On 06/10, Gaurav Kohli wrote: > > >@@ -1991,6 +1991,28 @@ try_to_wake_up(struct task_struct *p, un > > unsigned long flags; > > int cpu, success = 0; > >+ if (p == current) { > >+ /* > >+ * We're waking current, this means 'p->on_rq' and 'task_cpu(p) > >+ * == smp_processor_id()'. Together this means we can special > >+ * case the whole 'p->on_rq && ttwu_remote()' case below > >+ * without taking any locks. > >+ * > >+ * In particular: > >+ * - we rely on Program-Order guarantees for all the ordering, > >+ * - we're serialized against set_special_state() by virtue of > >+ * it disabling IRQs (this allows not taking ->pi_lock). > >+ */ > >+ if (!(p->state & state)) > >+ return false; > >+ > > Hi Peter, Jen, > > As we are not taking pi_lock here , is there possibility of same task dead > call comes as this point of time for current thread, bcoz of which we have > seen earlier issue after this commit 0619317ff8ba > [T114538] do_task_dead+0xf0/0xf8 > [T114538] do_exit+0xd5c/0x10fc > [T114538] do_group_exit+0xf4/0x110 > [T114538] get_signal+0x280/0xdd8 > [T114538] do_notify_resume+0x720/0x968 > [T114538] work_pending+0x8/0x10 > > Is there a chance of TASK_DEAD set at this point of time? In this case try_to_wake_up(current, TASK_NORMAL) will do nothing, see the if (!(p->state & state)) above. See also the comment about set_special_state() above. It disables irqs and this is enough to ensure that try_to_wake_up(current) from irq can't race with set_special_state(TASK_DEAD). Oleg.