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Commit f9b94b00 authored by threader's avatar threader Committed by Bernhard Thoben
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BACKPORT: headers: atomic: add atomic_try_cmpxchg as per... 

BACKPORT: headers: atomic: add atomic_try_cmpxchg as per https://patchwork.kernel.org/project/backports/patch/20170908112511.7132-1-johannes@sipsolutions.net
parent f74d4093

include/linux/atomic.h

+49 −0
Original line number Diff line number Diff line
@@ -39,6 +39,55 @@ static inline void __deprecated smp_mb__after_atomic_dec(void) 
}

#endif



/* atomic_cmpxchg_relaxed */

#ifndef atomic_cmpxchg_relaxed

#define  atomic_cmpxchg_relaxed		atomic_cmpxchg

#define  atomic_cmpxchg_acquire		atomic_cmpxchg

#define  atomic_cmpxchg_release		atomic_cmpxchg



#else /* atomic_cmpxchg_relaxed */



#ifndef atomic_cmpxchg_acquire

#define  atomic_cmpxchg_acquire(...)					\

	__atomic_op_acquire(atomic_cmpxchg, __VA_ARGS__)

#endif



#ifndef atomic_cmpxchg_release

#define  atomic_cmpxchg_release(...)					\

	__atomic_op_release(atomic_cmpxchg, __VA_ARGS__)

#endif



#ifndef atomic_cmpxchg

#define  atomic_cmpxchg(...)						\

	__atomic_op_fence(atomic_cmpxchg, __VA_ARGS__)

#endif

#endif /* atomic_cmpxchg_relaxed */



/* these were introduced together, so just a single check is enough */

#ifndef atomic_try_cmpxchg_acquire

#ifndef atomic_try_cmpxchg

#define __atomic_try_cmpxchg(type, _p, _po, _n)				\

({									\

	typeof(_po) __po = (_po);					\

	typeof(*(_po)) __r, __o = *__po;				\

	__r = atomic_cmpxchg##type((_p), __o, (_n));			\

	if (unlikely(__r != __o))					\

		*__po = __r;						\

	likely(__r == __o);						\

})



#define atomic_try_cmpxchg(_p, _po, _n)		__atomic_try_cmpxchg(, _p, _po, _n)

#define atomic_try_cmpxchg_relaxed(_p, _po, _n)	__atomic_try_cmpxchg(_relaxed, _p, _po, _n)

#define atomic_try_cmpxchg_acquire(_p, _po, _n)	__atomic_try_cmpxchg(_acquire, _p, _po, _n)

#define atomic_try_cmpxchg_release(_p, _po, _n)	__atomic_try_cmpxchg(_release, _p, _po, _n)

#else /* atomic_try_cmpxchg */

#define atomic_try_cmpxchg_relaxed	atomic_try_cmpxchg

#define atomic_try_cmpxchg_acquire	atomic_try_cmpxchg

#define atomic_try_cmpxchg_release	atomic_try_cmpxchg

#endif /* atomic_try_cmpxchg */



#endif /* atomic_try_cmpxchg_acquire */



/**

 * atomic_add_unless - add unless the number is already a given value

 * @v: pointer of type atomic_t