From: Andrew Morton <akpm@linux-foundation.org>
To: Ingo Molnar <mingo@elte.hu>
Cc: linux-kernel@vger.kernel.org
Subject: Re: circular locking: /proc/sys/vm/drop_caches
Date: Fri, 23 Feb 2007 02:07:43 -0800 [thread overview]
Message-ID: <20070223020743.28ede2d4.akpm@linux-foundation.org> (raw)
In-Reply-To: <20070223063538.GA13679@elte.hu>
> On Fri, 23 Feb 2007 07:35:38 +0100 Ingo Molnar <mingo@elte.hu> wrote:
> i just got the lockdep warning below when doing:
>
> echo 3 > /proc/sys/vm/drop_caches
>
> is this a known quirk in the drop_caches code?
It is - we're taking inode_lock at just the wrong level there and I don't
know how to fix it. The basic problem is that we're doing a list_head
walk: if we drop the lock we have to start again.
Well, I do know how to fix it: rip the various inode lists and use a tagged
radix tree instead - make writeback's per-superblock inode walk work the
same as writeback's per-inode page walk. That will also alow us to drop
the lock and then resume the drop_caches thing at the point where we left
off.
But it's a large change and has some quite tricky issues which need to be
carried over from the existing code and I don't have time to do it.
The only (lame) thing I can say for now is that drop_caches is a
debug-only, root-only thing :(
next prev parent reply other threads:[~2007-02-23 10:08 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-02-23 6:35 circular locking: /proc/sys/vm/drop_caches Ingo Molnar
2007-02-23 9:40 ` Frederik Deweerdt
2007-02-23 10:07 ` Andrew Morton [this message]
2007-02-23 11:36 ` Ingo Molnar
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