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Commit 56c08e6d authored by Boqun Feng's avatar Boqun Feng Committed by Michael Ellerman
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powerpc: atomic: Implement acquire/release/relaxed variants for cmpxchg 



Implement cmpxchg{,64}_relaxed and atomic{,64}_cmpxchg_relaxed, based on
which _release variants can be built.

To avoid superfluous barriers in _acquire variants, we implement these
operations with assembly code rather use __atomic_op_acquire() to build
them automatically.

For the same reason, we keep the assembly implementation of fully
ordered cmpxchg operations.

However, we don't do the similar for _release, because that will require
putting barriers in the middle of ll/sc loops, which is probably a bad
idea.

Note cmpxchg{,64}_relaxed and atomic{,64}_cmpxchg_relaxed are not
compiler barriers.

Signed-off-by: default avatarBoqun Feng <boqun.feng@gmail.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 26760fc1

arch/powerpc/include/asm/atomic.h

+10 −0
Original line number Original line Diff line number Diff line
@@ -176,6 +176,11 @@ static __inline__ int atomic_dec_return_relaxed(atomic_t *v) 
#define atomic_dec_return_relaxed atomic_dec_return_relaxed

#define atomic_dec_return_relaxed atomic_dec_return_relaxed





#define atomic_cmpxchg(v, o, n) (cmpxchg(&((v)->counter), (o), (n)))

#define atomic_cmpxchg(v, o, n) (cmpxchg(&((v)->counter), (o), (n)))

#define atomic_cmpxchg_relaxed(v, o, n) \

	cmpxchg_relaxed(&((v)->counter), (o), (n))

#define atomic_cmpxchg_acquire(v, o, n) \

	cmpxchg_acquire(&((v)->counter), (o), (n))



#define atomic_xchg(v, new) (xchg(&((v)->counter), new))

#define atomic_xchg(v, new) (xchg(&((v)->counter), new))

#define atomic_xchg_relaxed(v, new) xchg_relaxed(&((v)->counter), (new))

#define atomic_xchg_relaxed(v, new) xchg_relaxed(&((v)->counter), (new))
@@ -444,6 +449,11 @@ static __inline__ long atomic64_dec_if_positive(atomic64_t *v) 
}

}





#define atomic64_cmpxchg(v, o, n) (cmpxchg(&((v)->counter), (o), (n)))

#define atomic64_cmpxchg(v, o, n) (cmpxchg(&((v)->counter), (o), (n)))

#define atomic64_cmpxchg_relaxed(v, o, n) \

	cmpxchg_relaxed(&((v)->counter), (o), (n))

#define atomic64_cmpxchg_acquire(v, o, n) \

	cmpxchg_acquire(&((v)->counter), (o), (n))



#define atomic64_xchg(v, new) (xchg(&((v)->counter), new))

#define atomic64_xchg(v, new) (xchg(&((v)->counter), new))

#define atomic64_xchg_relaxed(v, new) xchg_relaxed(&((v)->counter), (new))

#define atomic64_xchg_relaxed(v, new) xchg_relaxed(&((v)->counter), (new))

arch/powerpc/include/asm/cmpxchg.h

+148 −1
Original line number Original line Diff line number Diff line
@@ -181,6 +181,56 @@ __cmpxchg_u32_local(volatile unsigned int *p, unsigned long old, 
	return prev;

	return prev;

}

}





static __always_inline unsigned long

__cmpxchg_u32_relaxed(u32 *p, unsigned long old, unsigned long new)

{

	unsigned long prev;



	__asm__ __volatile__ (

"1:	lwarx	%0,0,%2		# __cmpxchg_u32_relaxed\n"

"	cmpw	0,%0,%3\n"

"	bne-	2f\n"

	PPC405_ERR77(0, %2)

"	stwcx.	%4,0,%2\n"

"	bne-	1b\n"

"2:"

	: "=&r" (prev), "+m" (*p)

	: "r" (p), "r" (old), "r" (new)

	: "cc");



	return prev;

}



/*

 * cmpxchg family don't have order guarantee if cmp part fails, therefore we

 * can avoid superfluous barriers if we use assembly code to implement

 * cmpxchg() and cmpxchg_acquire(), however we don't do the similar for

 * cmpxchg_release() because that will result in putting a barrier in the

 * middle of a ll/sc loop, which is probably a bad idea. For example, this

 * might cause the conditional store more likely to fail.

 */

static __always_inline unsigned long

__cmpxchg_u32_acquire(u32 *p, unsigned long old, unsigned long new)

{

	unsigned long prev;



	__asm__ __volatile__ (

"1:	lwarx	%0,0,%2		# __cmpxchg_u32_acquire\n"

"	cmpw	0,%0,%3\n"

"	bne-	2f\n"

	PPC405_ERR77(0, %2)

"	stwcx.	%4,0,%2\n"

"	bne-	1b\n"

	PPC_ACQUIRE_BARRIER

	"\n"

"2:"

	: "=&r" (prev), "+m" (*p)

	: "r" (p), "r" (old), "r" (new)

	: "cc", "memory");



	return prev;

}



#ifdef CONFIG_PPC64

#ifdef CONFIG_PPC64

static __always_inline unsigned long

static __always_inline unsigned long

__cmpxchg_u64(volatile unsigned long *p, unsigned long old, unsigned long new)

__cmpxchg_u64(volatile unsigned long *p, unsigned long old, unsigned long new)
@@ -224,6 +274,46 @@ __cmpxchg_u64_local(volatile unsigned long *p, unsigned long old, 




	return prev;

	return prev;

