On Mon, May 25, 2020 at 04:05:49PM +0200, Frederic Weisbecker wrote: > 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 >
Right you are. Bah! More thinking....