From 0316ae6d21c42caa65a8a5b148fd26cca3181a0f Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Mon, 20 Sep 2010 13:04:45 -0700 Subject: [PATCH] --- yaml --- r: 212050 b: refs/heads/master c: ce5f68246bf2385d6174856708d0b746dc378f20 h: refs/heads/master v: v3 --- [refs] | 2 +- trunk/arch/x86/kernel/smpboot.c | 20 +++++++++++++++++++- 2 files changed, 20 insertions(+), 2 deletions(-) diff --git a/[refs] b/[refs] index 871cda21c5c7..f01a70b9ef4d 100644 --- a/[refs] +++ b/[refs] @@ -1,2 +1,2 @@ --- -refs/heads/master: a68e5c94f7d3dd64fef34dd5d97e365cae4bb42a +refs/heads/master: ce5f68246bf2385d6174856708d0b746dc378f20 diff --git a/trunk/arch/x86/kernel/smpboot.c b/trunk/arch/x86/kernel/smpboot.c index 55c80ffb8719..fdccfe9dc63d 100644 --- a/trunk/arch/x86/kernel/smpboot.c +++ b/trunk/arch/x86/kernel/smpboot.c @@ -1394,9 +1394,12 @@ static inline void mwait_play_dead(void) unsigned int highest_cstate = 0; unsigned int highest_subcstate = 0; int i; + void *mwait_ptr; if (!cpu_has(¤t_cpu_data, X86_FEATURE_MWAIT)) return; + if (!cpu_has(¤t_cpu_data, X86_FEATURE_CLFLSH)) + return; if (current_cpu_data.cpuid_level < CPUID_MWAIT_LEAF) return; @@ -1422,10 +1425,25 @@ static inline void mwait_play_dead(void) (highest_subcstate - 1); } + /* + * This should be a memory location in a cache line which is + * unlikely to be touched by other processors. The actual + * content is immaterial as it is not actually modified in any way. + */ + mwait_ptr = ¤t_thread_info()->flags; + wbinvd(); while (1) { - __monitor(¤t_thread_info()->flags, 0, 0); + /* + * The CLFLUSH is a workaround for erratum AAI65 for + * the Xeon 7400 series. It's not clear it is actually + * needed, but it should be harmless in either case. + * The WBINVD is insufficient due to the spurious-wakeup + * case where we return around the loop. + */ + clflush(mwait_ptr); + __monitor(mwait_ptr, 0, 0); mb(); __mwait(eax, 0); }