On Mon, May 25, 2020 at 03:21:05PM +0200, Peter Zijlstra wrote:
> @@ -2320,7 +2304,7 @@ static void ttwu_queue_remote(struct task_struct *p,
> int cpu, int wake_flags)
>
> if (llist_add(&p->wake_entry, &rq->wake_list)) {
> if (!set_nr_if_polling(rq->idle))
> - smp_call_function_single_async(cpu, &rq->wake_csd);
> + smp_call_function_single_async(cpu, &p->wake_csd);
> else
> trace_sched_wake_idle_without_ipi(cpu);
Ok that's of course very unlikely but could it be possible to have the
following:
CPU 0 CPU 1 CPU 2
-----
//Wake up A
ttwu_queue(TASK A, CPU 1) idle_loop {
ttwu_queue_pending {
....
raw_spin_unlock_irqrestore(rq)
# VMEXIT (with IPI still pending)
//task
A migrates here
wait_event(....)
//sleep
//Wake up A
ttwu_queue(TASK A, CPU 2) {
//IPI on CPU 2 ignored
// due to csd->flags == CSD_LOCK
