Messages in this thread Patch in this message | | | Date | Sat, 18 Sep 2010 00:13:05 GMT | From | "tip-bot for H. Peter Anvin" <> | Subject | [tip:x86/idle] x86, hotplug: Move WBINVD back outside the play_dead loop |
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Commit-ID: a68e5c94f7d3dd64fef34dd5d97e365cae4bb42a Gitweb: http://git.kernel.org/tip/a68e5c94f7d3dd64fef34dd5d97e365cae4bb42a Author: H. Peter Anvin <hpa@linux.intel.com> AuthorDate: Fri, 17 Sep 2010 17:06:46 -0700 Committer: H. Peter Anvin <hpa@linux.intel.com> CommitDate: Fri, 17 Sep 2010 17:10:23 -0700
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> --- arch/x86/kernel/smpboot.c | 11 +++++------ 1 files changed, 5 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 07bf423..55c80ffb 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(); } }
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