From: Linus Torvalds <torvalds@linux-foundation.org>
To: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Ingo Molnar <mingo@elte.hu>, Roland McGrath <roland@redhat.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/3] wait_task_inactive: don't use the dummy version when !SMP && PREEMPT
Date: Wed, 30 Jul 2008 10:42:28 -0700 (PDT) [thread overview]
Message-ID: <alpine.LFD.1.10.0807301038170.3334@nehalem.linux-foundation.org> (raw)
In-Reply-To: <20080730170949.GA18682@tv-sign.ru>
On Wed, 30 Jul 2008, Oleg Nesterov wrote:
>
> The patch looks monstrous because it moves the (unchanged) definition
> of wait_task_inactive() outside of "#ifdef CONFIG_SMP", but it is quite
> trivial.
Hmm. Doesn't this just deadlock in UP (PREEMPT) if wait_task_interactive()
is ever called from a no-preempt context?
And if that's never the case, the comment should be updated to reflect
that (right now it says that it's only invalid to call it with interrupts
disabled to avoid cross-IPI deadlocks).
Oh, and shouldn't it do a "yield()" instead of a cpu_relax() on UP?
Inquiring minds want to know. That function was very much expressly
designed for SMP, not for preemption, and I want to understand why it's
ok (_if_ it's ok).
Linus
next prev parent reply other threads:[~2008-07-30 17:46 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-07-30 17:09 Oleg Nesterov
2008-07-30 17:42 ` Linus Torvalds [this message]
2008-07-30 18:13 ` Oleg Nesterov
2008-07-30 19:46 ` Dmitry Adamushko
2008-07-31 13:12 ` Oleg Nesterov
2008-07-31 2:22 ` Roland McGrath
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