Introduce an atomic_cmpxchg operation. Signed-off-by: Nick Piggin Index: linux-2.6/include/asm-i386/atomic.h =================================================================== --- linux-2.6.orig/include/asm-i386/atomic.h +++ linux-2.6/include/asm-i386/atomic.h @@ -215,6 +215,8 @@ static __inline__ int atomic_sub_return( return atomic_add_return(-i,v); } +#define atomic_cmpxchg(v, old, new) ((int)cmpxchg(&((v)->counter), old, new)) + #define atomic_inc_return(v) (atomic_add_return(1,v)) #define atomic_dec_return(v) (atomic_sub_return(1,v)) Index: linux-2.6/include/asm-ppc64/atomic.h =================================================================== --- linux-2.6.orig/include/asm-ppc64/atomic.h +++ linux-2.6/include/asm-ppc64/atomic.h @@ -162,6 +162,8 @@ static __inline__ int atomic_dec_return( return t; } +#define atomic_cmpxchg(v, o, n) ((int)cmpxchg(&((v)->counter), (o), (n))) + #define atomic_sub_and_test(a, v) (atomic_sub_return((a), (v)) == 0) #define atomic_dec_and_test(v) (atomic_dec_return((v)) == 0) Index: linux-2.6/include/asm-ia64/atomic.h =================================================================== --- linux-2.6.orig/include/asm-ia64/atomic.h +++ linux-2.6/include/asm-ia64/atomic.h @@ -88,6 +88,8 @@ ia64_atomic64_sub (__s64 i, atomic64_t * return new; } +#define atomic_cmpxchg(v, old, new) ((int)cmpxchg(&((v)->counter), old, new)) + #define atomic_add_return(i,v) \ ({ \ int __ia64_aar_i = (i); \ Index: linux-2.6/include/asm-x86_64/atomic.h =================================================================== --- linux-2.6.orig/include/asm-x86_64/atomic.h +++ linux-2.6/include/asm-x86_64/atomic.h @@ -360,6 +360,8 @@ static __inline__ int atomic_sub_return( return atomic_add_return(-i,v); } +#define atomic_cmpxchg(v, old, new) ((int)cmpxchg(&((v)->counter), old, new)) + #define atomic_inc_return(v) (atomic_add_return(1,v)) #define atomic_dec_return(v) (atomic_sub_return(1,v)) Index: linux-2.6/Documentation/atomic_ops.txt =================================================================== --- linux-2.6.orig/Documentation/atomic_ops.txt +++ linux-2.6/Documentation/atomic_ops.txt @@ -115,6 +115,21 @@ boolean is return which indicates whethe is negative. It requires explicit memory barrier semantics around the operation. +Finally: + + int atomic_cmpxchg(atomic_t *v, int old, int new); + +This performs an atomic compare exchange operation on the atomic value v, +with the given old and new values. Like all atomic_xxx operations, +atomic_cmpxchg will only satisfy its atomicity semantics as long as all +other accesses of *v are performed through atomic_xxx operations. + +atomic_cmpxchg requires explicit memory barriers around the operation. + +The semantics for atomic_cmpxchg are the same as those defined for 'cas' +below. + + If a caller requires memory barrier semantics around an atomic_t operation which does not return a value, a set of interfaces are defined which accomplish this: Index: linux-2.6/arch/sparc/lib/atomic32.c =================================================================== --- linux-2.6.orig/arch/sparc/lib/atomic32.c +++ linux-2.6/arch/sparc/lib/atomic32.c @@ -38,6 +38,20 @@ int __atomic_add_return(int i, atomic_t return ret; } +int atomic_cmpxchg(atomic_t *v, int old, int new) +{ + int ret; + unsigned long flags; + spin_lock_irqsave(ATOMIC_HASH(v), flags); + + ret = v->counter; + if (likely(ret == old)) + v->counter = new; + + spin_unlock_irqrestore(ATOMIC_HASH(v), flags); + return ret; +} + void atomic_set(atomic_t *v, int i) { unsigned long flags; Index: