sparc32: Implement xchg and atomic_xchg using ATOMIC_HASH locks
Atomicity between xchg and cmpxchg cannot be guaranteed when xchg is
implemented with a swap and cmpxchg is implemented with locks.
Without this, e.g. mcs_spin_lock and mcs_spin_unlock are broken.
Signed-off-by: Andreas Larsson <andreas@gaisler.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/arch/sparc/lib/atomic32.c b/arch/sparc/lib/atomic32.c
index a7c418a..71cd65a 100644
--- a/arch/sparc/lib/atomic32.c
+++ b/arch/sparc/lib/atomic32.c
@@ -45,6 +45,19 @@
#undef ATOMIC_OP
+int atomic_xchg(atomic_t *v, int new)
+{
+ int ret;
+ unsigned long flags;
+
+ spin_lock_irqsave(ATOMIC_HASH(v), flags);
+ ret = v->counter;
+ v->counter = new;
+ spin_unlock_irqrestore(ATOMIC_HASH(v), flags);
+ return ret;
+}
+EXPORT_SYMBOL(atomic_xchg);
+
int atomic_cmpxchg(atomic_t *v, int old, int new)
{
int ret;
@@ -137,3 +150,17 @@
return (unsigned long)prev;
}
EXPORT_SYMBOL(__cmpxchg_u32);
+
+unsigned long __xchg_u32(volatile u32 *ptr, u32 new)
+{
+ unsigned long flags;
+ u32 prev;
+
+ spin_lock_irqsave(ATOMIC_HASH(ptr), flags);
+ prev = *ptr;
+ *ptr = new;
+ spin_unlock_irqrestore(ATOMIC_HASH(ptr), flags);
+
+ return (unsigned long)prev;
+}
+EXPORT_SYMBOL(__xchg_u32);