linux-kernel - [tip:x86/idle] x86, idle: Add memory barriers around clflush in mwait_play

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Date:	Thu, 19 Dec 2013 12:33:23 -0800
From:	"tip-bot for H. Peter Anvin" <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
	torvalds@...ux-foundation.org, peterz@...radead.org,
	tglx@...utronix.de, hpa@...ux.intel.com, len.brown@...el.com
Subject: [tip:x86/idle] x86, idle:
  Add memory barriers around clflush in mwait_play_dead()

Commit-ID:  7d590cca7cd2cce4ed7c47d221d6f90566653ba8
Gitweb:     http://git.kernel.org/tip/7d590cca7cd2cce4ed7c47d221d6f90566653ba8
Author:     H. Peter Anvin <hpa@...ux.intel.com>
AuthorDate: Thu, 19 Dec 2013 12:30:03 -0800
Committer:  H. Peter Anvin <hpa@...ux.intel.com>
CommitDate: Thu, 19 Dec 2013 12:30:03 -0800

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@...ux.intel.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Len Brown <len.brown@...el.com>
Link: http://lkml.kernel.org/r/CA%2B55aFzGxcML7j8CEvQPYzh0W81uVoAAVmGctMOUZ7CZ1yYd2A@mail.gmail.com
---
 arch/x86/kernel/smpboot.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 85dc05a..f5252c4 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);
--
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