linux-kernel - Re: [RESEND PATCH] ARM: fix 'unannotated irqs-on' lockdep warning

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Date:	Sun, 23 May 2010 23:07:50 +0800
From:	Ming Lei <tom.leiming@...il.com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	linux-arm-kernel@...ts.infradead.org,
	linux-embedded@...r.kernel.org, a.p.zijlstra@...llo.nl,
	linux-kernel@...r.kernel.org
Subject: Re: [RESEND PATCH] ARM: fix 'unannotated irqs-on' lockdep warning

2010/5/23 Russell King - ARM Linux <linux@....linux.org.uk>:
> On Sun, May 23, 2010 at 09:44:20PM +0800, Ming Lei wrote:
>> 2010/5/23 Russell King - ARM Linux <linux@....linux.org.uk>:
>> >>  ENTRY(ret_to_user)
>> >>  ret_slow_syscall:
>> >> -     disable_irq                             @ disable interrupts
>> >> +     disable_irq_notrace                             @ disable interrupts
>> >
>> > I think this one does need to be traced - the pending work functions are
>> > all C code which could call back into lockdep.
>>
>> If there are pending works, schedule will be called to give cpu to it,
>> I wonder why the work function to be scheduled will be run with irq
>> disabled. Seems we should enable irq again before calling schedule,
>> not sure.
>
> No.  I'm talking about things like do_notify_resume().
>
> I think the above should be left as-is, so that as far as lockdep is
> concerned, IRQs are off while userspace runs.  What happens between
> returning to userspace and re-entering the kernel has no bearing what
> so ever on lockdep.
>

Oh, trace_ret_hardirqs_on has to be added before returning to user-space to
remove the warning, like x86 and mips. If you agree, I'd like to post
a new version
patch.

Thanks,

-- 
Lei Ming
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