/*
* Unlike a traditional lock-less linked list; the availability of a
* rseq primitive allows us to implement pop without concerns over
* ABA-type races.
*/
struct percpu_list_node *this_cpu_list_pop(struct percpu_list *list,
int *_cpu)
{
for (;;) {
struct percpu_list_node *head;
intptr_t *targetptr, expectnot, *load;
off_t offset;
int ret, cpu;
cpu = rseq_cpu_start();
targetptr = (intptr_t *)&list->c[cpu].head;
expectnot = (intptr_t)NULL;
offset = offsetof(struct percpu_list_node, next);
load = (intptr_t *)&head;
ret = rseq_cmpnev_storeoffp_load(targetptr, expectnot,
offset, load, cpu);
if (rseq_likely(!ret)) {
if (_cpu)
*_cpu = cpu;
return head;
}
if (ret > 0)
return NULL;
/* Retry if rseq aborts. */
}
}
/* A simple percpu spinlock. Returns the cpu lock was acquired on. */
int rseq_this_cpu_lock(struct percpu_lock *lock)
{
int cpu;
for (;;) {
int ret;
cpu = rseq_cpu_start();
ret = rseq_cmpeqv_storev(&lock->c[cpu].v,
0, 1, cpu);
if (rseq_likely(!ret))
break;
/* Retry if comparison fails or rseq aborts. */
}
/*
* Acquire semantic when taking lock after control dependency.
* Matches rseq_smp_store_release().
*/
rseq_smp_acquire__after_ctrl_dep();
return cpu;
}
void this_cpu_list_push(struct percpu_list *list,
struct percpu_list_node *node,
int *_cpu)
{
int cpu;
for (;;) {
intptr_t *targetptr, newval, expect;
int ret;
cpu = rseq_cpu_start();
/* Load list->c[cpu].head with single-copy atomicity. */
expect = (intptr_t)RSEQ_READ_ONCE(list->c[cpu].head);
newval = (intptr_t)node;
targetptr = (intptr_t *)&list->c[cpu].head;
node->next = (struct percpu_list_node *)expect;
ret = rseq_cmpeqv_storev(targetptr, expect, newval, cpu);
if (rseq_likely(!ret))
break;
/* Retry if comparison fails or rseq aborts. */
}
if (_cpu)
*_cpu = cpu;
}
int main(int argc, char **argv)
{
int cpu, ret;
if (rseq_register_current_thread())
abort();
cpu = rseq_cpu_start();
ret = rseq_addv(&v, 1, cpu);
if (ret)
goto end;
ret = rseq_addv(&v, 1, cpu);
if (ret)
goto end;
ret = rseq_addv(&v, 1, cpu);
if (ret)
goto end;
ret = rseq_addv(&v, 1, cpu);
if (ret)
goto end;
ret = rseq_addv(&v, 1, cpu);
if (ret)
goto end;
ret = rseq_addv(&v, 1, cpu);
if (ret)
goto end;
ret = rseq_addv(&v, 1, cpu);
if (ret)
goto end;
ret = rseq_addv(&v, 1, cpu);
if (ret)
goto end;
ret = rseq_addv(&v, 1, cpu);
if (ret)
goto end;
ret = rseq_addv(&v, 1, cpu);
if (ret)
goto end;
ret = rseq_addv(&v, 1, cpu);
if (ret)
goto end;
ret = rseq_addv(&v, 1, cpu);
if (ret)
goto end;
ret = rseq_addv(&v, 1, cpu);
if (ret)
goto end;
ret = rseq_addv(&v, 1, cpu);
if (ret)
goto end;
ret = rseq_addv(&v, 1, cpu);
if (ret)
goto end;
ret = rseq_addv(&v, 1, cpu);
if (ret)
goto end;
ret = rseq_addv(&v, 1, cpu);
if (ret)
goto end;
ret = rseq_addv(&v, 1, cpu);
if (ret)
goto end;
ret = rseq_addv(&v, 1, cpu);
if (ret)
goto end;
ret = rseq_addv(&v, 1, cpu);
if (ret)
goto end;
ret = rseq_addv(&v, 1, cpu);
if (ret)
goto end;
ret = rseq_addv(&v, 1, cpu);
if (ret)
goto end;
ret = rseq_addv(&v, 1, cpu);
if (ret)
goto end;
ret = rseq_addv(&v, 1, cpu);
if (ret)
goto end;
ret = rseq_addv(&v, 1, cpu);
if (ret)
goto end;
ret = rseq_addv(&v, 1, cpu);
if (ret)
goto end;
ret = rseq_addv(&v, 1, cpu);
if (ret)
goto end;
ret = rseq_addv(&v, 1, cpu);
if (ret)
goto end;
end:
if (rseq_unregister_current_thread())
abort();
printf("total %" PRIdPTR "\n", v);
return 0;
}
