linux-kernel - Re: [PATCH -V2] acpi: don't cond

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Date:	Thu, 10 Dec 2009 15:21:06 +0300
From:	Alexey Starikovskiy <astarikovskiy@...e.de>
To:	Xiaotian Feng <dfeng@...hat.com>
CC:	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	Len Brown <lenb@...nel.org>,
	Bob Moore <robert.moore@...el.com>,
	Lin Ming <ming.m.lin@...el.com>, Pavel Machek <pavel@....cz>
Subject: Re: [PATCH -V2] acpi: don't cond_resched if irq is disabled

Hi Xiaotian,

I think, this is another round of "armor vs. bullet" race... It will hold until
might_sleep() logic changes again.

Please consider using preemptible() -- IMHO this is the check we should perform 
in our case of voluntary preemption.

Regards,
Alex.


Xiaotian Feng пишет:
> commit 8bd108d adds preemption point after each opcode parse, then
> a sleeping function called from invalid context bug was founded
> during suspend/resume stage. this was fixed in commit abe1dfa by
> don't cond_resched when irq_disabled. But recent commit 138d156 changes
> the behaviour to don't cond_resched when in_atomic. This makes the
> sleeping function called from invalid context bug happen again, which
> is reported in http://lkml.org/lkml/2009/12/1/371.
> 
> This patch also fixes http://bugzilla.kernel.org/show_bug.cgi?id=14483
> 
> Reported-and-bisected-by: Larry Finger <Larry.Finger@...inger.net>
> Reported-and-bisected-by: Justin P. Mattock <justinmattock@...il.com>
> Signed-off-by: Xiaotian Feng <dfeng@...hat.com>
> Cc: Len Brown <lenb@...nel.org>
> Cc: Bob Moore <robert.moore@...el.com>
> Cc: Lin Ming <ming.m.lin@...el.com>
> Cc: Alexey Starikovskiy <astarikovskiy@...e.de>
> Cc: Pavel Machek <pavel@....cz>
> ---
>  include/acpi/platform/aclinux.h |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/include/acpi/platform/aclinux.h b/include/acpi/platform/aclinux.h
> index 9d7febd..0946997 100644
> --- a/include/acpi/platform/aclinux.h
> +++ b/include/acpi/platform/aclinux.h
> @@ -152,7 +152,7 @@ static inline void *acpi_os_acquire_object(acpi_cache_t * cache)
>  #include <linux/hardirq.h>
>  #define ACPI_PREEMPTION_POINT() \
>  	do { \
> -		if (!in_atomic_preempt_off()) \
> +		if (!in_atomic_preempt_off() && !irqs_disabled()) \
>  			cond_resched(); \
>  	} while (0)
>  

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