From: Jay Vosburgh <jay.vosburgh@canonical.com>
To: paulmck@linux.vnet.ibm.com
Cc: Yanko Kaneti <yaneti@declera.com>,
Josh Boyer <jwboyer@fedoraproject.org>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Cong Wang <cwang@twopensource.com>, Kevin Fenzi <kevin@scrye.com>,
netdev <netdev@vger.kernel.org>,
"Linux-Kernel@Vger. Kernel. Org" <linux-kernel@vger.kernel.org>,
mroos@linux.ee, tj@kernel.org
Subject: Re: localed stuck in recent 3.18 git in copy_net_ns?
Date: Fri, 24 Oct 2014 15:41:31 -0700 [thread overview]
Message-ID: <8988.1414190491@famine> (raw)
In-Reply-To: <20141024221602.GB4977@linux.vnet.ibm.com>
Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote:
>On Fri, Oct 24, 2014 at 03:02:04PM -0700, Jay Vosburgh wrote:
>> Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote:
>>
[...]
>> I've got an ftrace capture from unmodified -net, it looks like
>> this:
>>
>> ovs-vswitchd-902 [000] .... 471.778441: rcu_barrier: rcu_sched Begin cpu -1 remaining 0 # 0
>> ovs-vswitchd-902 [000] .... 471.778452: rcu_barrier: rcu_sched Check cpu -1 remaining 0 # 0
>> ovs-vswitchd-902 [000] .... 471.778452: rcu_barrier: rcu_sched Inc1 cpu -1 remaining 0 # 1
>> ovs-vswitchd-902 [000] .... 471.778453: rcu_barrier: rcu_sched OnlineNoCB cpu 0 remaining 1 # 1
>> ovs-vswitchd-902 [000] .... 471.778453: rcu_barrier: rcu_sched OnlineNoCB cpu 1 remaining 2 # 1
>> ovs-vswitchd-902 [000] .... 471.778453: rcu_barrier: rcu_sched OnlineNoCB cpu 2 remaining 3 # 1
>> ovs-vswitchd-902 [000] .... 471.778454: rcu_barrier: rcu_sched OnlineNoCB cpu 3 remaining 4 # 1
>
>OK, so it looks like your system has four CPUs, and rcu_barrier() placed
>callbacks on them all.
No, the system has only two CPUs. It's an Intel Core 2 Duo
E8400, and /proc/cpuinfo agrees that there are only 2. There is a
potentially relevant-sounding message early in dmesg that says:
[ 0.000000] smpboot: Allowing 4 CPUs, 2 hotplug CPUs
>> ovs-vswitchd-902 [000] .... 471.778454: rcu_barrier: rcu_sched Inc2 cpu -1 remaining 4 # 2
>
>The above removes the extra count used to avoid races between posting new
>callbacks and completion of previously posted callbacks.
>
>> rcuos/0-9 [000] ..s. 471.793150: rcu_barrier: rcu_sched CB cpu -1 remaining 3 # 2
>> rcuos/1-18 [001] ..s. 471.793308: rcu_barrier: rcu_sched CB cpu -1 remaining 2 # 2
>
>Two of the four callbacks fired, but the other two appear to be AWOL.
>And rcu_barrier() won't return until they all fire.
>
>> I let it sit through several "hung task" cycles but that was all
>> there was for rcu:rcu_barrier.
>>
>> I should have ftrace with the patch as soon as the kernel is
>> done building, then I can try the below patch (I'll start it building
>> now).
>
>Sounds very good, looking forward to hearing of the results.
Going to bounce it for ftrace now, but the cpu count mismatch
seemed important enough to mention separately.
-J
---
-Jay Vosburgh, jay.vosburgh@canonical.com
next prev parent reply other threads:[~2014-10-24 22:41 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-20 20:15 localed stuck in recent 3.18 git in copy_net_ns? Kevin Fenzi
2014-10-20 20:43 ` Dave Jones
2014-10-20 20:53 ` Kevin Fenzi
2014-10-21 21:12 ` Kevin Fenzi
2014-10-22 17:12 ` Josh Boyer
2014-10-22 17:37 ` Cong Wang
2014-10-22 17:49 ` Josh Boyer
2014-10-22 17:53 ` Eric W. Biederman
2014-10-22 18:11 ` Paul E. McKenney
2014-10-22 18:25 ` Eric W. Biederman
2014-10-22 18:55 ` Paul E. McKenney
2014-10-22 19:33 ` Josh Boyer
2014-10-22 22:40 ` Yanko Kaneti
2014-10-22 23:24 ` Paul E. McKenney
2014-10-23 6:09 ` Yanko Kaneti
2014-10-23 12:27 ` Paul E. McKenney
2014-10-23 15:33 ` Paul E. McKenney
[not found] ` <CA+5PVA4H6EAf6cBc4a_8W8x4Mgppjc5GsskKaCRry2jq+LP+FA@mail.gmail.com>
2014-10-23 16:28 ` Paul E. McKenney
2014-10-23 19:51 ` Yanko Kaneti
2014-10-23 20:05 ` Paul E. McKenney
2014-10-23 21:45 ` Yanko Kaneti
2014-10-23 22:04 ` Paul E. McKenney
2014-10-24 4:48 ` Jay Vosburgh
2014-10-24 14:50 ` Paul E. McKenney
2014-10-24 18:20 ` Jay Vosburgh
2014-10-24 18:33 ` Paul E. McKenney
2014-10-24 9:08 ` Yanko Kaneti
2014-10-24 15:40 ` Paul E. McKenney
2014-10-24 16:29 ` Yanko Kaneti
2014-10-24 16:54 ` Paul E. McKenney
2014-10-24 17:09 ` Yanko Kaneti
2014-10-24 17:20 ` Paul E. McKenney
2014-10-24 17:35 ` Yanko Kaneti
2014-10-24 18:32 ` Paul E. McKenney
2014-10-24 18:49 ` Jay Vosburgh
2014-10-24 18:57 ` Paul E. McKenney
2014-10-24 20:15 ` Paul E. McKenney
2014-10-24 21:25 ` Yanko Kaneti
2014-10-24 21:49 ` Paul E. McKenney
2014-10-24 22:02 ` Jay Vosburgh
2014-10-24 22:16 ` Paul E. McKenney
2014-10-24 22:41 ` Jay Vosburgh [this message]
2014-10-24 22:34 ` Jay Vosburgh
2014-10-24 22:59 ` Paul E. McKenney
2014-10-24 23:05 ` Paul E. McKenney
2014-10-25 0:20 ` Jay Vosburgh
2014-10-25 2:03 ` Paul E. McKenney
2014-10-25 4:33 ` Jay Vosburgh
2014-10-25 5:16 ` Paul E. McKenney
2014-10-25 16:38 ` Jay Vosburgh
2014-10-25 18:18 ` Paul E. McKenney
2014-10-27 17:45 ` Paul E. McKenney
2014-10-27 20:43 ` Jay Vosburgh
2014-10-27 21:07 ` Paul E. McKenney
2014-10-28 8:12 ` Yanko Kaneti
2014-10-28 12:50 ` Paul E. McKenney
2014-10-28 13:00 ` Yanko Kaneti
2014-10-28 15:54 ` Kevin Fenzi
2014-10-28 16:15 ` Paul E. McKenney
2014-10-25 12:09 ` Yanko Kaneti
2014-10-25 13:38 ` Paul E. McKenney
2014-10-22 17:59 ` Paul E. McKenney
2014-10-22 18:03 ` Josh Boyer
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