Re: localed stuck in recent 3.18 git in copy_net_ns?

From: Paul E. McKenney
Date: Fri Oct 24 2014 - 19:03:26 EST

On Fri, Oct 24, 2014 at 03:34:07PM -0700, Jay Vosburgh wrote:
> Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> wrote:
>
> >On Sat, Oct 25, 2014 at 12:25:57AM +0300, Yanko Kaneti wrote:
> >> On Fri-10/24/14-2014 11:32, Paul E. McKenney wrote:
> >> > On Fri, Oct 24, 2014 at 08:35:26PM +0300, Yanko Kaneti wrote:
> >> > > On Fri-10/24/14-2014 10:20, Paul E. McKenney wrote:
> >
> >[ . . . ]
> >
> >> > > > Well, if you are feeling aggressive, give the following patch a spin.
> >> > > > I am doing sanity tests on it in the meantime.
> >> > >
> >> > > Doesn't seem to make a difference here
> >> >
> >> > OK, inspection isn't cutting it, so time for tracing. Does the system
> >> > respond to user input? If so, please enable rcu:rcu_barrier ftrace before
> >> > the problem occurs, then dump the trace buffer after the problem occurs.
> >>
> >> Sorry for being unresposive here, but I know next to nothing about tracing
> >> or most things about the kernel, so I have some cathing up to do.
> >>
> >> In the meantime some layman observations while I tried to find what exactly
> >> triggers the problem.
> >> - Even in runlevel 1 I can reliably trigger the problem by starting libvirtd
> >> - libvirtd seems to be very active in using all sorts of kernel facilities
> >> that are modules on fedora so it seems to cause many simultaneous kworker
> >> calls to modprobe
> >> - there are 8 kworker/u16 from 0 to 7
> >> - one of these kworkers always deadlocks, while there appear to be two
> >> kworker/u16:6 - the seventh
> >
> >Adding Tejun on CC in case this duplication of kworker/u16:6 is important.
> >
> >> 6 vs 8 as in 6 rcuos where before they were always 8
> >>
> >> Just observations from someone who still doesn't know what the u16
> >> kworkers are..
> >
> >Could you please run the following diagnostic patch? This will help
> >me see if I have managed to miswire the rcuo kthreads. It should
> >print some information at task-hang time.
>
> Here's the output of the patch; I let it sit through two hang
> cycles.
>
> -J
>
>
> [ 240.348020] INFO: task ovs-vswitchd:902 blocked for more than 120 seconds.
> [ 240.354878] Not tainted 3.17.0-testola+ #4
> [ 240.359481] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [ 240.367285] ovs-vswitchd D ffff88013fc94600 0 902 901 0x00000004
> [ 240.367290] ffff8800ab20f7b8 0000000000000002 ffff8800b3304b00 ffff8800ab20ffd8
> [ 240.367293] 0000000000014600 0000000000014600 ffff8800b0810000 ffff8800b3304b00
> [ 240.367296] ffff8800b3304b00 ffffffff81c59850 ffffffff81c59858 7fffffffffffffff
> [ 240.367300] Call Trace:
> [ 240.367307] [<ffffffff81722b99>] schedule+0x29/0x70
> [ 240.367310] [<ffffffff81725b6c>] schedule_timeout+0x1dc/0x260
> [ 240.367313] [<ffffffff81722f69>] ? _cond_resched+0x29/0x40
> [ 240.367316] [<ffffffff81723818>] ? wait_for_completion+0x28/0x160
> [ 240.367321] [<ffffffff811081a7>] ? queue_stop_cpus_work+0xc7/0xe0
> [ 240.367324] [<ffffffff81723896>] wait_for_completion+0xa6/0x160
> [ 240.367328] [<ffffffff81099980>] ? wake_up_state+0x20/0x20
> [ 240.367331] [<ffffffff810d0ecc>] _rcu_barrier+0x20c/0x480
> [ 240.367334] [<ffffffff810d1195>] rcu_barrier+0x15/0x20
