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>

1 files changed, 27 insertions, 0 deletions

diff --git a/arch/sparc/lib/atomic32.c b/arch/sparc/lib/atomic32.c
index a7c418ac26af..71cd65ab200c 100644
--- a/arch/sparc/lib/atomic32.c
+++ b/arch/sparc/lib/atomic32.c
@@ -45,6 +45,19 @@ ATOMIC_OP(add, +=)
 
 #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 @@ unsigned long __cmpxchg_u32(volatile u32 *ptr, u32 old, u32 new)
         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);