Fix x86_64 _spin_lock_irqsave()

From: Edward Falk <efalk@google.com>
Add spin_lock_string_flags and _raw_spin_lock_flags() to 
asm-x86_64/spinlock.h so that _spin_lock_irqsave() has the same 
semantics on x86_64 as it does on i386 and does *not* have interrupts 
disabled while it is waiting for the lock.

This fix is courtesy of Michael Davidson

Signed-off-by: Andi Kleen <ak@suse.de>

---
 include/asm-x86_64/spinlock.h |   26 ++++++++++++++++++++++++--
 1 files changed, 24 insertions(+), 2 deletions(-)

Index: linux/include/asm-x86_64/spinlock.h
===================================================================
--- linux.orig/include/asm-x86_64/spinlock.h
+++ linux/include/asm-x86_64/spinlock.h
@@ -33,6 +33,23 @@
 #define __raw_spin_lock_string_up \
 	"\n\tdecl %0"
 
+#define __raw_spin_lock_string_flags \
+	"\n1:\t" \
+	"lock ; decb %0\n\t" \
+	"js 2f\n\t" \
+	LOCK_SECTION_START("") \
+	"2:\t" \
+	"test $0x200, %1\n\t" \
+	"jz 3f\n\t" \
+	"sti\n\t" \
+	"3:\t" \
+	"rep;nop\n\t" \
+	"cmpb $0, %0\n\t" \
+	"jle 3b\n\t" \
+	"cli\n\t" \
+	"jmp 1b\n" \
+	LOCK_SECTION_END
+
 #define __raw_spin_unlock_string \
 	"movl $1,%0" \
 		:"=m" (lock->slock) : : "memory"
@@ -45,8 +62,6 @@ static inline void __raw_spin_lock(raw_s
 		"=m" (lock->slock) : : "memory");
 }
 
-#define __raw_spin_lock_flags(lock, flags) __raw_spin_lock(lock)
-
 static inline int __raw_spin_trylock(raw_spinlock_t *lock)
 {
 	int oldval;
@@ -59,6 +74,13 @@ static inline int __raw_spin_trylock(raw
 	return oldval > 0;
 }
 
+static inline void __raw_spin_lock_flags(raw_spinlock_t *lock, unsigned long flags)
+{
+	__asm__ __volatile__(
+		__raw_spin_lock_string_flags
+		:"=m" (lock->slock) : "r" (flags) : "memory");
+}
+
 static inline void __raw_spin_unlock(raw_spinlock_t *lock)
 {
 	__asm__ __volatile__(