From: Ingo Molnar <mingo@elte.hu>
To: Linus Torvalds <torvalds@osdl.org>
Cc: Fernando Lopez-Lezcano <nando@ccrma.Stanford.EDU>,
Andrew Morton <akpm@osdl.org>,
linux-kernel@vger.kernel.org, Andi Kleen <ak@suse.de>,
Len Brown <len.brown@intel.com>
Subject: Re: [patch] sched: fix bad missed wakeups in the i386, x86_64, ia64, ACPI and APM idle code
Date: Thu, 21 Dec 2006 14:00:12 +0100 [thread overview]
Message-ID: <20061221130012.GA21854@elte.hu> (raw)
In-Reply-To: <20061221121656.GA9263@elte.hu>
* Ingo Molnar <mingo@elte.hu> wrote:
> CPU idle wakeup very much depends on ordered memory ops, the clearing
> of the TS_POLLING flag must always be done before we test
> need_resched() and hit the idle instruction(s). [Symmetrically, the
> wakeup code needs to set NEED_RESCHED before it tests the TS_POLLING
> flag, so memory ordering is paramount.]
Btw., this means that an smp_rmb() ought to be enough too. (I sent such
a test-patch to Fernando.) Also, i'd like the change to smp_rmb() be
done separately from the fix so that we have the most-conservative
variant in and thus it becomes bisectable. I'd like to avoid another few
months of latency for fixing yet another bug in this area...
Ingo
prev parent reply other threads:[~2006-12-21 13:02 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-12-21 12:16 Ingo Molnar
2006-12-21 13:00 ` Ingo Molnar [this message]
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