linux-kernel - [tip:x86/spinlocks] x86, ticketlock: Make __ticket_spin

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Message-ID: <tip-65bd26616b53c5dfab162f18c34ec57ddb682a00@git.kernel.org>
Date:	Fri, 22 Jul 2011 19:57:25 GMT
From:	tip-bot for Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	tglx@...utronix.de, hpa@...ux.intel.com,
	jeremy.fitzhardinge@...rix.com
Subject: [tip:x86/spinlocks] x86, ticketlock: Make __ticket_spin_lock common

Commit-ID:  65bd26616b53c5dfab162f18c34ec57ddb682a00
Gitweb:     http://git.kernel.org/tip/65bd26616b53c5dfab162f18c34ec57ddb682a00
Author:     Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
AuthorDate: Thu, 23 Jun 2011 18:19:17 -0700
Committer:  H. Peter Anvin <hpa@...ux.intel.com>
CommitDate: Fri, 22 Jul 2011 11:18:44 -0700

x86, ticketlock: Make __ticket_spin_lock common

Aside from the particular form of the xadd instruction, they're identical.
So factor out the xadd and use common code for the rest.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
Link: http://lkml.kernel.org/r/11b6893703912054024bdb60251ed944f31cbafe.1308878118.git.jeremy.fitzhardinge@citrix.com
Signed-off-by: H. Peter Anvin <hpa@...ux.intel.com>
---
 arch/x86/include/asm/spinlock.h |   42 ++++++++++++++++++--------------------
 1 files changed, 20 insertions(+), 22 deletions(-)

diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h
index 078319e..a0e26c8 100644
--- a/arch/x86/include/asm/spinlock.h
+++ b/arch/x86/include/asm/spinlock.h
@@ -67,13 +67,27 @@ static __always_inline void __ticket_unlock_release(struct arch_spinlock *lock)
  * save some instructions and make the code more elegant. There really isn't
  * much between them in performance though, especially as locks are out of line.
  */
-#if (NR_CPUS < 256)
-static __always_inline void __ticket_spin_lock(arch_spinlock_t *lock)
+static __always_inline struct __raw_tickets __ticket_spin_claim(struct arch_spinlock *lock)
 {
-	register struct __raw_tickets inc = { .tail = 1 };
+	register struct __raw_tickets tickets = { .tail = 1 };
+
+	if (sizeof(lock->tickets.head) == sizeof(u8))
+		asm volatile (LOCK_PREFIX "xaddw %w0, %1\n"
+			      : "+r" (tickets), "+m" (lock->tickets)
+			      : : "memory", "cc");
+	else
+		asm volatile (LOCK_PREFIX "xaddl %0, %1\n"
+			     : "+r" (tickets), "+m" (lock->tickets)
+			     : : "memory", "cc");
 
-	asm volatile (LOCK_PREFIX "xaddw %w0, %1\n"
-		      : "+r" (inc), "+m" (lock->tickets) : : "memory", "cc");
+	return tickets;
+}
+
+static __always_inline void __ticket_spin_lock(struct arch_spinlock *lock)
+{
+	register struct __raw_tickets inc;
+
+	inc = __ticket_spin_claim(lock);
 
 	for (;;) {
 		if (inc.head == inc.tail)
@@ -84,6 +98,7 @@ static __always_inline void __ticket_spin_lock(arch_spinlock_t *lock)
 out:	barrier();		/* make sure nothing creeps before the lock is taken */
 }
 
+#if (NR_CPUS < 256)
 static __always_inline int __ticket_spin_trylock(arch_spinlock_t *lock)
 {
 	unsigned int tmp, new;
@@ -103,23 +118,6 @@ static __always_inline int __ticket_spin_trylock(arch_spinlock_t *lock)
 	return tmp;
 }
 #else
-static __always_inline void __ticket_spin_lock(arch_spinlock_t *lock)
-{
-	register struct __raw_tickets inc = { .tail = 1 };
-
-	asm volatile(LOCK_PREFIX "xaddl %0, %1\n\t"
-		     : "+r" (inc), "+m" (lock->tickets)
-		     : : "memory", "cc");
-
-	for (;;) {
-		if (inc.head == inc.tail)
-			goto out;
-		cpu_relax();
-		inc.head = ACCESS_ONCE(lock->tickets.head);
-	}
-out:	barrier();		/* make sure nothing creeps before the lock is taken */
-}
-
 static __always_inline int __ticket_spin_trylock(arch_spinlock_t *lock)
 {
 	unsigned tmp;
--
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