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/*
* File : atomic.c
* Author : Jérémy Zurcher <jeremy@asynk.ch>
* Date : 01/11/09
* License :
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*
*/
#include <stdio.h>
typedef struct split {
volatile void *ptr;
volatile unsigned int count;
} split_t;
typedef union pointer {
split_t split;
volatile unsigned long long concat;
} pointer_t;
/* CMPXCHG8B m64 Compare EDX:EAX with m64. If equal, set ZF and load ECX:EBX into m64. Else, clear ZF and load m64 into EDX:EAX. */
static inline unsigned int compare_and_swap(volatile unsigned long long *mem,
volatile unsigned long long old,
volatile unsigned long long new) {
char result;
__asm__ __volatile__("lock; cmpxchg8b %0; setz %1;"
: "=m"(*mem), "=q"(result)
: "m"(*mem), "d" ((unsigned long)(old>>32)), "a" ((unsigned long)old),
"c" ((unsigned long)(new>>32)), "b" ((unsigned long)new)
: "memory");
return (int)result;
}
/* CMPXCHG8B m64 Compare EDX:EAX with m64. If equal, set ZF and load ECX:EBX into m64. Else, clear ZF and load m64 into EDX:EAX. */
static inline unsigned int cas( volatile split_t *mem,
volatile split_t old,
volatile split_t new ) {
char result;
__asm__ __volatile__("lock; cmpxchg8b %0; setz %1;"
: "=m"(*mem), "=q"(result)
: "m"(*mem), "d" (old.count), "a" (old.ptr),
"c" (new.count), "b" (new.ptr)
: "memory");
return (int)result;
}
int test_compare_and_swap () {
pointer_t mem, old, new;
return compare_and_swap(&mem.concat, old.concat, new.concat);
}
int test_cas () {
pointer_t mem, old, new;
return cas(&mem.split, old.split, new.split);
}
int main( int argc, char*argv[], char*env[] ) {
int ret;
pointer_t mem, old, new;
mem.split.count = 0;
old.split.count = 6;
new.split.count = 666;
mem.split.ptr = (void*)&argc;
old.split.ptr = (void*)&argc;
new.split.ptr = (void*)&argv;
ret = compare_and_swap(&mem.concat, old.concat, new.concat);
printf("ret %d -> (%d,%X)\n", ret, mem.split.count, (unsigned int)mem.split.ptr);
mem.split.count=6;
ret = compare_and_swap(&mem.concat, old.concat, new.concat);
printf("ret %d -> (%d,%X)\n", ret, mem.split.count, (unsigned int)mem.split.ptr);
mem.split.count = 0;
old.split.count = 6;
new.split.count = 666;
mem.split.ptr = (void*)&argc;
old.split.ptr = (void*)&argc;
new.split.ptr = (void*)&argv;
ret = cas(&mem.split, old.split, new.split);
printf("ret %d -> (%d,%X)\n", ret, mem.split.count, (unsigned int)mem.split.ptr);
mem.split.count=6;
ret = cas(&mem.split, old.split, new.split);
printf("ret %d -> (%d,%X)\n", ret, mem.split.count, (unsigned int)mem.split.ptr);
return 0;
}
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