linux-kernel - [PATCH 17/20] x86/ticketlock: clarify barrier in arch_spin

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Message-Id: <ba397357a160b73c800a608a52256544904c6324.1288794124.git.jeremy.fitzhardinge@citrix.com>
Date:	Wed,  3 Nov 2010 10:59:58 -0400
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Nick Piggin <npiggin@...e.de>,
	Jan Beulich <JBeulich@...ell.com>, Avi Kivity <avi@...hat.com>,
	Xen-devel <xen-devel@...ts.xensource.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linux Virtualization <virtualization@...ts.linux-foundation.org>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
Subject: [PATCH 17/20] x86/ticketlock: clarify barrier in arch_spin_lock

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

Make sure the barrier in arch_spin_lock is definitely in the code path.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
---
 arch/x86/include/asm/spinlock.h |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h
index 158b330..c7455e1 100644
--- a/arch/x86/include/asm/spinlock.h
+++ b/arch/x86/include/asm/spinlock.h
@@ -151,13 +151,13 @@ static __always_inline void arch_spin_lock(struct arch_spinlock *lock)
 
 		do {
 			if (inc.head == inc.tail)
-				return;
+				goto out;
 			cpu_relax();
 			inc.head = ACCESS_ONCE(lock->tickets.head);
 		} while (--count);
 		__ticket_lock_spinning(lock, inc.tail);
 	}
-	barrier();		/* make sure nothing creeps before the lock is taken */
+out:	barrier();		/* make sure nothing creeps before the lock is taken */
 }
 
 static __always_inline int arch_spin_trylock(arch_spinlock_t *lock)
-- 
1.7.2.3

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