linux-kernel - Re: [git pull] scheduler fixes

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Message-ID: <20090205001242.GC15680@elte.hu>
Date:	Thu, 5 Feb 2009 01:12:42 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Alexey Zaytsev <alexey.zaytsev@...il.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>
Subject: Re: [git pull] scheduler fixes


* Alexey Zaytsev <alexey.zaytsev@...il.com> wrote:

> On Mon, Feb 2, 2009 at 12:52, Peter Zijlstra <peterz@...radead.org> wrote:
> > On Sat, 2009-01-31 at 20:49 +0300, Alexey Zaytsev wrote:
> >> And answering an earlier question, this happens only on i386 and only
> >> with 4K stacks because x86_64 dosn't have a separate softirq stack,
> >> so the preempt count diring the soft irq is at least IRQ_EXIT_OFFSET.
> >
> > Which suggests that an initial preempt_count offset of 1 should suffice
> > to fix this issue and not confuse the softirq tracing, hmm?
> 
> Can't we just copy the preempt count when switching stacks?

that always has a dynamic cost and the thing is that after-switch we are 
fine with a constant count.

	Ingo
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