Subject: [linux-audio-dev] Re: lowish-latency patch for 2.4.0-test9
From: Andi Kleen (ak_AT_suse.de)
Date: Fri Oct 06 2000 - 16:39:20 EEST
On Fri, Oct 06, 2000 at 10:00:36PM +1100, Andrew Morton wrote:
> The little-low-latency patch for test9 is at
>
> http://www.uow.edu.au/~andrewm/linux/2.4.0-test9-low-latency.patch
>
> Notes:
>
> - It now passes Benno's tests with 50% headroom (thanks to
> Ingo's scheduler race fix).
What was that race exactly ?
There is a scheduler race which may also hurt (and is harder to fix):
when the timer interrupt hits in syscall exit after the need_resched check
was done then you may lose a time slice. The window can be quite long
when signals are handled (after do_signal returned there is no reschedule
check). Without signals it is only a few instructions window.
I have not checked if it really is a problem in practice though. With
lots of signals it may be a problem.
-Andi
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