From: ebiederm@xmission.com (Eric W. Biederman)
To: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>,
Tavis Ormandy <taviso@google.com>, Jeff Dike <jdike@addtoit.com>,
Julien Tinnes <jln@google.com>, Matt Mackall <mpm@selenic.com>,
Americo Wang <xiyou.wangcong@gmail.com>,
LKML <linux-kernel@vger.kernel.org>,
Oleg Nesterov <oleg@redhat.com>,
Alan Cox <alan@lxorguk.ukuu.org.uk>
Subject: Re: [2.6.33-rc5] starting emacs makes lockdep warning
Date: Mon, 25 Jan 2010 22:17:15 -0800 [thread overview]
Message-ID: <m14om9jspg.fsf@fess.ebiederm.org> (raw)
In-Reply-To: <20100126144641.5AB3.A69D9226@jp.fujitsu.com> (KOSAKI Motohiro's message of "Tue\, 26 Jan 2010 14\:49\:12 +0900 \(JST\)")
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> writes:
>> > On Tue, Jan 26, 2010 at 11:20 AM, KOSAKI Motohiro
>> > <kosaki.motohiro@jp.fujitsu.com> wrote:
>> > > Hi
>> > >
>> > > Current linus tree made following lockdep warning when starting emacs command.
>> > > Is this known issue?
>> > >
>> > >
>> > > =========================================================
>> > > [ INFO: possible irq lock inversion dependency detected ]
>> > > 2.6.33-rc5 #77
>> > > ---------------------------------------------------------
>> > > emacs/1609 just changed the state of lock:
>> > > (&(&tty->ctrl_lock)->rlock){+.....}, at: [<ffffffff8127c648>] tty_fasync+0xe8/0x190
>> > > but this lock took another, HARDIRQ-unsafe lock in the past:
>> > > (&(&sighand->siglock)->rlock){-.....}
>> > >
>> > > and interrupts could create inverse lock ordering between them.
>> > >
>> > >
>> >
>> > Hey,
>> >
>> > does reverting commit 703625118 help?
>>
>> Seems solved.
>>
>> Thanks.
>
> I'm sorry.
> I forgot to cc related person at last mail.
>
> Greg, can you please consider revert commit 703625118?
It looks like f_modown needs to do irqsave irqrestore to be safely
called in this context. My apologies for missing this when I
originally made the suggestion.
As for the other comments I would be very surprised if lock_kernel()
offers any real protection.
I really don't understand what it is talking about siglock being
irq unsafe, that seems wrong on oh so many levels.
Eric
n
next prev parent reply other threads:[~2010-01-26 6:17 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-01-26 3:20 [2.6.33-rc5] starting emacs makes lockdep warning KOSAKI Motohiro
2010-01-26 5:25 ` Américo Wang
2010-01-26 5:37 ` KOSAKI Motohiro
2010-01-26 5:49 ` KOSAKI Motohiro
2010-01-26 6:01 ` Américo Wang
2010-01-26 6:07 ` Al Viro
2010-01-26 6:24 ` Américo Wang
2010-01-26 6:54 ` Al Viro
2010-01-26 7:45 ` KOSAKI Motohiro
2010-01-26 8:45 ` Américo Wang
2010-01-26 9:14 ` Eric W. Biederman
2010-01-26 9:32 ` Américo Wang
2010-01-26 12:33 ` Eric W. Biederman
2010-01-26 15:58 ` [Patch] fix the lockdep warning in tty_fasync() Américo Wang
2010-01-27 1:09 ` KOSAKI Motohiro
2010-01-27 1:47 ` Greg KH
2010-01-26 6:17 ` Eric W. Biederman [this message]
2010-01-26 18:16 ` check_usage_backwards() && forwards? (Was: [2.6.33-rc5] starting emacs makes lockdep warning) Oleg Nesterov
2010-01-26 18:47 ` Peter Zijlstra
2010-01-27 2:58 ` Américo Wang
2010-01-27 13:15 ` [tip:core/urgent] lockdep: Fix check_usage_backwards() error message tip-bot for Oleg Nesterov
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