netdev - Re: [PATCH] net: fec: use reinit_completion() in mdio accessor functions

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Message-Id: <20150825.163332.1359468744424655533.davem@davemloft.net>
Date:	Tue, 25 Aug 2015 16:33:32 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	rmk+kernel@....linux.org.uk
Cc:	B38611@...escale.com, netdev@...r.kernel.org
Subject: Re: [PATCH] net: fec: use reinit_completion() in mdio accessor
 functions

From: Russell King <rmk+kernel@....linux.org.uk>
Date: Tue, 25 Aug 2015 09:49:53 +0100

> Rather than re-initialising the entire completion on every mdio access,
> use reinit_completion() which only resets the completion count.  This
> avoids possible reinitialisation of the contained spinlock and waitqueue
> while they may be in use (eg, mid-completion.)
> 
> Such an event could occur if there's a long delay in interrupt handling
> causing the mdio accessor to time out, then a second access comes in
> while the interrupt handler on a different CPU has called complete().
> Another scenario where this has been observed is while locking has
> been missing at the phy layer, allowing concurrent attempts to access
> the MDIO bus.
> 
> Signed-off-by: Russell King <rmk+kernel@....linux.org.uk>

Applied.
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