On Thu, Aug 04, 2016 at 05:51:20PM +0800, Wanpeng Li wrote: > From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx> > > The dl task will be replenished after dl task timer fire and start a new > period. It will be enqueued and to re-evaluate its dependency on the tick > in order to restart it. However, if cpu is hot-unplug, irq_work_queue will > splash since the target cpu is offline. > > As a result: > > WARNING: CPU: 2 PID: 0 at kernel/irq_work.c:69 irq_work_queue_on+0xad/0xe0 > Call Trace: > dump_stack+0x99/0xd0 > __warn+0xd1/0xf0 > warn_slowpath_null+0x1d/0x20 > irq_work_queue_on+0xad/0xe0 > tick_nohz_full_kick_cpu+0x44/0x50 > tick_nohz_dep_set_cpu+0x74/0xb0 > enqueue_task_dl+0x226/0x480 > activate_task+0x5c/0xa0 > dl_task_timer+0x19b/0x2c0 > ? push_dl_task.part.31+0x190/0x190 Hurm, so this is after hot-unplug succeeded. We get a timer (which is also already migrated), but we enqueue the dl task on the offline CPU, because we need to do replenish because start_dl_timer() -- see the comment in dl_task_timer() at #ifdef CONFIG_SMP. Then, once we've enqueued the task on the offline cpu, do we migrate it. Bit icky that, but I don't immediately see a better way. And I think you're right in that we don't leak the nohz state, the migration, which we do immediately after this, takes care of that. Juri, any opinions? -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
