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158 lines
4.3 KiB
C
158 lines
4.3 KiB
C
#ifndef CAS_H
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#define CAS_H
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#include <stddef.h>
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/* Atomic operations for lock-free data structures.
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* We operate on machine words and use size_t as a type.
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* CAS stands for Compare And Swap, the most common operation. */
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/* The API was inspired by the Linux kernel */
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#if defined(__INTEL_COMPILER) || (__GNUC__ > 4) || ((__GNUC__ == 4) && (__GNUC_MINOR__ >= 1))
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#define USE_BUILTINS
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#endif
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/* if (*x == oldval) { *x=newval; return 1; } else return 0; */
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static inline int compare_and_swap(volatile size_t* x,size_t oldval,size_t newval) {
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#ifdef USE_BUILTINS
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return __sync_bool_compare_and_swap(x,oldval,newval);
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#elif defined(__i386__)
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char result;
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asm volatile ("lock; cmpxchgl %3, %0; setz %1" : "=m"(*x), "=q" (result) : "m" (*x), "r" (newval), "a" (oldval) : "memory");
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return result;
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#elif defined(__x86_64__)
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char result;
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asm volatile ("lock; cmpxchgq %3, %0; setz %1" : "=m"(*x), "=q" (result) : "m" (*x), "r" (newval), "a" (oldval) : "memory");
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return result;
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#else
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#error architecture not supported and gcc too old, edit CAS.h
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#endif
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}
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/* return *x += val; */
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static inline size_t atomic_add_return(size_t* x,size_t val) {
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#ifdef USE_BUILTINS
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return __sync_add_and_fetch(x,val);
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#elif defined(__i386__)
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size_t i = val;
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asm volatile ("lock; xaddl %1, %0" : "+m" (*x), "+r" (val) :: "memory" );
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return i + val;
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#elif defined(__x86_64__)
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size_t i = val;
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asm volatile ("lock; xaddq %1, %0" : "+m" (*x), "+r" (val) :: "memory" );
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return i + val;
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#else
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size_t y;
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for (y=*x; compare_and_swap(&x,y,y+val)==0; y=*x) ;
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return y+val;
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#endif
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}
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/* *x += val; */
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static inline void atomic_add(size_t* x,size_t val) {
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#ifdef USE_BUILTINS
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__sync_add_and_fetch(x,val);
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#elif defined(__i386__)
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asm volatile ("lock; addl %1, %0" : "+m" (*x) : "ir" (val) );
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#elif defined(__x86_64__)
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asm volatile ("lock; addq %1, %0" : "+m" (*x) : "ir" (val) );
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#else
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atomic_add_return(&x,val);
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#endif
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}
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static inline void atomic_inc(size_t* x) {
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#ifdef __i386__
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asm volatile ("lock; incl %0" : "+m" (*x) );
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#elif defined(__x86_64__)
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asm volatile ("lock; incq %0" : "+m" (*x) );
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#else
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atomic_add(x,1);
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#endif
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}
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static inline size_t atomic_inc_return(size_t* x) {
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return atomic_add_return(x,1);
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}
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static inline void atomic_dec(size_t* x) {
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#ifdef __i386__
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asm volatile ("lock; decl %0" : "+m" (*x) );
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#elif defined(__x86_64__)
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asm volatile ("lock; decq %0" : "+m" (*x) );
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#else
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atomic_add(x,-1);
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#endif
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}
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static inline size_t atomic_dec_return(size_t* x) {
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return atomic_add_return(x,-1);
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}
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/* *x |= val; */
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static inline void atomic_or(volatile size_t* x,size_t val) {
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#ifdef USE_BUILTINS
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__sync_or_and_fetch(x,val);
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#elif defined(__i386__)
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asm volatile ("lock; orl %1, %0" : "+m" (*x) : "r" (val) );
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#elif defined(__x86_64__)
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asm volatile ("lock; orq %1, %0" : "+m" (*x) : "r" (val) );
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#else
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#error architecture not supported and gcc too old, edit CAS.h
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#endif
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}
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/* *x &= val; */
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static inline void atomic_and(volatile size_t* x,size_t val) {
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#ifdef USE_BUILTINS
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__sync_and_and_fetch(x,val);
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#elif defined(__i386__)
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asm volatile ("lock; andl %1, %0" : "+m" (*x) : "r" (val) );
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#elif defined(__x86_64__)
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asm volatile ("lock; andq %1, %0" : "+m" (*x) : "r" (val) );
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#else
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#error architecture not supported and gcc too old, edit CAS.h
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#endif
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}
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/* Optimization barrier */
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/* The "volatile" is due to gcc bugs */
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#define barrier() __asm__ __volatile__("": : :"memory")
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#if defined(__i386__) || defined(__x86_64__)
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#define mb() asm volatile("mfence":::"memory")
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#define rmb() asm volatile("lfence":::"memory")
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#define wmb() asm volatile("sfence":::"memory")
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/* Atomic operations are already serializing on x86 */
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#define smp_mb__before_atomic_dec() barrier()
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#define smp_mb__after_atomic_dec() barrier()
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#define smp_mb__before_atomic_inc() barrier()
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#define smp_mb__after_atomic_inc() barrier()
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#elif defined(__powerpc__)
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#define mb() asm volatile("sync":::"memory")
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#define rmb() asm volatile("sync":::"memory")
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#define wmb() asm volatile("sync":::"memory")
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#define smp_mb__before_atomic_dec() mb()
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#define smp_mb__after_atomic_dec() mb()
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#define smp_mb__before_atomic_inc() mb()
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#define smp_mb__after_atomic_inc() mb()
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#elif defined(USE_BUILTINS)
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#define mb() __sync_synchronize()
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#define rmb() __sync_synchronize()
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#define wmb() __sync_synchronize()
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#endif
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#undef USE_BUILTINS
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#endif
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