linux-kernel - Re: [PATCH] ACPICA: don't cond_resched() when irq_disabled or in

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Date:	Thu, 10 Dec 2009 21:37:59 +0300
From:	Alexey Starikovskiy <aystarik@...il.com>
To:	Pavel Machek <pavel@....cz>
CC:	Xiaotian Feng <dfeng@...hat.com>, lenb@...nel.org,
	ming.m.lin@...el.com, robert.moore@...el.com,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ACPICA: don't cond_resched() when irq_disabled or in_atomic

Pavel Machek пишет:
> On Thu 2009-12-10 20:58:45, Alexey Starikovskiy wrote:
>   
>> Hi Pavel,
>>
>> Please elaborate... Your comments "ugly as hell" are too often to be
>> specific...
>> There is only one use of ACPI_PREEMPTION_POINT(), and it is in the
>> ACPICA code,
>> which we all agreed to keep OS independent, thus the need for #define.
>> Do you see any other way to add preemption point without introducing
>> Linux-specific
>> code into ACPICA?
>>     
>
> I believe we want linux-specific code in acpica at this point.
>
>   
The point there we call cond_resched() in ACPICA is an interpreter parse
loop. This parse loop may be executed from within atomic context and even
with interrupts off. In this case, cond_resched() should not be called
to not make
might_sleep() guards angry.

Please post the code, which will do the above and will not look "ugly as
hell".
I still don't follow your vague comments.
> (Or maybe... I guess other systems have concept of preemption and not
> all actions are permitted from all contexts, so maybe something like
> that would be important for them, too?)
>   
None of them cared about it up to this point.
With the macro above we allowed them to follow Linux, but to go or not
is their call.

Regards,
Alex.
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