> [ 240.367338] [<ffffffff81625010>] netdev_run_todo+0x60/0x300
> [ 240.367341] [<ffffffff8162f9ee>] rtnl_unlock+0xe/0x10
> [ 240.367349] [<ffffffffa01ffcc5>] internal_dev_destroy+0x55/0x80 [openvswitch]
> [ 240.367354] [<ffffffffa01ff622>] ovs_vport_del+0x32/0x40 [openvswitch]
> [ 240.367358] [<ffffffffa01f8dd0>] ovs_dp_detach_port+0x30/0x40 [openvswitch]
> [ 240.367363] [<ffffffffa01f8ea5>] ovs_vport_cmd_del+0xc5/0x110 [openvswitch]
> [ 240.367367] [<ffffffff81651d75>] genl_family_rcv_msg+0x1a5/0x3c0
> [ 240.367370] [<ffffffff81651f90>] ? genl_family_rcv_msg+0x3c0/0x3c0
> [ 240.367372] [<ffffffff81652021>] genl_rcv_msg+0x91/0xd0
> [ 240.367376] [<ffffffff81650091>] netlink_rcv_skb+0xc1/0xe0
> [ 240.367378] [<ffffffff816505bc>] genl_rcv+0x2c/0x40
> [ 240.367381] [<ffffffff8164f626>] netlink_unicast+0xf6/0x200
> [ 240.367383] [<ffffffff8164fa4d>] netlink_sendmsg+0x31d/0x780
> [ 240.367387] [<ffffffff8164ca74>] ? netlink_rcv_wake+0x44/0x60
> [ 240.367391] [<ffffffff81606a53>] sock_sendmsg+0x93/0xd0
> [ 240.367395] [<ffffffff81337700>] ? apparmor_capable+0x60/0x60
> [ 240.367399] [<ffffffff81614f27>] ? verify_iovec+0x47/0xd0
> [ 240.367402] [<ffffffff81606e79>] ___sys_sendmsg+0x399/0x3b0
> [ 240.367406] [<ffffffff812598a2>] ? kernfs_seq_stop_active+0x32/0x40
> [ 240.367410] [<ffffffff8101c385>] ? native_sched_clock+0x35/0x90
> [ 240.367413] [<ffffffff8101c385>] ? native_sched_clock+0x35/0x90
> [ 240.367416] [<ffffffff8101c3e9>] ? sched_clock+0x9/0x10
> [ 240.367420] [<ffffffff811277fc>] ? acct_account_cputime+0x1c/0x20
> [ 240.367424] [<ffffffff8109ce6b>] ? account_user_time+0x8b/0xa0
> [ 240.367428] [<ffffffff81200bd5>] ? __fget_light+0x25/0x70
> [ 240.367431] [<ffffffff81607c02>] __sys_sendmsg+0x42/0x80
> [ 240.367433] [<ffffffff81607c52>] SyS_sendmsg+0x12/0x20
> [ 240.367436] [<ffffffff81727464>] tracesys_phase2+0xd8/0xdd
> [ 240.367439] rcu_show_nocb_setup(): rcu_sched nocb state:
> [ 240.372734] 0: ffff88013fc0e600 l:ffff88013fc0e600 n:ffff88013fc8e600 .G.
> [ 240.379673] 1: ffff88013fc8e600 l:ffff88013fc0e600 n: (null) .G.
> [ 240.386611] 2: ffff88013fd0e600 l:ffff88013fd0e600 n:ffff88013fd8e600 N..
> [ 240.393550] 3: ffff88013fd8e600 l:ffff88013fd0e600 n: (null) N..
> [ 240.400489] rcu_show_nocb_setup(): rcu_bh nocb state:
> [ 240.405525] 0: ffff88013fc0e3c0 l:ffff88013fc0e3c0 n:ffff88013fc8e3c0 ...
> [ 240.412463] 1: ffff88013fc8e3c0 l:ffff88013fc0e3c0 n: (null) ...
> [ 240.419401] 2: ffff88013fd0e3c0 l:ffff88013fd0e3c0 n:ffff88013fd8e3c0 ...
> [ 240.426339] 3: ffff88013fd8e3c0 l:ffff88013fd0e3c0 n: (null) ...
> [ 360.432020] INFO: task ovs-vswitchd:902 blocked for more than 120 seconds.
> [ 360.438881] Not tainted 3.17.0-testola+ #4
> [ 360.443484] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [ 360.451289] ovs-vswitchd D ffff88013fc94600 0 902 901 0x00000004
> [ 360.451293] ffff8800ab20f7b8 0000000000000002 ffff8800b3304b00 ffff8800ab20ffd8
> [ 360.451297] 0000000000014600 0000000000014600 ffff8800b0810000 ffff8800b3304b00
> [ 360.451300] ffff8800b3304b00 ffffffff81c59850 ffffffff81c59858 7fffffffffffffff
> [ 360.451303] Call Trace:
> [ 360.451311] [<ffffffff81722b99>] schedule+0x29/0x70
> [ 360.451314] [<ffffffff81725b6c>] schedule_timeout+0x1dc/0x260
