Commit 4be7dd39 authored Apr 18, 2016 by Peter Zijlstra Committed by Ingo Molnar Jun 16, 2016

locking/atomic, arch/hexagon: 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: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Richard Kuo <rkuo@codeaurora.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: linux-hexagon@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 0c074cbc

arch/hexagon/include/asm/atomic.h

+28 −5

Original line number	Diff line number	Diff line
		@@ -127,16 +127,39 @@ static inline int atomic_##op##_return(int i, atomic_t *v) \
		return output; \
		}

		#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 output, val; \
		\
		__asm__ __volatile__ ( \
		"1: %0 = memw_locked(%2);\n" \
		" %1 = "#op "(%0,%3);\n" \
		" memw_locked(%2,P3)=%1;\n" \
		" if !P3 jump 1b;\n" \
		: "=&r" (output), "=&r" (val) \
		: "r" (&v->counter), "r" (i) \
		: "memory", "p3" \
		); \
		return output; \
		}

		#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