From: Arnd Bergmann <arnd@arndb.de>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
Rusty Russell <rusty@rustcorp.com.au>,
Kay Sievers <kay.sievers@vrfy.org>,
Brandon Philips <brandon@ifup.org>
Subject: Re: [BUG 2.6.36-rc6] list corruption in module_bug_finalize
Date: Mon, 4 Oct 2010 13:00:14 +0200 [thread overview]
Message-ID: <201010041300.15234.arnd@arndb.de> (raw)
In-Reply-To: <alpine.LFD.2.00.1010032141410.14550@localhost6.localdomain6>
On Sunday 03 October 2010, Thomas Gleixner wrote:
> Current mainline triggers a list corruption bug in
> module_bug_finalize(). dmesg excerpt below.
>
> The corresponding code says:
>
> /*
> * Strictly speaking this should have a spinlock to protect against
> * traversals, but since we only traverse on BUG()s, a spinlock
> * could potentially lead to deadlock and thus be counter-productive.
> */
> list_add(&mod->bug_list, &module_bug_list);
>
> I can see the traversal problem vs. BUG(), but what's protecting the
> list_add() ? BKL probably did, but is that true anymore ?
BKL hasn't been in this code path since before git.
I think this relatively recent change caused module_finalize to be
called without module_mutex held:
commit 75676500f8298f0ee89db12db97294883c4b768e
Author: Rusty Russell <rusty@rustcorp.com.au>
Date: Sat Jun 5 11:17:36 2010 -0600
module: make locking more fine-grained.
Kay Sievers <kay.sievers@vrfy.org> reports that we still have some
contention over module loading which is slowing boot.
Linus also disliked a previous "drop lock and regrab" patch to fix the
bne2 "gave up waiting for init of module libcrc32c" message.
This is more ambitious: we only grab the lock where we need it.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Brandon Philips <brandon@ifup.org>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Arnd
next prev parent reply other threads:[~2010-10-04 11:00 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-03 19:51 [BUG 2.6.36-rc6] list corruption in module_bug_finalize Thomas Gleixner
2010-10-04 11:00 ` Arnd Bergmann [this message]
2010-10-04 22:43 ` Thomas Gleixner
2010-10-04 23:55 ` Linus Torvalds
2010-10-05 1:11 ` Linus Torvalds
2010-10-05 5:14 ` Rusty Russell
2010-10-05 7:30 ` Thomas Gleixner
2010-10-05 15:34 ` Linus Torvalds
2010-10-05 16:40 ` Thomas Gleixner
2010-10-05 17:17 ` Linus Torvalds
2010-10-05 17:43 ` Thomas Gleixner
2010-10-06 9:10 ` Rusty Russell
2010-10-05 4:18 ` Rusty Russell
2010-10-05 11:08 ` Adrian Bunk
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