> [ 360.451317] [<ffffffff81722f69>] ? _cond_resched+0x29/0x40
> [ 360.451320] [<ffffffff81723818>] ? wait_for_completion+0x28/0x160
> [ 360.451325] [<ffffffff811081a7>] ? queue_stop_cpus_work+0xc7/0xe0
> [ 360.451327] [<ffffffff81723896>] wait_for_completion+0xa6/0x160
> [ 360.451331] [<ffffffff81099980>] ? wake_up_state+0x20/0x20
> [ 360.451335] [<ffffffff810d0ecc>] _rcu_barrier+0x20c/0x480
> [ 360.451338] [<ffffffff810d1195>] rcu_barrier+0x15/0x20
> [ 360.451342] [<ffffffff81625010>] netdev_run_todo+0x60/0x300
> [ 360.451345] [<ffffffff8162f9ee>] rtnl_unlock+0xe/0x10
> [ 360.451353] [<ffffffffa01ffcc5>] internal_dev_destroy+0x55/0x80 [openvswitch]
> [ 360.451358] [<ffffffffa01ff622>] ovs_vport_del+0x32/0x40 [openvswitch]
> [ 360.451362] [<ffffffffa01f8dd0>] ovs_dp_detach_port+0x30/0x40 [openvswitch]
> [ 360.451366] [<ffffffffa01f8ea5>] ovs_vport_cmd_del+0xc5/0x110 [openvswitch]
> [ 360.451370] [<ffffffff81651d75>] genl_family_rcv_msg+0x1a5/0x3c0
> [ 360.451373] [<ffffffff81651f90>] ? genl_family_rcv_msg+0x3c0/0x3c0
> [ 360.451376] [<ffffffff81652021>] genl_rcv_msg+0x91/0xd0
> [ 360.451379] [<ffffffff81650091>] netlink_rcv_skb+0xc1/0xe0
> [ 360.451381] [<ffffffff816505bc>] genl_rcv+0x2c/0x40
> [ 360.451384] [<ffffffff8164f626>] netlink_unicast+0xf6/0x200
> [ 360.451387] [<ffffffff8164fa4d>] netlink_sendmsg+0x31d/0x780
> [ 360.451390] [<ffffffff8164ca74>] ? netlink_rcv_wake+0x44/0x60
> [ 360.451394] [<ffffffff81606a53>] sock_sendmsg+0x93/0xd0
> [ 360.451399] [<ffffffff81337700>] ? apparmor_capable+0x60/0x60
> [ 360.451402] [<ffffffff81614f27>] ? verify_iovec+0x47/0xd0
> [ 360.451406] [<ffffffff81606e79>] ___sys_sendmsg+0x399/0x3b0
> [ 360.451410] [<ffffffff812598a2>] ? kernfs_seq_stop_active+0x32/0x40
> [ 360.451414] [<ffffffff8101c385>] ? native_sched_clock+0x35/0x90
> [ 360.451417] [<ffffffff8101c385>] ? native_sched_clock+0x35/0x90
> [ 360.451419] [<ffffffff8101c3e9>] ? sched_clock+0x9/0x10
> [ 360.451424] [<ffffffff811277fc>] ? acct_account_cputime+0x1c/0x20
> [ 360.451427] [<ffffffff8109ce6b>] ? account_user_time+0x8b/0xa0
> [ 360.451431] [<ffffffff81200bd5>] ? __fget_light+0x25/0x70
> [ 360.451434] [<ffffffff81607c02>] __sys_sendmsg+0x42/0x80
> [ 360.451437] [<ffffffff81607c52>] SyS_sendmsg+0x12/0x20
> [ 360.451440] [<ffffffff81727464>] tracesys_phase2+0xd8/0xdd
> [ 360.451442] rcu_show_nocb_setup(): rcu_sched nocb state:
> [ 360.456737] 0: ffff88013fc0e600 l:ffff88013fc0e600 n:ffff88013fc8e600 ...
> [ 360.463676] 1: ffff88013fc8e600 l:ffff88013fc0e600 n: (null) ...
> [ 360.470614] 2: ffff88013fd0e600 l:ffff88013fd0e600 n:ffff88013fd8e600 N..
> [ 360.477554] 3: ffff88013fd8e600 l:ffff88013fd0e600 n: (null) N..

Hmmm... It sure looks like we have some callbacks stuck here. I clearly
need to take a hard look at the sleep/wakeup code.

Thank you for running this!!!

Thanx, Paul

> [ 360.484494] rcu_show_nocb_setup(): rcu_bh nocb state:
> [ 360.489529] 0: ffff88013fc0e3c0 l:ffff88013fc0e3c0 n:ffff88013fc8e3c0 ...
> [ 360.496469] 1: ffff88013fc8e3c0 l:ffff88013fc0e3c0 n: (null) .G.
> [ 360.503407] 2: ffff88013fd0e3c0 l:ffff88013fd0e3c0 n:ffff88013fd8e3c0 ...
> [ 360.510346] 3: ffff88013fd8e3c0 l:ffff88013fd0e3c0 n: (null) ...
>
> ---
> -Jay Vosburgh, jay.vosburgh@xxxxxxxxxxxxx
> --
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