linux-kernel - [PATCH 7/7] x86/ticketlock: prevent memory accesses from reordered out of lock region

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Message-Id: <1a2b7854c6cca125d867281969cadb97f79a6c93.1308259496.git.jeremy.fitzhardinge@citrix.com>
Date:	Thu, 16 Jun 2011 14:40:54 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	the arch/x86 maintainers <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Nick Piggin <npiggin@...nel.dk>,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
Subject: [PATCH 7/7] x86/ticketlock: prevent memory accesses from reordered out of lock region

From: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
---
 arch/x86/include/asm/spinlock.h |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h
index 3afb1a7..dac6fc6 100644
--- a/arch/x86/include/asm/spinlock.h
+++ b/arch/x86/include/asm/spinlock.h
@@ -114,6 +114,7 @@ static __always_inline int __ticket_spin_trylock(arch_spinlock_t *lock)
 
 static __always_inline void __ticket_spin_unlock(arch_spinlock_t *lock)
 {
+	barrier();		/* prevent reordering out of locked region */
 	__ticket_unlock_release(lock);
 	barrier();		/* prevent reordering into locked region */
 }
-- 
1.7.5.4

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