From: Ingo Molnar <mingo@elte.hu>
To: linux-ia64@vger.kernel.org
Subject: [Linux-ia64] Re: O(1) scheduler "complex" macros
Date: Wed, 10 Jul 2002 18:31:03 +0000 [thread overview]
Message-ID: <marc-linux-ia64-105590701905747@msgid-missing> (raw)
In-Reply-To: <marc-linux-ia64-105590701905752@msgid-missing>
On Tue, 9 Jul 2002, Erich Focht wrote:
> Suppose we have
> cpu1: idle1
> cpu2: prev2 -> next2 (in the switch)
>
> I don't understand how task_lock(prev2) done on cpu2 can prevent cpu1 to
> schedule prev2, which it stole after the RQ#2 lock release. It will just
> try to task_lock(idle1), which will be successfull.
you are right - the 'complex' macros also need to lock the 'next' task,
not only the 'previous' task - but to do that deadlock-free, they need to
drop the runqueue lock ...
Ingo
next prev parent reply other threads:[~2002-07-10 18:31 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-07-10 9:05 [Linux-ia64] Re: O(1) scheduler "complex" macros Erich Focht
2002-07-10 12:34 ` Erich Focht
2002-07-10 18:31 ` Ingo Molnar [this message]
2002-07-10 19:30 ` Ingo Molnar
2002-07-11 9:25 ` Erich Focht
2002-07-11 9:31 ` Ingo Molnar
2002-07-11 9:39 ` Ingo Molnar
2002-07-11 9:52 ` Ingo Molnar
2002-07-12 12:39 ` Pavel Machek
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