commit f1e3a093 upstream.

Probability of use-after-free isn't zero in this place.
Signed-off-by: Kirill Tkhai <ktkhai@parallels.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20140922183636.11015.83611.stgit@localhostSigned-off-by: Ingo Molnar <mingo@kernel.org>
[ luis: backported to 3.16: used peterz's backport to 3.17 ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>