locking/atomic, arch/xtensa: Implement atomic_fetch_{add,sub,and,or,xor}()

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@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Chris Zankel <chris@zankel.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-xtensa@linux-xtensa.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/xtensa/include/asm/atomic.h b/arch/xtensa/include/asm/atomic.h
index fd8017c..d95a8aa 100644 (file)
--- a/arch/xtensa/include/asm/atomic.h
+++ b/arch/xtensa/include/asm/atomic.h
@@ -98,6 +98,26 @@ static inline int atomic_##op##_return(int i, atomic_t * v)          \
        return result;                                                  \
 }
 
+#define ATOMIC_FETCH_OP(op)                                            \
+static inline int atomic_fetch_##op(int i, atomic_t * v)               \
+{                                                                      \
+       unsigned long tmp;                                              \
+       int result;                                                     \
+                                                                       \
+       __asm__ __volatile__(                                           \
+                       "1:     l32i    %1, %3, 0\n"                    \
+                       "       wsr     %1, scompare1\n"                \
+                       "       " #op " %0, %1, %2\n"                   \
+                       "       s32c1i  %0, %3, 0\n"                    \
+                       "       bne     %0, %1, 1b\n"                   \
+                       : "=&a" (result), "=&a" (tmp)                   \
+                       : "a" (i), "a" (v)                              \
+                       : "memory"                                      \
+                       );                                              \
+                                                                       \
+       return result;                                                  \
+}
+
 #else /* XCHAL_HAVE_S32C1I */
 
 #define ATOMIC_OP(op)                                                  \
@@ -138,18 +158,44 @@ static inline int atomic_##op##_return(int i, atomic_t * v)               \
        return vval;                                                    \
 }
 
+#define ATOMIC_FETCH_OP(op)                                            \
+static inline int atomic_fetch_##op(int i, atomic_t * v)               \
+{                                                                      \
+       unsigned int tmp, vval;                                         \
+                                                                       \
+       __asm__ __volatile__(                                           \
+                       "       rsil    a15,"__stringify(TOPLEVEL)"\n"  \
+                       "       l32i    %0, %3, 0\n"                    \
+                       "       " #op " %1, %0, %2\n"                   \
+                       "       s32i    %1, %3, 0\n"                    \
+                       "       wsr     a15, ps\n"                      \
+                       "       rsync\n"                                \
+                       : "=&a" (vval), "=&a" (tmp)                     \
+                       : "a" (i), "a" (v)                              \
+                       : "a15", "memory"                               \
+                       );                                              \
+                                                                       \
+       return vval;                                                    \
+}
+
 #endif /* XCHAL_HAVE_S32C1I */
 
-#define ATOMIC_OPS(op) ATOMIC_OP(op) ATOMIC_OP_RETURN(op)
+#define ATOMIC_OPS(op) ATOMIC_OP(op) ATOMIC_FETCH_OP(op) ATOMIC_OP_RETURN(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