From 56c08e6d226c860ad097fa6ba109133228c56722 Mon Sep 17 00:00:00 2001 From: Boqun Feng Date: Tue, 15 Dec 2015 22:24:17 +0800 Subject: [PATCH] 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: Boqun Feng Signed-off-by: Michael Ellerman --- arch/powerpc/include/asm/atomic.h | 10 ++ arch/powerpc/include/asm/cmpxchg.h | 149 ++++++++++++++++++++++++++++- 2 files changed, 158 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/include/asm/atomic.h b/arch/powerpc/include/asm/atomic.h index a19fcdc318ee..ae0751ef8788 100644 --- a/arch/powerpc/include/asm/atomic.h +++ b/arch/powerpc/include/asm/atomic.h @@ -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_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_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_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_relaxed(v, new) xchg_relaxed(&((v)->counter), (new)) diff --git a/arch/powerpc/include/asm/cmpxchg.h b/arch/powerpc/include/asm/cmpxchg.h index 17c7e14b37ca..cae4fa85250c 100644 --- a/arch/powerpc/include/asm/cmpxchg.h +++ b/arch/powerpc/include/asm/cmpxchg.h @@ -181,6 +181,56 @@ __cmpxchg_u32_local(volatile unsigned int *p, unsigned long old, 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 static __always_inline unsigned long __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; } + +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 /* 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; } +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) \ ({ \ __typeof__(*(ptr)) _o_ = (o); \ @@ -279,6 +400,23 @@ __cmpxchg_local(volatile void *ptr, unsigned long old, unsigned long new, (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 #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); \ 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 #include #define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n)) -- 2.34.1