ARM: 7632/1: spinlock: avoid exclusive accesses on unlock() path
When unlocking a spinlock, all we need to do is increment the owner
field of the lock. Since only one CPU can be performing an unlock()
operation for a given lock, this doesn't need to be exclusive.
This patch simplifies arch_spin_unlock to use non-exclusive accesses
when updating the owner field of the lock.
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/include/asm/spinlock.h b/arch/arm/include/asm/spinlock.h
index b4ca707..6220e9f 100644
--- a/arch/arm/include/asm/spinlock.h
+++ b/arch/arm/include/asm/spinlock.h
@@ -119,22 +119,8 @@
static inline void arch_spin_unlock(arch_spinlock_t *lock)
{
- unsigned long tmp;
- u32 slock;
-
smp_mb();
-
- __asm__ __volatile__(
-" mov %1, #1\n"
-"1: ldrex %0, [%2]\n"
-" uadd16 %0, %0, %1\n"
-" strex %1, %0, [%2]\n"
-" teq %1, #0\n"
-" bne 1b"
- : "=&r" (slock), "=&r" (tmp)
- : "r" (&lock->slock)
- : "cc");
-
+ lock->tickets.owner++;
dsb_sev();
}