[PATCH][2.6] Allow x86_64 to reenable interrupts on contention

[Zwane Mwaikambo]

This is a follow up to the previous patches for ia64 and i386, it will
allow x86_64 to reenable interrupts during contested locks depending on
previous interrupt enable status. It has been runtime and compile tested
on UP and 2x SMP Linux-tiny/x86_64.

Signed-off-by: Zwane Mwaikambo <zwane@xxxxxxxxxxx>

--- linux-2.6-amd64/include/asm-x86_64/spinlock.h.orig	2004-07-27 03:32:18.689949016 -0400
+++ linux-2.6-amd64/include/asm-x86_64/spinlock.h	2004-07-27 03:45:19.610231088 -0400
@@ -41,7 +41,6 @@ typedef struct {

 #define spin_is_locked(x)	(*(volatile signed char *)(&(x)->lock) <= 0)
 #define spin_unlock_wait(x)	do { barrier(); } while(spin_is_locked(x))
-#define _raw_spin_lock_flags(lock, flags) _raw_spin_lock(lock)

 #define spin_lock_string \
 	"\n1:\t" \
@@ -55,6 +54,23 @@ typedef struct {
 	"jmp 1b\n" \
 	LOCK_SECTION_END

+#define 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
+
 /*
  * This works. Despite all the confusion.
  * (except on PPro SMP or if we are using OOSTORE)
@@ -125,6 +141,20 @@ printk("eip: %p\n", &&here);
 		:"=m" (lock->lock) : : "memory");
 }

+static inline void _raw_spin_lock_flags (spinlock_t *lock, unsigned long flags)
+{
+#ifdef CONFIG_DEBUG_SPINLOCK
+	__label__ here;
+here:
+	if (unlikely(lock->magic != SPINLOCK_MAGIC)) {
+		printk("eip: %p\n", &&here);
+		BUG();
+	}
+#endif
+	__asm__ __volatile__(spin_lock_string_flags
+		:"=m" (lock->lock) : "r" (flags) : "memory");
+}
+

 /*
  * Read-write spinlocks, allowing multiple readers
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/