From: cjb@laptop•org (Chris Ball)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH V2] mxs/spi: Fix misuse of init_completion
Date: Thu, 23 Aug 2012 22:44:17 -0400 [thread overview]
Message-ID: <87393dt3em.fsf@octavius.laptop.org> (raw)
In-Reply-To: <1345775624-9696-1-git-send-email-marex@denx.de> (Marek Vasut's message of "Fri, 24 Aug 2012 04:33:44 +0200")
Hi Marek,
On Thu, Aug 23 2012, Marek Vasut wrote:
> The init_completion() call does reinit not only the variable carrying
> the flag that the completion finished, but also initialized the
> waitqueue associated with the completion. On the contrary, the
> INIT_WAITQUEUE() call only reinits the flag.
>
> In case there was anything still stuck in the waitqueue, subsequent call
> to init_completion() would be able to create possible race condition. This
> patch uses the proper function and moves init_completion() into .probe() call
> of the driver, to be issued only once.
>
> Note that such scenario is impossible, since two threads can never enter the
> mxs_spi_txrx_dma(), since whole this section is protected by mutex in SPI core.
> This by no means allows this issue to exit though.
>
> Signed-off-by: Marek Vasut <marex@denx•de>
Thanks for writing that up -- I appreciate seeing the explanation of the
problems this could have caused.
- Chris.
--
Chris Ball <cjb@laptop•org> <http://printf.net/>
One Laptop Per Child
next prev parent reply other threads:[~2012-08-24 2:44 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-24 2:33 [PATCH V2] mxs/spi: Fix misuse of init_completion Marek Vasut
2012-08-24 2:44 ` Chris Ball [this message]
2012-08-24 2:54 ` Marek Vasut
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