linux-kernel - Re: [PATCH] RCU: don't turn off lockdep when find suspicious rcu_dereference

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Date:	Tue, 20 Apr 2010 08:31:56 -0400
From:	Eric Paris <eparis@...hat.com>
To:	Lai Jiangshan <laijs@...fujitsu.com>
Cc:	paulmck@...ux.vnet.ibm.com, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Miles Lane <miles.lane@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] RCU: don't turn off lockdep when find suspicious
 rcu_dereference_check() usage

On Tue, 2010-04-20 at 16:23 +0800, Lai Jiangshan wrote:

> [PATCH] RCU: don't turn off lockdep when find suspicious rcu_dereference_check() usage
> 
> When suspicious rcu_dereference_check() usage is detected, lockdep is still
> available actually, so we should not call debug_locks_off() in
> lockdep_rcu_dereference().
> 
> For get rid of too much "suspicious rcu_dereference_check() usage"
> output when the "if(!debug_locks_off())" statement is removed. This patch uses
> static variable '__warned's for very usage of "rcu_dereference*()".
> 
> One variable per usage, so, Now, we can get multiple complaint
> when we detect multiple different suspicious rcu_dereference_check() usage.
> 
> Requested-by: Eric Paris <eparis@...hat.com>
> Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>

Although mine was a linux-next kernel and it doesn't appear that I have
rcu_dereference_protected() at all, so I dropped that bit of the patch,
it worked great!  I got 4 more complaints to harass people with.  Feel
free to add my tested by if you care to.

Tested-by: Eric Paris <eparis@...hat.com>

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