From 4a6dae6d382e9edf3ff440b819e554ed706359bc Mon Sep 17 00:00:00 2001 From: Nick Piggin Date: Sun, 13 Nov 2005 16:07:24 -0800 Subject: [PATCH] atomic: cmpxchg Introduce an atomic_cmpxchg operation. Signed-off-by: Nick Piggin Cc: "Paul E. McKenney" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/sparc/lib/atomic32.c | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-) (limited to 'arch/sparc/lib') diff --git a/arch/sparc/lib/atomic32.c b/arch/sparc/lib/atomic32.c index 2e64e8c..be46f65 100644 --- a/arch/sparc/lib/atomic32.c +++ b/arch/sparc/lib/atomic32.c @@ -37,17 +37,28 @@ int __atomic_add_return(int i, atomic_t *v) spin_unlock_irqrestore(ATOMIC_HASH(v), flags); return ret; } +EXPORT_SYMBOL(__atomic_add_return); -void atomic_set(atomic_t *v, int i) +int atomic_cmpxchg(atomic_t *v, int old, int new) { + int ret; unsigned long flags; - spin_lock_irqsave(ATOMIC_HASH(v), flags); - v->counter = i; + spin_lock_irqsave(ATOMIC_HASH(v), flags); + ret = v->counter; + if (likely(ret == old)) + v->counter = new; spin_unlock_irqrestore(ATOMIC_HASH(v), flags); + return ret; } -EXPORT_SYMBOL(__atomic_add_return); -EXPORT_SYMBOL(atomic_set); +void atomic_set(atomic_t *v, int i) +{ + unsigned long flags; + spin_lock_irqsave(ATOMIC_HASH(v), flags); + v->counter = i; + spin_unlock_irqrestore(ATOMIC_HASH(v), flags); +} +EXPORT_SYMBOL(atomic_set); -- cgit v1.1