From: Tejun Heo <tj@kernel.org>
To: David Rientjes <rientjes@google.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Ingo Molnar <mingo@elte.hu>, Borislav Petkov <bp@alien8.de>,
Peter Zijlstra <peterz@infradead.org>,
linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: WARNING: at kernel/lockdep.c:690 __lock_acquire+0x168/0x164b()
Date: Thu, 20 Oct 2011 14:36:44 -0700 [thread overview]
Message-ID: <20111020213644.GB25124@google.com> (raw)
In-Reply-To: <alpine.DEB.2.00.1110201425560.5552@chino.kir.corp.google.com>
Hello,
On Thu, Oct 20, 2011 at 02:31:39PM -0700, David Rientjes wrote:
> > So, according to this thread, the problem is that the memset() clears
> > lock->name field, right?
>
> Right, and reverting f59de8992aa6 ("lockdep: Clear whole lockdep_map on
> initialization") seems to fix the lockdep warning.
>
> > But how can that be a problem? lock->name
> > is always set to either "NULL" or @name. Why would clearing it before
> > setting make any difference? What am I missing?
> >
>
> The scheduler (in sched_fair and sched_rt) calls lock_set_subclass() which
> sets the name in double_unlock_balance() to set the name but there's a
> race between when that is cleared with the memset() and setting of
> lock->name where lockdep can find them to match.
Hmmm... so lock_set_subclass() is racing against lockdep_init()? That
sounds very fishy and probably needs better fix. Anyways, if someone
can't come up with proper solution, please feel free to revert the
commit.
Thanks.
--
tejun
next prev parent reply other threads:[~2011-10-20 21:36 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-15 20:12 WARNING: at kernel/lockdep.c:690 __lock_acquire+0x168/0x164b() Sergey Senozhatsky
2011-10-15 21:42 ` David Rientjes
2011-10-15 22:23 ` Borislav Petkov
2011-10-15 22:32 ` David Rientjes
2011-10-16 5:09 ` Sergey Senozhatsky
2011-10-20 18:39 ` Borislav Petkov
2011-10-20 18:53 ` Sergey Senozhatsky
2011-10-20 19:07 ` Sergey Senozhatsky
2011-10-20 21:17 ` David Rientjes
2011-10-20 21:23 ` Tejun Heo
2011-10-20 21:31 ` David Rientjes
2011-10-20 21:36 ` Tejun Heo [this message]
2011-10-20 23:00 ` Sergey Senozhatsky
2011-10-21 9:14 ` David Rientjes
2011-10-21 9:26 ` Sergey Senozhatsky
2011-10-21 9:45 ` Yong Zhang
2011-11-03 7:17 ` Sergey Senozhatsky
2011-11-03 7:27 ` Yong Zhang
2011-11-03 7:45 ` Sergey Senozhatsky
2011-11-03 7:53 ` Yong Zhang
2011-11-04 9:25 ` Borislav Petkov
2011-11-04 9:31 ` Sergey Senozhatsky
2011-11-07 4:54 ` Yong Zhang
2011-11-07 8:43 ` Sergey Senozhatsky
2011-11-04 9:34 ` Yong Zhang
2011-11-04 9:51 ` Sergey Senozhatsky
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