From: H. Peter Anvin <hpa@linux.intel.com>
Date: Sat, 18 Sep 2010 00:06:46 +0000 (-0700)
Subject: x86, hotplug: Move WBINVD back outside the play_dead loop
X-Git-Tag: v2.6.37-rc1~205^2~1
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a68e5c94f7d3dd64fef34dd5d97e365cae4bb42a;p=pandora-kernel.git

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 <asit.k.mallick@intel.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Cc: Arjan van de Ven <arjan@linux.kernel.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Venkatesh Pallipadi <venki@google.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.hl>
LKML-Reference: <tip-ea53069231f9317062910d6e772cca4ce93de8c8@git.kernel.org>
---

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