linux-kernel - Re: linux-next oops in __lock_acquire for process_one

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Message-ID: <20120508165819.GB10687@google.com>
Date:	Tue, 8 May 2012 09:58:19 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Hugh Dickins <hughd@...gle.com>, Ingo Molnar <mingo@...hat.com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Yong Zhang <yong.zhang0@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: linux-next oops in __lock_acquire for process_one_work

On Tue, May 08, 2012 at 03:03:22PM +0200, Peter Zijlstra wrote:
> I think there's a problem if indeed we do silly things like small copies
> like Hugh saw (why would gcc ever generate small copies for objects that
> are naturally aligned and naturally sized?).
> 
> Something like the below should fix that problem, but it doesn't explain
> the observed issue..

Hmmm.... Hugh, can you please verify whether this patch makes the
problem go away somehow?

> @@ -1810,7 +1810,7 @@ __acquires(&gcwq->lock)
>  	 * lock freed" warnings as well as problems when looking into
>  	 * work->lockdep_map, make a copy and use that here.
>  	 */
> -	struct lockdep_map lockdep_map = work->lockdep_map;
> +	struct lockdep_map lockdep_map = lockdep_copy_map(&work->lockdep_map);

If this is the correct fix for whatever reason, maybe we want the copy
interface to be a bit more conventional?  lockdep_copy_map(to, from)?

Thanks.

-- 
tejun
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