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x86, hotplug: Move WBINVD back outside the play_dead loop

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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>
This commit is contained in:
H. Peter Anvin 2010-09-17 17:06:46 -07:00
parent ea53069231
commit a68e5c94f7
1 changed files with 5 additions and 6 deletions
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11
arch/x86/kernel/smpboot.c
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@ -1422,9 +1422,9 @@ static inline void mwait_play_dead(void)
(highest_subcstate - 1);
}
wbinvd();
while (1) {
mb();
wbinvd();
__monitor(&current_thread_info()->flags, 0, 0);
mb();
__mwait(eax, 0);
@ -1433,11 +1433,10 @@ static inline void mwait_play_dead(void)
static inline void hlt_play_dead(void)
{
if (current_cpu_data.x86 >= 4)
wbinvd();
while (1) {
mb();
if (current_cpu_data.x86 >= 4)
wbinvd();
mb();
native_halt();
}
}