From: Trond Myklebust <trond.myklebust@fys.uio.no>
To: Joe Korty <joe.korty@ccur.com>, Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Al Viro <viro@zeniv.linux.org.uk>,
Steve French <sfrench@us.ibm.com>,
LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@elte.hu>
Subject: Re: circular locking dependency detected panic in filldir when CONFIG_PROVE_LOCKING=y
Date: Fri, 18 Sep 2009 17:39:01 -0400 [thread overview]
Message-ID: <1253309941.3183.104.camel@heimdal.trondhjem.org> (raw)
In-Reply-To: <20090918211550.GA8258@tsunami.ccur.com>
On Fri, 2009-09-18 at 17:15 -0400, Joe Korty wrote:
> I experienced a might_fault panic from NFS's use of filldir
> in a 2.6.31 kernel compiled with CONFIG_PROVE_LOCKING=y.
>
> Looking at filldir, I see it is accessing user space with
> __put_dir's (which are inatomic) and with one copy_to_user
> (which is not inatomic). It is the single copy_to_user
> which is causing the might_fault panic.
>
> It doesn't make any sense to be mixing use of inatomic
> and non-inatomic services in filldir. Either all should be
> the inatomic version, or none should be.
>
> The might_fault condition being reported by the panic looks
> real to me, so I suspect the wrong answer is converting
> everything to the inatomic version, since that just
> suppresses the circular dependency check while leaving
> the circular dependency in place.
Yes. This is known... Please see
http://thread.gmane.org/gmane.linux.nfs/28578
and
http://thread.gmane.org/gmane.linux.nfs/27406
I'm still hoping the VM folks can see fit to merge Peter's fix at some
point...
Cheers
Trond
next prev parent reply other threads:[~2009-09-18 21:39 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-09-18 21:15 Joe Korty
2009-09-18 21:39 ` Trond Myklebust [this message]
2009-09-19 7:23 ` Ingo Molnar
2009-09-19 11:19 ` Peter Zijlstra
2009-09-19 17:39 ` Ingo Molnar
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