Messages in this thread | | | Date | Mon, 9 May 2016 15:28:51 +0800 | Subject | Re: [PATCH] workqueue: fix rebind bound workers warning | From | Wanpeng Li <> |
| |
Sorry to quick ping you Tejun, just hope it can catch the upcoming merge window. :-) 2016-05-05 9:41 GMT+08:00 Wanpeng Li <kernellwp@gmail.com>: > From: Wanpeng Li <wanpeng.li@hotmail.com> > > ------------[ cut here ]------------ > WARNING: CPU: 0 PID: 16 at kernel/workqueue.c:4559 rebind_workers+0x1c0/0x1d0 > Modules linked in: > CPU: 0 PID: 16 Comm: cpuhp/0 Not tainted 4.6.0-rc4+ #31 > Hardware name: IBM IBM System x3550 M4 Server -[7914IUW]-/00Y8603, BIOS -[D7E128FUS-1.40]- 07/23/2013 > 0000000000000000 ffff881037babb58 ffffffff8139d885 0000000000000010 > 0000000000000000 0000000000000000 0000000000000000 ffff881037babba8 > ffffffff8108505d ffff881037ba0000 000011cf3e7d6e60 0000000000000046 > Call Trace: > dump_stack+0x89/0xd4 > __warn+0xfd/0x120 > warn_slowpath_null+0x1d/0x20 > rebind_workers+0x1c0/0x1d0 > workqueue_cpu_up_callback+0xf5/0x1d0 > notifier_call_chain+0x64/0x90 > ? trace_hardirqs_on_caller+0xf2/0x220 > ? notify_prepare+0x80/0x80 > __raw_notifier_call_chain+0xe/0x10 > __cpu_notify+0x35/0x50 > notify_down_prepare+0x5e/0x80 > ? notify_prepare+0x80/0x80 > cpuhp_invoke_callback+0x73/0x330 > ? __schedule+0x33e/0x8a0 > cpuhp_down_callbacks+0x51/0xc0 > cpuhp_thread_fun+0xc1/0xf0 > smpboot_thread_fn+0x159/0x2a0 > ? smpboot_create_threads+0x80/0x80 > kthread+0xef/0x110 > ? wait_for_completion+0xf0/0x120 > ? schedule_tail+0x35/0xf0 > ret_from_fork+0x22/0x50 > ? __init_kthread_worker+0x70/0x70 > ---[ end trace eb12ae47d2382d8f ]--- > notify_down_prepare: attempt to take down CPU 0 failed > > This bug can be reproduced by below config w/ nohz_full= all cpus: > > CONFIG_BOOTPARAM_HOTPLUG_CPU0=y > CONFIG_DEBUG_HOTPLUG_CPU0=y > CONFIG_NO_HZ_FULL=y > > The boot CPU handles housekeeping duty(unbound timers, workqueues, > timekeeping, ...) on behalf of full dynticks CPUs. It must remain > online when nohz full is enabled. There is a priority set to every > notifier_blocks: > > workqueue_cpu_up > tick_nohz_cpu_down > workqueue_cpu_down > > So tick_nohz_cpu_down callback failed when down prepare cpu 0, and > notifier_blocks behind tick_nohz_cpu_down will not be called any > more, which leads to workers are actually not unbound. Then hotplug > state machine will fallback to undo and online cpu 0 again. Workers > will be rebound unconditionally even if they are not unbound and > trigger the warning in this progress. > > This patch fix it by catching !DISASSOCIATED to avoid rebind bound > workers. > > Cc: Tejun Heo <tj@kernel.org> > Cc: Lai Jiangshan <jiangshanlai@gmail.com> > Suggested-by: Lai Jiangshan <jiangshanlai@gmail.com> > Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com> > --- > kernel/workqueue.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/kernel/workqueue.c b/kernel/workqueue.c > index 2232ae3..cc18920 100644 > --- a/kernel/workqueue.c > +++ b/kernel/workqueue.c > @@ -4525,6 +4525,12 @@ static void rebind_workers(struct worker_pool *pool) > pool->attrs->cpumask) < 0); > > spin_lock_irq(&pool->lock); > + > + if (!(pool->flags & POOL_DISASSOCIATED)) { > + spin_unlock_irq(&pool->lock); > + return; > + } > + > pool->flags &= ~POOL_DISASSOCIATED; > > for_each_pool_worker(worker, pool) { > -- > 1.9.1 >
| |