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Commit e39d88ea authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
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locking/atomic, arch/m68k: 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: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
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-m68k@lists.linux-m68k.org
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent f6493705

arch/m68k/include/asm/atomic.h

+49 −4
Original line number Diff line number Diff line
@@ -38,6 +38,13 @@ static inline void atomic_##op(int i, atomic_t *v) \ 


#ifdef CONFIG_RMW_INSNS



/*

 * Am I reading these CAS loops right in that %2 is the old value and the first

 * iteration uses an uninitialized value?

 *

 * Would it not make sense to add: tmp = atomic_read(v); to avoid this?

 */



#define ATOMIC_OP_RETURN(op, c_op, asm_op)				\

static inline int atomic_##op##_return(int i, atomic_t *v)		\

{									\
@@ -53,6 +60,21 @@ static inline int atomic_##op##_return(int i, atomic_t *v) \ 
	return t;							\

}



#define ATOMIC_FETCH_OP(op, c_op, asm_op)				\

static inline int atomic_fetch_##op(int i, atomic_t *v)			\

{									\

	int t, tmp;							\

									\

	__asm__ __volatile__(						\

			"1:	movel %2,%1\n"				\

			"	" #asm_op "l %3,%1\n"			\

			"	casl %2,%1,%0\n"			\

			"	jne 1b"					\

			: "+m" (*v), "=&d" (t), "=&d" (tmp)		\

			: "g" (i), "2" (atomic_read(v)));		\

	return tmp;							\

}



#else



#define ATOMIC_OP_RETURN(op, c_op, asm_op)				\
@@ -68,20 +90,43 @@ static inline int atomic_##op##_return(int i, atomic_t * v) \ 
	return t;							\

}



#define ATOMIC_FETCH_OP(op, c_op, asm_op)				\

static inline int atomic_fetch_##op(int i, atomic_t * v)		\

{									\

	unsigned long flags;						\

	int t;								\

									\

	local_irq_save(flags);						\

	t = v->counter;							\

	v->counter c_op i;						\

	local_irq_restore(flags);					\

									\

	return t;							\

}



#endif /* CONFIG_RMW_INSNS */



#define ATOMIC_OPS(op, c_op, asm_op)					\

	ATOMIC_OP(op, c_op, asm_op)					\

	ATOMIC_OP_RETURN(op, c_op, asm_op)

	ATOMIC_OP_RETURN(op, c_op, asm_op)				\

	ATOMIC_FETCH_OP(op, c_op, asm_op)



ATOMIC_OPS(add, +=, add)

ATOMIC_OPS(sub, -=, sub)



ATOMIC_OP(and, &=, and)

ATOMIC_OP(or, |=, or)

ATOMIC_OP(xor, ^=, eor)

#undef ATOMIC_OPS

#define ATOMIC_OPS(op, c_op, asm_op)					\

	ATOMIC_OP(op, c_op, asm_op)					\

	ATOMIC_FETCH_OP(op, c_op, asm_op)



#define atomic_fetch_or atomic_fetch_or



ATOMIC_OPS(and, &=, and)

ATOMIC_OPS(or, |=, or)

ATOMIC_OPS(xor, ^=, eor)



#undef ATOMIC_OPS

#undef ATOMIC_FETCH_OP

#undef ATOMIC_OP_RETURN

#undef ATOMIC_OP