harmless.
> 
> Hi Russell,
> 
> I'm observing a data abort loop when I replace this call:
> 
> In the local_irq_disable, it ends up calling trace_hardirqs_off
> (CONFIG_TRACE_IRQFLAGS_SUPPORT is enabled), which calls
> trace_hardirqs_off_caller which checks lockdep_recursion in the
> current task, but we've switched to a temporary stack with the
> call_with_stack, and get_current is returning NULL.  This
> triggers a data abort, which calls trace_hardirqs_off
> again and so on.
> 
> Do you have any suggestions here?
> 
> Thanks,
> 
> Sebastian
> 

So the alternative is to have a version of the call that calls a special
no trace version of local_irq_disable()/local_fiq_disable(). Which would
be preferable? Having a noirq version of soft_restart seems much simpler
to me.
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