x86, hotplug: Move WBINVD back outside the play_dead loop
x86, hotplug: Move WBINVD back outside the play_dead loop

On processors with hyperthreading, when only one thread is offlined
the other thread can cause a spurious wakeup on the idled thread.  We
do not want to re-WBINVD when that happens.

Ideally, we should simply skip WBINVD unless we're the last thread on
a particular core to shut down, but there might be similar issues
elsewhere in the system.

Thus, revert to previous behavior of only WBINVD outside the loop.
Partly as a result, remove the mb()'s around it: they are not
necessary since wbinvd() is a serializing instruction, but they were
intended to make sure the compiler didn't do any funny loop
optimizations.

Reported-by: Asit Mallick <c85347359f7da9bbdabedc5329b600eadcf67627@intel.com>
Signed-off-by: H. Peter Anvin <8a453bad9912ffe59bc0f0b8abe03df9be19379e@linux.intel.com>
Cc: Arjan van de Ven <9043bf4b08f6c93a2cb55d98c3494b123858348f@linux.kernel.org>
Cc: Len Brown <b35faeaa9f67322de4a7df75e622f593a5cd06fe@kernel.org>
Cc: Venkatesh Pallipadi <0192021264f7ae88e4662be72db68a0c93b1d052@google.com>
Cc: Peter Zijlstra <645ca7d3a8d3d4f60557176cd361ea8351edc32b@chello.hl>
LKML-Reference: <656eea2b4135980bf16c6edad83a25c81500a78c@git.kernel.org>

KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs