On Tue, 2010-06-22 at 21:52 +0800, Wu Fengguang wrote:
> #include <stdio.h>
>
> typedef struct {
> int counter;
> } atomic_t;
>
> static inline int atomic_dec_and_test(atomic_t *v)
> {
> unsigned char c;
>
> asm volatile("lock; decl %0; sete %1"
> : "+m" (v->counter), "=qm" (c)
> : : "memory");
> return c != 0;
> }
>
> int main(void)
> {
> atomic_t i;
>
> i.counter = 100000000;
>
> for (; !atomic_dec_and_test(&i);)
> ;
>
> return 0;
> }
This test utterly fails to stress the concurrency, you want to create
nr_cpus threads and then pound the global variable. Then compare it
against the per-cpu-counter variant.
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