linux-kernel - [PATCH RFC 03/12] x86/ticketlock: Use C for __ticket_spin

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Message-Id: <20100717004855.AE245A3C31@abulafia.goop.org>
Date:	Mon, 12 Jul 2010 13:03:43 -0700
From:	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
To:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Cc:	Nick Piggin <nickpiggin@...oo.com.au>,
	Peter Zijlstra <peterz@...radead.org>,
	Jan Beulich <JBeulich@...ell.com>, Avi Kivity <avi@...hat.com>,
	Xen-devel <xen-devel@...ts.xensource.com>
Subject: [PATCH RFC 03/12] x86/ticketlock: Use C for __ticket_spin_unlock

If we don't need to use a locked inc for unlock, then implement it in C.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
---
 arch/x86/include/asm/spinlock.h |   33 ++++++++++++++++++---------------
 1 files changed, 18 insertions(+), 15 deletions(-)

diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h
index 6711d36..082990a 100644
--- a/arch/x86/include/asm/spinlock.h
+++ b/arch/x86/include/asm/spinlock.h
@@ -33,9 +33,23 @@
  * On PPro SMP or if we are using OOSTORE, we use a locked operation to unlock
  * (PPro errata 66, 92)
  */
-# define UNLOCK_LOCK_PREFIX LOCK_PREFIX
+static __always_inline void __ticket_unlock_release(struct arch_spinlock *lock)
+{
+	if (sizeof(lock->tickets.head) == sizeof(u8))
+		asm (LOCK_PREFIX "incb %0"
+		     : "+m" (lock->tickets.head) : : "memory");
+	else
+		asm (LOCK_PREFIX "incw %0"
+		     : "+m" (lock->tickets.head) : : "memory");
+
+}
 #else
-# define UNLOCK_LOCK_PREFIX
+static __always_inline void __ticket_unlock_release(struct arch_spinlock *lock)
+{
+	barrier();
+	lock->tickets.head++;
+	barrier();
+}
 #endif
 
 /*
@@ -93,14 +107,6 @@ static __always_inline int __ticket_spin_trylock(arch_spinlock_t *lock)
 
 	return tmp;
 }
-
-static __always_inline void __ticket_spin_unlock(arch_spinlock_t *lock)
-{
-	asm volatile(UNLOCK_LOCK_PREFIX "incb %0"
-		     : "+m" (lock->slock)
-		     :
-		     : "memory", "cc");
-}
 #else
 static __always_inline void __ticket_spin_lock(arch_spinlock_t *lock)
 {
@@ -144,15 +150,12 @@ static __always_inline int __ticket_spin_trylock(arch_spinlock_t *lock)
 
 	return tmp;
 }
+#endif
 
 static __always_inline void __ticket_spin_unlock(arch_spinlock_t *lock)
 {
-	asm volatile(UNLOCK_LOCK_PREFIX "incw %0"
-		     : "+m" (lock->slock)
-		     :
-		     : "memory", "cc");
+	__ticket_unlock_release(lock);
 }
-#endif
 
 static inline int __ticket_spin_is_locked(arch_spinlock_t *lock)
 {
-- 
1.7.1.1


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