linux-kernel - Re: [PATCH] UBI: Fix possible deadlock in erase

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Message-ID: <1410943421.28850.93.camel@sauron.fi.intel.com>
Date:	Wed, 17 Sep 2014 11:43:41 +0300
From:	Artem Bityutskiy <dedekind1@...il.com>
To:	Richard Weinberger <richard@....at>
Cc:	dwmw2@...radead.org, computersforpeace@...il.com,
	linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH] UBI: Fix possible deadlock in erase_worker()

On Wed, 2014-09-17 at 10:40 +0200, Richard Weinberger wrote:
> /*
>  * nested locking. NOTE: rwsems are not allowed to recurse
>  * (which occurs if the same task tries to acquire the same
>  * lock instance multiple times), but multiple locks of the
>  * same lock class might be taken, if the order of the locks
>  * is always the same. This ordering rule can be expressed
>  * to lockdep via the _nested() APIs, but enumerating the
>  * subclasses that are used. (If the nesting relationship is
>  * static then another method for expressing nested locking is
>  * the explicit definition of lock class keys and the use of
>  * lockdep_set_class() at lock initialization time.
>  * See Documentation/lockdep-design.txt for more details.)
>  */
> 
> In this case the same task is taking the same lock multiple times,
> which is not allowed according to rwsem.h.

Yes, this part was missed, thanks.

-- 
Best Regards,
Artem Bityutskiy

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