Re: [PATCH 51/51] net/iucv/iucv.c: Fix CPU hotplug callbackregistration

From: David Miller
Date: Thu Feb 06 2014 - 23:39:46 EST

From: "Srivatsa S. Bhat" <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>
Date: Thu, 06 Feb 2014 03:43:55 +0530

> Subsystems that want to register CPU hotplug callbacks, as well as perform
> initialization for the CPUs that are already online, often do it as shown
> below:
> This is wrong, since it is prone to ABBA deadlocks involving the
> cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
> with CPU hotplug operations).
> Instead, the correct and race-free way of performing the callback
> registration is:
> Fix the code in net/iucv/iucv.c by using this latter form of callback
> registration. Also, provide helper functions to perform the common memory
> allocations and frees, to condense repetitive code.
> Cc: Ursula Braun <ursula.braun@xxxxxxxxxx>
> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> Cc: linux-s390@xxxxxxxxxxxxxxx
> Cc: netdev@xxxxxxxxxxxxxxx
> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>

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