From 471a3091608cd9546f3c39c8363c0440028fefb1 Mon Sep 17 00:00:00 2001
From: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Date: Tue, 13 Jul 2010 15:14:26 -0700
Subject: [PATCH] --- yaml --- r: 269553 b: refs/heads/master c:
 229855d6f3b40d01a903120c433d75e483a0b06d h: refs/heads/master i:   269551:
 807e7126adc6f8c8f4291900e92afc1bb636c81c v: v3

---
 [refs]                                      |  2 +-
 trunk/arch/x86/include/asm/spinlock.h       | 51 +++++----------------
 trunk/arch/x86/include/asm/spinlock_types.h |  6 ++-
 3 files changed, 17 insertions(+), 42 deletions(-)

diff --git a/[refs] b/[refs]
index 7d671d256d71..351ccd345f12 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 2994488fe5bb721de1ded53af1a2fc41f47f6ddc
+refs/heads/master: 229855d6f3b40d01a903120c433d75e483a0b06d
diff --git a/trunk/arch/x86/include/asm/spinlock.h b/trunk/arch/x86/include/asm/spinlock.h
index b69e0b473de6..f5695eeb83ff 100644
--- a/trunk/arch/x86/include/asm/spinlock.h
+++ b/trunk/arch/x86/include/asm/spinlock.h
@@ -69,60 +69,33 @@ static __always_inline void __ticket_spin_lock(arch_spinlock_t *lock)
 	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;
-
-	asm volatile("movzwl %2, %0\n\t"
-		     "cmpb %h0,%b0\n\t"
-		     "leal 0x100(%" REG_PTR_MODE "0), %1\n\t"
-		     "jne 1f\n\t"
-		     LOCK_PREFIX "cmpxchgw %w1,%2\n\t"
-		     "1:"
-		     "sete %b1\n\t"
-		     "movzbl %b1,%0\n\t"
-		     : "=&a" (tmp), "=&q" (new), "+m" (lock->slock)
-		     :
-		     : "memory", "cc");
+	arch_spinlock_t old, new;
+
+	old.tickets = ACCESS_ONCE(lock->tickets);
+	if (old.tickets.head != old.tickets.tail)
+		return 0;
 
-	return tmp;
+	new.head_tail = old.head_tail + (1 << TICKET_SHIFT);
+
+	/* cmpxchg is a full barrier, so nothing can move before it */
+	return cmpxchg(&lock->head_tail, old.head_tail, new.head_tail) == old.head_tail;
 }
 
+#if (NR_CPUS < 256)
 static __always_inline void __ticket_spin_unlock(arch_spinlock_t *lock)
 {
 	asm volatile(UNLOCK_LOCK_PREFIX "incb %0"
-		     : "+m" (lock->slock)
+		     : "+m" (lock->head_tail)
 		     :
 		     : "memory", "cc");
 }
 #else
-static __always_inline int __ticket_spin_trylock(arch_spinlock_t *lock)
-{
-	unsigned tmp;
-	unsigned new;
-
-	asm volatile("movl %2,%0\n\t"
-		     "movl %0,%1\n\t"
-		     "roll $16, %0\n\t"
-		     "cmpl %0,%1\n\t"
-		     "leal 0x00010000(%" REG_PTR_MODE "0), %1\n\t"
-		     "jne 1f\n\t"
-		     LOCK_PREFIX "cmpxchgl %1,%2\n\t"
-		     "1:"
-		     "sete %b1\n\t"
-		     "movzbl %b1,%0\n\t"
-		     : "=&a" (tmp), "=&q" (new), "+m" (lock->slock)
-		     :
-		     : "memory", "cc");
-
-	return tmp;
-}
-
 static __always_inline void __ticket_spin_unlock(arch_spinlock_t *lock)
 {
 	asm volatile(UNLOCK_LOCK_PREFIX "incw %0"
-		     : "+m" (lock->slock)
+		     : "+m" (lock->head_tail)
 		     :
 		     : "memory", "cc");
 }
diff --git a/trunk/arch/x86/include/asm/spinlock_types.h b/trunk/arch/x86/include/asm/spinlock_types.h
index 1c51bd231e49..8ebd5df7451e 100644
--- a/trunk/arch/x86/include/asm/spinlock_types.h
+++ b/trunk/arch/x86/include/asm/spinlock_types.h
@@ -9,8 +9,10 @@
 
 #if (CONFIG_NR_CPUS < 256)
 typedef u8  __ticket_t;
+typedef u16 __ticketpair_t;
 #else
 typedef u16 __ticket_t;
+typedef u32 __ticketpair_t;
 #endif
 
 #define TICKET_SHIFT	(sizeof(__ticket_t) * 8)
@@ -18,14 +20,14 @@ typedef u16 __ticket_t;
 
 typedef struct arch_spinlock {
 	union {
-		unsigned int slock;
+		__ticketpair_t head_tail;
 		struct __raw_tickets {
 			__ticket_t head, tail;
 		} tickets;
 	};
 } arch_spinlock_t;
 
-#define __ARCH_SPIN_LOCK_UNLOCKED	{ { .slock = 0 } }
+#define __ARCH_SPIN_LOCK_UNLOCKED	{ { 0 } }
 
 #include <asm/rwlock.h>