linux-kernel - Re: WARNING: at kernel/lockdep.c:690 __lock

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Message-ID: <alpine.DEB.2.00.1110151529570.25063@chino.kir.corp.google.com>
Date:	Sat, 15 Oct 2011 15:32:32 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Borislav Petkov <bp@...en8.de>,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Tejun Heo <tj@...nel.org>, Tejun Heo <htejun@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: WARNING: at kernel/lockdep.c:690 __lock_acquire+0x168/0x164b()

On Sun, 16 Oct 2011, Borislav Petkov wrote:

> > I think this is a problem with lockdep itself, could you try reverting 
> > f59de8992aa6 ("lockdep: Clear whole lockdep_map on initialization") if 
> > this reliably happens everytime you reboot (lockdep will only emit this 
> > once and then will suppress future warnings until the next boot)?
> > 
> > I think the new memset() is inadvertently clearing the name for 
> > double_unlock_balance().
> 
> Great,
> 
> so I'm not the only one seeing the above:
> http://marc.info/?l=linux-kernel&m=131468805610527
> 
> Due to it being very hard to reproduce, we dismissed it then as a
> possible hw corruption.
> 
> But yeah, it looks like I have triggered it on -rc9 too, just the
> other day. Oh, and I see -rc6 and -rc8 warnings in the logs too. Ok,
> correction, not that hard to trigger.
> 

Could you try to revert f59de8992aa6 ("lockdep: Clear whole lockdep_map on 
initialization") with this patch and see if it helps?  Thanks.
---
diff --git a/kernel/lockdep.c b/kernel/lockdep.c
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -2874,7 +2874,10 @@ static int mark_lock(struct task_struct *curr, struct held_lock *this,
 void lockdep_init_map(struct lockdep_map *lock, const char *name,
 		      struct lock_class_key *key, int subclass)
 {
-	memset(lock, 0, sizeof(*lock));
+	int i;
+
+	for (i = 0; i < NR_LOCKDEP_CACHING_CLASSES; i++)
+		lock->class_cache[i] = NULL;
 
 #ifdef CONFIG_LOCK_STAT
 	lock->cpu = raw_smp_processor_id();
--
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