linux-2.6/include/asm-sparc/atomic.h =================================================================== --- linux-2.6.orig/include/asm-sparc/atomic.h +++ linux-2.6/include/asm-sparc/atomic.h @@ -19,6 +19,7 @@ typedef struct { volatile int counter; } #define ATOMIC_INIT(i) { (i) } extern int __atomic_add_return(int, atomic_t *); +extern int atomic_cmpxchg(atomic_t *, int, int); extern void atomic_set(atomic_t *, int); #define atomic_read(v) ((v)->counter) Index: linux-2.6/include/asm-alpha/atomic.h =================================================================== --- linux-2.6.orig/include/asm-alpha/atomic.h +++ linux-2.6/include/asm-alpha/atomic.h @@ -171,6 +171,8 @@ static __inline__ long atomic64_sub_retu return result; } +#define atomic_cmpxchg(v, o, n) ((int)cmpxchg(&((v)->counter), (o), (n))) + #define atomic_dec_return(v) atomic_sub_return(1,(v)) #define atomic64_dec_return(v) atomic64_sub_return(1,(v)) Index: linux-2.6/include/asm-m68k/atomic.h =================================================================== --- linux-2.6.orig/include/asm-m68k/atomic.h +++ linux-2.6/include/asm-m68k/atomic.h @@ -139,6 +139,8 @@ static inline void atomic_set_mask(unsig __asm__ __volatile__("orl %1,%0" : "+m" (*v) : "id" (mask)); } +#define atomic_cmpxchg(v, o, n) ((int)cmpxchg(&((v)->counter), (o), (n))) + /* Atomic operations are already serializing */ #define smp_mb__before_atomic_dec() barrier() #define smp_mb__after_atomic_dec() barrier() Index: linux-2.6/include/asm-m68knommu/atomic.h =================================================================== --- linux-2.6.orig/include/asm-m68knommu/atomic.h +++ linux-2.6/include/asm-m68knommu/atomic.h @@ -128,6 +128,8 @@ extern __inline__ int atomic_sub_return( return temp; } +#define atomic_cmpxchg(v, o, n) ((int)cmpxchg(&((v)->counter), (o), (n))) + #define atomic_dec_return(v) atomic_sub_return(1,(v)) #define atomic_inc_return(v) atomic_add_return(1,(v)) Index: linux-2.6/include/asm-mips/atomic.h =================================================================== --- linux-2.6.orig/include/asm-mips/atomic.h +++ linux-2.6/include/asm-mips/atomic.h @@ -267,6 +267,8 @@ static __inline__ int atomic_sub_if_posi return result; } +#define atomic_cmpxchg(v, o, n) ((int)cmpxchg(&((v)->counter), (o), (n))) + #define atomic_dec_return(v) atomic_sub_return(1,(v)) #define atomic_inc_return(v) atomic_add_return(1,(v)) Index: linux-2.6/include/asm-parisc/atomic.h =================================================================== --- linux-2.6.orig/include/asm-parisc/atomic.h +++ linux-2.6/include/asm-parisc/atomic.h @@ -164,6 +164,7 @@ static __inline__ int atomic_read(const } /* exported interface */ +#define atomic_cmpxchg(v, o, n) ((int)cmpxchg(&((v)->counter), (o), (n))) #define atomic_add(i,v) ((void)(__atomic_add_return( ((int)i),(v)))) #define atomic_sub(i,v) ((void)(__atomic_add_return(-((int)i),(v)))) Index: linux-2.6/include/asm-ppc/atomic.h =================================================================== --- linux-2.6.orig/include/asm-ppc/atomic.h +++ linux-2.6/include/asm-ppc/atomic.h @@ -177,6 +177,8 @@ static __inline__ int atomic_dec_return( return t; } +#define atomic_cmpxchg(v, o, n) ((int)cmpxchg(&((v)->counter), (o), (n))) + #define atomic_sub_and_test(a, v) (atomic_sub_return((a), (v)) == 0) #define atomic_dec_and_test(v) (atomic_dec_return((v)) == 0) Index: linux-2.6/include/asm-s390/atomic.h =================================================================== --- linux-2.6.orig/include/asm-s390/atomic.h +++ linux-2.6/include/asm-s390/atomic.h @@ -198,6 +198,8 @@ atomic_compare_and_swap(int expected_old return retval; } +#define atomic_cmpxchg(v, o, n) (atomic_compare_and_swap((o), (n), &((v)->counter))) + #define smp_mb__before_atomic_dec() smp_mb() #define smp_mb__after_atomic_dec() smp_mb() #define smp_mb__before_atomic_inc() smp_mb() Index: linux-2.6/include/asm-sparc64/atomic.h =================================================================== --- linux-2.6.orig/include/asm-sparc64/atomic.h +++ linux-2.6/include/asm-sparc64/atomic.h @@ -70,6 +70,8 @@ extern int atomic64_sub_ret(int, atomic6 #define atomic_add_negative(i, v) (atomic_add_ret(i, v) < 0) #define atomic64_add_negative(i, v) (atomic64_add_ret(i, v) < 0) +#define atomic_cmpxchg(v, o, n) ((int)cmpxchg(&((v)->counter), (o), (n))) + /* Atomic operations are already serializing */ #ifdef CONFIG_SMP #define smp_mb__before_atomic_dec() membar_storeload_loadload(); Index: linux-2.6/include/asm-arm26/atomic.h =================================================================== --- linux-2.6.orig/include/asm-arm26/atomic.h +++ linux-2.6/include/asm-arm26/atomic.h @@ -62,6 +62,20 @@ static inline int atomic_sub_return(int return val; } +static inline int atomic_cmpxchg(atomic_t *v, int old, int new) +{ + int ret; + unsigned long flags; + + local_irq_save(flags); + ret = v->counter; + if (likely(ret == old)) + v->counter = new; + local_irq_restore(flags); + + return ret; +} + static inline void atomic_clear_mask(unsigned long mask, unsigned long *addr) { unsigned long flags; Index: linux-2.6/include/asm-frv/atomic.h =================================================================== --- linux-2.6.orig/include/asm-frv/atomic.h +++ linux-2.6/include/asm-frv/atomic.h @@ -414,4 +414,6 @@ extern uint32_t __cmpxchg_32(uint32_t *v #endif +#define atomic_cmpxchg(v, old, new) ((int)cmpxchg(&((v)->counter), old, new)) + #endif /* _ASM_ATOMIC_H */ Index: linux-2.6/include/asm-h8300/atomic.h =================================================================== --- linux-2.6.orig/include/asm-h8300/atomic.h +++ linux-2.6/include/asm-h8300/atomic.h @@ -82,6 +82,18 @@ static __inline__ int atomic_dec_and_tes return ret == 0; } +static __inline__ int atomic_cmpxchg(atomic_t *v, int old, int new) +{ + int ret; + unsigned long flags; + local_irq_save(flags); + ret = v->counter; + if (likely(ret == old)) + v->counter = new; + local_irq_restore(flags); + return ret; +} + static __inline__ void atomic_clear_mask(unsigned long mask, unsigned long *v) { __asm__ __volatile__("stc ccr,r1l\n\t" Index: linux-2.6/include/asm-sh64/atomic.h =================================================================== --- linux-2.6.orig/include/asm-sh64/atomic.h +++ linux-2.6/include/asm-sh64/atomic.h @@ -99,6 +99,20 @@ static __inline__ int atomic_sub_return( #define atomic_inc(v) atomic_add(1,(v)) #define atomic_dec(v) atomic_sub(1,(v)) +static __inline__ int atomic_cmpxchg(atomic_t *v, int old, int new) +{ + int ret; + unsigned long flags; + + local_irq_save(flags); + ret = v->counter; + if (likely(ret == old)) + v->counter = new; + local_irq_restore(flags); + + return ret; +} + static __inline__ void atomic_clear_mask(unsigned int mask, atomic_t *v) { unsigned long flags; Index: linux-2.6/include/asm-v850/atomic.h =================================================================== --- linux-2.6.orig/include/asm-v850/atomic.h +++ linux-2.6/include/asm-v850/atomic.h @@ -90,6 +90,20 @@ static __inline__ void atomic_clear_mask #define atomic_dec_and_test(v) (atomic_sub_return (1, (v)) == 0) #define