From a68e5c94f7d3dd64fef34dd5d97e365cae4bb42a Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Fri, 17 Sep 2010 17:06:46 -0700 Subject: [PATCH] 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 Signed-off-by: H. Peter Anvin Cc: Arjan van de Ven Cc: Len Brown Cc: Venkatesh Pallipadi Cc: Peter Zijlstra LKML-Reference: --- arch/x86/kernel/smpboot.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 07bf4233441d..55c80ffb8719 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -1422,9 +1422,9 @@ static inline void mwait_play_dead(void) (highest_subcstate - 1); } + wbinvd(); + while (1) { - mb(); - wbinvd(); __monitor(¤t_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(); } }