Implement FETCH-OP atomic primitives, these are very similar to the
existing OP-RETURN primitives we already have, except they return the
value of the atomic variable _before_ modification.
This is especially useful for irreversible operations -- such as
bitops (because it becomes impossible to reconstruct the state prior
to modification).
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
arch/mn10300/include/asm/atomic.h | 35 +++++++++++++++++++++++++++++++----
1 file changed, 31 insertions(+), 4 deletions(-)
--- a/arch/mn10300/include/asm/atomic.h
+++ b/arch/mn10300/include/asm/atomic.h
@@ -84,16 +84,43 @@ static inline int atomic_##op##_return(i
return retval; \
}
-#define ATOMIC_OPS(op) ATOMIC_OP(op) ATOMIC_OP_RETURN(op)
+#define ATOMIC_FETCH_OP(op) \
+static inline int atomic_fetch_##op(int i, atomic_t *v) \
+{ \
+ int retval, status; \
+ \
+ asm volatile( \
+ "1: mov %4,(_AAR,%3) \n" \
+ " mov (_ADR,%3),%1 \n" \
+ " mov %1,%0 \n" \
+ " " #op " %5,%0 \n" \
+ " mov %0,(_ADR,%3) \n" \
+ " mov (_ADR,%3),%0 \n" /* flush */ \
+ " mov (_ASR,%3),%0 \n" \
+ " or %0,%0 \n" \
+ " bne 1b \n" \
+ : "=&r"(status), "=&r"(retval), "=m"(v->counter) \
+ : "a"(ATOMIC_OPS_BASE_ADDR), "r"(&v->counter), "r"(i) \
+ : "memory", "cc"); \
+ return retval; \
+}
+
+#define ATOMIC_OPS(op) ATOMIC_OP(op) ATOMIC_OP_RETURN(op) ATOMIC_FETCH_OP(op)
ATOMIC_OPS(add)
ATOMIC_OPS(sub)
-ATOMIC_OP(and)
-ATOMIC_OP(or)
-ATOMIC_OP(xor)
+#undef ATOMIC_OPS
+#define ATOMIC_OPS(op) ATOMIC_OP(op) ATOMIC_FETCH_OP(op)
+
+#define atomic_fetch_or atomic_fetch_or
+
+ATOMIC_OPS(and)
+ATOMIC_OPS(or)
+ATOMIC_OPS(xor)
#undef ATOMIC_OPS
+#undef ATOMIC_FETCH_OP
#undef ATOMIC_OP_RETURN
#undef ATOMIC_OP
--
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