Commit e79bee24 authored by Shaohua Li's avatar Shaohua Li Committed by Linus Torvalds
Browse files

atomic: implement generic atomic_dec_if_positive() 



The x86 implementation of atomic_dec_if_positive is quite generic, so make
it available to all architectures.

This is needed for "swap: add a simple detector for inappropriate swapin
readahead".

[akpm@linux-foundation.org: do the "#define foo foo" trick in the conventional manner]
Signed-off-by: default avatarShaohua Li <shli@fusionio.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Rik van Riel <riel@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Michal Simek <monstr@monstr.eu>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 435b405c

arch/microblaze/include/asm/atomic.h

+1 −0
Original line number Diff line number Diff line
@@ -22,5 +22,6 @@ static inline int atomic_dec_if_positive(atomic_t *v) 


	return res;

}

#define atomic_dec_if_positive atomic_dec_if_positive



#endif /* _ASM_MICROBLAZE_ATOMIC_H */

arch/powerpc/include/asm/atomic.h

+1 −0
Original line number Diff line number Diff line
@@ -268,6 +268,7 @@ static __inline__ int atomic_dec_if_positive(atomic_t *v) 


	return t;

}

#define atomic_dec_if_positive atomic_dec_if_positive



#define smp_mb__before_atomic_dec()     smp_mb()

#define smp_mb__after_atomic_dec()      smp_mb()

arch/x86/include/asm/atomic.h

+0 −24
Original line number Diff line number Diff line
@@ -240,30 +240,6 @@ static inline int __atomic_add_unless(atomic_t *v, int a, int u) 
	return c;

}





/*

 * atomic_dec_if_positive - decrement by 1 if old value positive

 * @v: pointer of type atomic_t

 *

 * The function returns the old value of *v minus 1, even if

 * the atomic variable, v, was not decremented.

 */

static inline int atomic_dec_if_positive(atomic_t *v)

{

	int c, old, dec;

	c = atomic_read(v);

	for (;;) {

		dec = c - 1;

		if (unlikely(dec < 0))

			break;

		old = atomic_cmpxchg((v), c, dec);

		if (likely(old == c))

			break;

		c = old;

	}

	return dec;

}



/**

 * atomic_inc_short - increment of a short integer

 * @v: pointer to type int

include/linux/atomic.h

+25 −0
Original line number Diff line number Diff line
@@ -86,6 +86,31 @@ static inline int atomic_dec_unless_positive(atomic_t *p) 
}

#endif



/*

 * atomic_dec_if_positive - decrement by 1 if old value positive

 * @v: pointer of type atomic_t

 *

 * The function returns the old value of *v minus 1, even if

 * the atomic variable, v, was not decremented.

 */

#ifndef atomic_dec_if_positive

static inline int atomic_dec_if_positive(atomic_t *v)

{

	int c, old, dec;

	c = atomic_read(v);

	for (;;) {

		dec = c - 1;

		if (unlikely(dec < 0))

			break;

		old = atomic_cmpxchg((v), c, dec);

		if (likely(old == c))

			break;

		c = old;

	}

	return dec;

}

#endif



#ifndef CONFIG_ARCH_HAS_ATOMIC_OR

static inline void atomic_or(int i, atomic_t *v)

{

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