From: Pavel Machek <pavel@ucw.cz>
To: linux-ia64@vger.kernel.org
Subject: [Linux-ia64] Re: O(1) scheduler "complex" macros
Date: Fri, 12 Jul 2002 12:39:15 +0000 [thread overview]
Message-ID: <marc-linux-ia64-105590701905768@msgid-missing> (raw)
In-Reply-To: <marc-linux-ia64-105590701905752@msgid-missing>
Hi!
> > #define task_running(rq, p) \
> > ((rq)->curr = (p)) && !spin_is_locked(&(p)->switch_lock)
>
> one more implementational note: the above test is not 'sharp' in the sense
> that on SMP it's only correct (the test has no barriers) if the runqueue
> lock is held. This is true for all the critical task_running() uses in
> sched.c - and the cases that use it outside the runqueue lock are
> optimizations so they dont need an exact test.
I believe this is worth a *big fat* comment.
Pavel
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prev parent reply other threads:[~2002-07-12 12:39 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
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 [this message]
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