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From: Ingo Molnar <mingo@elte.hu>
To: tglx@linutronix.de
Cc: akpm@osdl.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2.6.10-mm2] Fix preemption race [1/3] (Core)
Date: Mon, 10 Jan 2005 10:15:59 +0100	[thread overview]
Message-ID: <20050110091559.GB25034@elte.hu> (raw)
In-Reply-To: <20050110013508.1.patchmail@tglx>


* tglx@linutronix.de <tglx@linutronix.de> wrote:

> The idle-thread-preemption-fix.patch introduced a race, which is not
> critical, but might give us an extra turn through the scheduler. When
> interrupts are reenabled in entry.c and an interrupt occures before we
> reach the add_preempt_schedule() in preempt_schedule we get
> rescheduled again in the return from interrupt path.

i agree that there's a race. I solved this in the -RT patchset a couple
of weeks ago, but in a different wasy. I introduced the
preempt_schedule_irq() function and this solves the problem via keeping
the whole IRQ-preemption path irqs-off. This has the advantage that if
an IRQ signals preemption of a task and the kernel is immediately
preemptable then we are able to hit that task atomically without
re-enabling IRQs again. I'll split out this patch - can you see any
problems with the preempt_schedule_irq() approach?

	Ingo

  parent reply	other threads:[~2005-01-10  9:16 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2005-01-10  0:35 [PATCH 2.6.10-mm2] Fix preemption race [1/3] (Core) tglx
2005-01-10  0:53 ` [PATCH 2.6.10-mm2] Use the new preemption code [2/3] Thomas Gleixner
2005-01-10  1:06   ` Russell King
2005-01-10  1:18     ` [PATCH 2.6.10-mm2] Use the new preemption code [2/3] Resend Thomas Gleixner
2005-01-10  7:32       ` Andrew Morton
2005-01-10 10:57         ` Thomas Gleixner
2005-01-10  9:46       ` Russell King
2005-01-10 10:12         ` Thomas Gleixner
2005-01-10 11:02           ` Ingo Molnar
2005-01-10 13:46             ` Thomas Gleixner
2005-01-10  1:00 ` [PATCH 2.6.10-mm2] Use the new preemption code [3/3] Thomas Gleixner
2005-01-10 14:56   ` Tom Rini
2005-01-10 15:49     ` tglx
2005-01-10  9:15 ` Ingo Molnar [this message]
2005-01-10 10:14   ` [PATCH 2.6.10-mm2] Fix preemption race [1/3] (Core) Thomas Gleixner
  -- strict thread matches above, loose matches on Subject: below --
2005-01-10  0:34 tglx

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