tick: Cleanup NOHZ per cpu data on cpu down, TNX VOKU!

Commit-ID:  ae7868e241c015aadc8632d9fe633a102a5918f6
Gitweb:     http://git.kernel.org/tip/ae7868e241c015aadc8632d9fe633a102a5918f6
Author:     Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Fri, 3 May 2013 15:02:50 +0200
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Sun, 5 May 2013 08:15:11 +0200

tick: Cleanup NOHZ per cpu data on cpu down

Prarit reported a crash on CPU offline/online. The reason is that on
CPU down the NOHZ related per cpu data of the dead cpu is not cleaned
up. If at cpu online an interrupt happens before the per cpu tick
device is registered the irq_enter() check potentially sees stale data
and dereferences a NULL pointer.

Cleanup the data after the cpu is dead.

Reported-by: Prarit Bhargava <prarit@redhat.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1305031451561.2886@ionos
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Kernel 9.24 JB CM/AOKP ONLY!