}

}



static __always_inline unsigned long

__cmpxchg_u64_relaxed(u64 *p, unsigned long old, unsigned long new)

{

	unsigned long prev;



	__asm__ __volatile__ (

"1:	ldarx	%0,0,%2		# __cmpxchg_u64_relaxed\n"

"	cmpd	0,%0,%3\n"

"	bne-	2f\n"

"	stdcx.	%4,0,%2\n"

"	bne-	1b\n"

"2:"

	: "=&r" (prev), "+m" (*p)

	: "r" (p), "r" (old), "r" (new)

	: "cc");



	return prev;

}



static __always_inline unsigned long

__cmpxchg_u64_acquire(u64 *p, unsigned long old, unsigned long new)

{

	unsigned long prev;



	__asm__ __volatile__ (

"1:	ldarx	%0,0,%2		# __cmpxchg_u64_acquire\n"

"	cmpd	0,%0,%3\n"

"	bne-	2f\n"

"	stdcx.	%4,0,%2\n"

"	bne-	1b\n"

	PPC_ACQUIRE_BARRIER

	"\n"

"2:"

	: "=&r" (prev), "+m" (*p)

	: "r" (p), "r" (old), "r" (new)

	: "cc", "memory");



	return prev;

}

#endif

#endif





/* This function doesn't exist, so you'll get a linker error

/* This function doesn't exist, so you'll get a linker error
@@ -262,6 +352,37 @@ __cmpxchg_local(volatile void *ptr, unsigned long old, unsigned long new, 
	return old;

	return old;

}

}





static __always_inline unsigned long

__cmpxchg_relaxed(void *ptr, unsigned long old, unsigned long new,

		  unsigned int size)

{

	switch (size) {

	case 4:

		return __cmpxchg_u32_relaxed(ptr, old, new);

#ifdef CONFIG_PPC64

	case 8:

		return __cmpxchg_u64_relaxed(ptr, old, new);

#endif

	}

	__cmpxchg_called_with_bad_pointer();

	return old;

}



static __always_inline unsigned long

__cmpxchg_acquire(void *ptr, unsigned long old, unsigned long new,

		  unsigned int size)

{

	switch (size) {

	case 4:

		return __cmpxchg_u32_acquire(ptr, old, new);

#ifdef CONFIG_PPC64

	case 8:

		return __cmpxchg_u64_acquire(ptr, old, new);

#endif

	}

	__cmpxchg_called_with_bad_pointer();

	return old;

}

#define cmpxchg(ptr, o, n)						 \

#define cmpxchg(ptr, o, n)						 \

  ({									 \

  ({									 \

     __typeof__(*(ptr)) _o_ = (o);					 \

     __typeof__(*(ptr)) _o_ = (o);					 \
@@ -279,6 +400,23 @@ __cmpxchg_local(volatile void *ptr, unsigned long old, unsigned long new, 
				    (unsigned long)_n_, sizeof(*(ptr))); \

				    (unsigned long)_n_, sizeof(*(ptr))); \

  })

  })





#define cmpxchg_relaxed(ptr, o, n)					\

({									\

	__typeof__(*(ptr)) _o_ = (o);					\

	__typeof__(*(ptr)) _n_ = (n);					\

	(__typeof__(*(ptr))) __cmpxchg_relaxed((ptr),			\

			(unsigned long)_o_, (unsigned long)_n_,		\

			sizeof(*(ptr)));				\

})



#define cmpxchg_acquire(ptr, o, n)					\

({									\

	__typeof__(*(ptr)) _o_ = (o);					\

	__typeof__(*(ptr)) _n_ = (n);					\

	(__typeof__(*(ptr))) __cmpxchg_acquire((ptr),			\

			(unsigned long)_o_, (unsigned long)_n_,		\

			sizeof(*(ptr)));				\

})

#ifdef CONFIG_PPC64

#ifdef CONFIG_PPC64

#define cmpxchg64(ptr, o, n)						\

#define cmpxchg64(ptr, o, n)						\

  ({									\

  ({									\
@@ -290,7 +428,16 @@ __cmpxchg_local(volatile void *ptr, unsigned long old, unsigned long new, 
	BUILD_BUG_ON(sizeof(*(ptr)) != 8);				\

	BUILD_BUG_ON(sizeof(*(ptr)) != 8);				\

	cmpxchg_local((ptr), (o), (n));					\

	cmpxchg_local((ptr), (o), (n));					\

  })

  })

#define cmpxchg64_relaxed	cmpxchg64_local

#define cmpxchg64_relaxed(ptr, o, n)					\

({									\

	BUILD_BUG_ON(sizeof(*(ptr)) != 8);				\

	cmpxchg_relaxed((ptr), (o), (n));				\

})

#define cmpxchg64_acquire(ptr, o, n)					\

({									\

	BUILD_BUG_ON(sizeof(*(ptr)) != 8);				\

	cmpxchg_acquire((ptr), (o), (n));				\

})

#else

#else

#include <asm-generic/cmpxchg-local.h>

#include <asm-generic/cmpxchg-local.h>

#define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n))

#define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n))