From: Artem Bityutskiy <dedekind1@gmail.com>
To: Richard Weinberger <richard@nod.at>
Cc: linux-mtd@lists.infradead.org, computersforpeace@gmail.com,
dwmw2@infradead.org, linux-kernel@vger.kernel.org,
stable@vger.kernel.org
Subject: Re: [PATCH] UBI: Fix possible deadlock in erase_worker()
Date: Wed, 17 Sep 2014 11:28:27 +0300 [thread overview]
Message-ID: <1410942507.28850.78.camel@sauron.fi.intel.com> (raw)
In-Reply-To: <1410853702-11616-1-git-send-email-richard@nod.at>
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
WARNING: multiple messages have this Message-ID (diff)
From: Artem Bityutskiy <dedekind1@gmail.com>
To: Richard Weinberger <richard@nod.at>
Cc: dwmw2@infradead.org, computersforpeace@gmail.com,
linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org,
stable@vger.kernel.org
Subject: Re: [PATCH] UBI: Fix possible deadlock in erase_worker()
Date: Wed, 17 Sep 2014 11:28:27 +0300 [thread overview]
Message-ID: <1410942507.28850.78.camel@sauron.fi.intel.com> (raw)
In-Reply-To: <1410853702-11616-1-git-send-email-richard@nod.at>
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
next prev parent reply other threads:[~2014-09-17 8:28 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-16 7:48 [PATCH] UBI: Fix possible deadlock in erase_worker() Richard Weinberger
2014-09-16 7:48 ` Richard Weinberger
2014-09-17 8:28 ` Artem Bityutskiy [this message]
2014-09-17 8:28 ` Artem Bityutskiy
2014-09-17 8:40 ` Richard Weinberger
2014-09-17 8:40 ` Richard Weinberger
2014-09-17 8:43 ` Artem Bityutskiy
2014-09-17 8:43 ` Artem Bityutskiy
2014-09-17 9:35 ` Artem Bityutskiy
2014-09-17 9:35 ` Artem Bityutskiy
2014-09-19 9:46 ` Richard Weinberger
2014-09-19 9:46 ` Richard Weinberger
2014-09-19 10:47 ` Artem Bityutskiy
2014-09-19 10:47 ` Artem Bityutskiy
2014-09-19 11:01 ` Richard Weinberger
2014-09-19 11:01 ` Richard Weinberger
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