From: "Stephen C. Tweedie" <sct@redhat.com>
To: Rik van Riel <riel@nl.linux.org>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>,
Linux MM <linux-mm@kvack.org>, Stephen Tweedie <sct@redhat.com>,
Linux Kernel <linux-kernel@vger.rutgers.edu>
Subject: Re: 2.2.1{3,4,5pre*} VM bug found
Date: Thu, 27 Jan 2000 19:07:42 +0000 (GMT) [thread overview]
Message-ID: <14480.38782.751251.577294@dukat.scot.redhat.com> (raw)
In-Reply-To: <Pine.LNX.4.10.10001250421090.482-100000@mirkwood.dummy.home>
Hi,
On Tue, 25 Jan 2000 04:27:43 +0100 (CET), Rik van Riel
<riel@nl.linux.org> said:
> Sometimes a process with tsk->state != TASK_RUNNABLE
> calls __get_free_pages(). When we're (almost) out of
> memory, the process will wake up kswapd and try to
> free some memory itself.
> In 2.2.15pre4 or when the call to try_to_free_pages()
> generates disk I/O, the task will call schedule().
> Since the task state != TASK_RUNNABLE, schedule() will
> immedately remove it from the run queue ...
Shouldn't be a problem. Anywhere that we stall in try_to_free_pages()
to wait for disk IO, we obviously have to set task->state to
TASK_UNINTERRUPTIBLE, as we're about to block. If we do that as a
result of disk IO, then we have necessarily already scheduled a wakeup
event which will set the task state back to runnable.
So, the only risk is that the call to try_to_free_pages() has the
unexpected side effect of setting the task state to TASK_RUNNABLE. That
isn't a problem: the only effect it will have on the caller is to make a
call schedule() return sooner than expected.
--Stephen
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prev parent reply other threads:[~2000-01-27 19:07 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2000-01-25 3:27 2.2.1{3,4,5pre*} VM bug found Rik van Riel
2000-01-25 18:15 ` Andrea Arcangeli
2000-01-26 0:48 ` Rik van Riel
2000-01-27 19:09 ` Stephen C. Tweedie
2000-01-27 19:07 ` Stephen C. Tweedie [this message]
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