Date: Fri, 11 Feb 2005 18:30:25 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Daniel Walker <dwalker@mvista.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Interrupt starvation points
Message-ID: <20050211173025.GA17387@elte.hu>
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* Daniel Walker <dwalker@mvista.com> wrote:

>         I found some points during schedule when interrupts are off
> for long periods . These two patches seem to help. One enables
> interrupts inside schedule() , so that interrupts are enabled after
> each need-resched loop, then disabled again before __schedule() is
> called. 
> 
>         The other patch enabled interrupt before calling up on
> kernel_sem ..This one could use some thinking over. I did this cause
> up() is very expensive on ARM , and combined with the looping above
> interrupts can stay off for a long time .. 

i'm wondering what the best approach would be. Right now if
DIRECT_PREEMPT is enabled [it's disabled currently] and a higher-prio
task has been woken up we switch to it without ever enabling interrupts
again. Re-enabling interrupts during schedule() will reduce irq
latencies but will lengthen critical sections.

	Ingo
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