Commit eccc2da8 authored by Mark Rutland's avatar Mark Rutland Committed by Ingo Molnar
Browse files

atomics/treewide: Make atomic_fetch_add_unless() optional 



Several architectures these have a near-identical implementation based
on atomic_read() and atomic_cmpxchg() which we can instead define in
<linux/atomic.h>, so let's do so, using something close to the existing
x86 implementation with try_cmpxchg().

Where an architecture provides its own atomic_fetch_add_unless(), it
must define a preprocessor symbol for it. The instrumented atomics are
updated accordingly.

Note that arch/arc's existing atomic_fetch_add_unless() had redundant
barriers, as these are already present in its atomic_cmpxchg()
implementation.

There should be no functional change as a result of this patch.

Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
Reviewed-by: default avatarGeert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: default avatarWill Deacon <will.deacon@arm.com>
Acked-by: default avatarGeert Uytterhoeven <geert@linux-m68k.org>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: default avatarPalmer Dabbelt <palmer@sifive.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vineet Gupta <vgupta@synopsys.com>
Link: https://lore.kernel.org/lkml/20180621121321.4761-7-mark.rutland@arm.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent bef82820

arch/alpha/include/asm/atomic.h

+1 −1
Original line number Diff line number Diff line
@@ -235,7 +235,7 @@ static __inline__ int atomic_fetch_add_unless(atomic_t *v, int a, int u) 
	smp_mb();

	return old;

}



#define atomic_fetch_add_unless atomic_fetch_add_unless



/**

 * atomic64_add_unless - add unless the number is a given value

arch/arc/include/asm/atomic.h

+0 −28
Original line number Diff line number Diff line
@@ -308,34 +308,6 @@ ATOMIC_OPS(xor, ^=, CTOP_INST_AXOR_DI_R2_R2_R3) 
#undef ATOMIC_OP_RETURN

#undef ATOMIC_OP



/**

 * atomic_fetch_add_unless - add unless the number is a given value

 * @v: pointer of type atomic_t

 * @a: the amount to add to v...

 * @u: ...unless v is equal to u.

 *

 * Atomically adds @a to @v, so long as it was not @u.

 * Returns the old value of @v

 */

#define atomic_fetch_add_unless(v, a, u)					\

({									\

	int c, old;							\

									\

	/*								\

	 * Explicit full memory barrier needed before/after as		\

	 * LLOCK/SCOND thmeselves don't provide any such semantics	\

	 */								\

	smp_mb();							\

									\

	c = atomic_read(v);						\

	while (c != (u) && (old = atomic_cmpxchg((v), c, c + (a))) != c)\

		c = old;						\

									\

	smp_mb();							\

									\

	c;								\

})



#define atomic_inc(v)			atomic_add(1, v)

#define atomic_dec(v)			atomic_sub(1, v)

arch/arm/include/asm/atomic.h

+1 −10
Original line number Diff line number Diff line
@@ -156,6 +156,7 @@ static inline int atomic_fetch_add_unless(atomic_t *v, int a, int u) 


	return oldval;

}

#define atomic_fetch_add_unless		atomic_fetch_add_unless



#else /* ARM_ARCH_6 */
@@ -215,16 +216,6 @@ static inline int atomic_cmpxchg(atomic_t *v, int old, int new) 
	return ret;

}



static inline int atomic_fetch_add_unless(atomic_t *v, int a, int u)

{

	int c, old;



	c = atomic_read(v);

	while (c != u && (old = atomic_cmpxchg((v), c, c + a)) != c)

		c = old;

	return c;

}



#endif /* __LINUX_ARM_ARCH__ */



#define ATOMIC_OPS(op, c_op, asm_op)					\

arch/arm64/include/asm/atomic.h

+0 −1
Original line number Diff line number Diff line
@@ -125,7 +125,6 @@ 
#define atomic_dec_and_test(v)		(atomic_dec_return(v) == 0)

#define atomic_sub_and_test(i, v)	(atomic_sub_return((i), (v)) == 0)

#define atomic_add_negative(i, v)	(atomic_add_return((i), (v)) < 0)

#define atomic_fetch_add_unless(v, a, u)	___atomic_add_unless(v, a, u,)

#define atomic_andnot			atomic_andnot



/*

arch/h8300/include/asm/atomic.h

+1 −0
Original line number Diff line number Diff line
@@ -106,5 +106,6 @@ static inline int atomic_fetch_add_unless(atomic_t *v, int a, int u) 
	arch_local_irq_restore(flags);

	return ret;

}

#define atomic_fetch_add_unless		atomic_fetch_add_unless



#endif /* __ARCH_H8300_ATOMIC __ */

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