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

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Date:	Wed, 17 Sep 2014 11:28:27 +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 Tue, 2014-09-16 at 09:48 +0200, Richard Weinberger wrote:
> If sync_erase() failes with EINTR, ENOMEM, EAGAIN or
> EBUSY erase_worker() re-schedules the failed work.
> This will lead to a deadlock because erase_worker() is called
> with work_sem held in read mode. And schedule_erase() will take
> this lock again.

IIRC, the assumption was that the R/W semaphore may be taken in read
mode many times, so it wouldn't hurt to do:

down_read()
down_read()
up_read()
up_read()

If this is right, then the lockdep warning is incorrect.

-- 
Best Regards,
Artem Bityutskiy

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