atomic_add_negative(i,v) (atomic_add_return ((i), (v)) < 0) +static __inline__ int atomic_cmpxchg(atomic_t *v, int old, int new) +{ + int ret; + unsigned long flags; + + local_irq_save(flags); + ret = v->counter; + if (likely(ret == old)) + v->counter = new; + local_irq_restore(flags); + + return ret; +} + /* Atomic operations are already serializing on ARM */ #define smp_mb__before_atomic_dec() barrier() #define smp_mb__after_atomic_dec() barrier() Index: linux-2.6/include/asm-xtensa/atomic.h =================================================================== --- linux-2.6.orig/include/asm-xtensa/atomic.h +++ linux-2.6/include/asm-xtensa/atomic.h @@ -223,6 +223,7 @@ static inline int atomic_sub_return(int */ #define atomic_add_negative(i,v) (atomic_add_return((i),(v)) < 0) +#define atomic_cmpxchg(v, o, n) ((int)cmpxchg(&((v)->counter), (o), (n))) static inline void atomic_clear_mask(unsigned int mask, atomic_t *v) { Index: linux-2.6/include/asm-sh/atomic.h =================================================================== --- linux-2.6.orig/include/asm-sh/atomic.h +++ linux-2.6/include/asm-sh/atomic.h @@ -87,6 +87,20 @@ static __inline__ int atomic_sub_return( #define atomic_inc(v) atomic_add(1,(v)) #define atomic_dec(v) atomic_sub(1,(v)) +static __inline__ int atomic_cmpxchg(atomic_t *v, int old, int new) +{ + int ret; + unsigned long flags; + + local_irq_save(flags); + ret = v->counter; + if (likely(ret == old)) + v->counter = new; + local_irq_restore(flags); + + return ret; +} + static __inline__ void atomic_clear_mask(unsigned int mask, atomic_t *v) { unsigned long flags; Index: linux-2.6/include/asm-arm/atomic.h =================================================================== --- linux-2.6.orig/include/asm-arm/atomic.h +++ linux-2.6/include/asm-arm/atomic.h @@ -80,6 +80,23 @@ static inline int atomic_sub_return(int return result; } +static inline int atomic_cmpxchg(atomic_t *ptr, int old, int new) +{ + u32 oldval, res; + + do { + __asm__ __volatile__("@ atomic_cmpxchg\n" + "ldrex %1, [%2]\n" + "teq %1, %3\n" + "strexeq %0, %4, [%2]\n" + : "=&r" (res), "=&r" (oldval) + : "r" (&ptr->counter), "r" (old), "r" (new) + : "cc"); + } while (res); + + return oldval; +} + static inline void atomic_clear_mask(unsigned long mask, unsigned long *addr) { unsigned long tmp, tmp2; @@ -131,6 +148,21 @@ static inline int atomic_sub_return(int return val; } +static inline int atomic_cmpxchg(atomic_t *v, int old, int new) +{ + int ret; + unsigned long flags; + + local_irq_save(flags); + ret = v->counter; + if (likely(ret == old)) + v->counter = new; + local_irq_restore(flags); + + return ret; +} + +static inline void atomic_clear_mask(unsigned long mask, unsigned long *addr) static inline void atomic_clear_mask(unsigned long mask, unsigned long *addr) { unsigned long flags; Index: linux-2.6/include/asm-cris/atomic.h =================================================================== --- linux-2.6.orig/include/asm-cris/atomic.h +++ linux-2.6/include/asm-cris/atomic.h @@ -123,6 +123,19 @@ extern __inline__ int atomic_inc_and_tes return retval; } +static __inline__ int atomic_cmpxchg(atomic_t *v, int old, int new) +{ + int ret; + unsigned long flags; + cris_atomic_save(v, flags); + ret = v->counter; + if (likely(ret == old)) + v->counter = new; + cris_atomic_restore(v, flags); + return ret; +} + +static inline void atomic_clear_mask(unsigned long mask, unsigned long *addr) /* Atomic operations are already serializing */ #define smp_mb__before_atomic_dec() barrier() #define smp_mb__after_atomic_dec() barrier()