From: H. Peter Anvin <hpa@linux.intel.com>
Date: Thu, 19 Dec 2013 20:30:03 +0000 (-0800)
Subject: x86, idle: Add memory barriers around clflush in mwait_play_dead()
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=7d590cca7cd2cce4ed7c47d221d6f90566653ba8;p=GitHub%2Fexynos8895%2Fandroid_kernel_samsung_universal8895.git

x86, idle: Add memory barriers around clflush in mwait_play_dead()

For consistency with mwait_idle_with_hints().  Not sure they help, but
they really won't hurt...

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Len Brown <len.brown@intel.com>
Link: http://lkml.kernel.org/r/CA%2B55aFzGxcML7j8CEvQPYzh0W81uVoAAVmGctMOUZ7CZ1yYd2A@mail.gmail.com
---

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 85dc05a3aa02..f5252c4eec8c 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1417,7 +1417,9 @@ static inline void mwait_play_dead(void)
 		 * The WBINVD is insufficient due to the spurious-wakeup
 		 * case where we return around the loop.
 		 */
+		mb();
 		clflush(mwait_ptr);
+		mb();
 		__monitor(mwait_ptr, 0, 0);
 		mb();
 		__mwait(eax, 0);