From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Yanko Kaneti <yaneti@declera.com>
Cc: 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>,
jay.vosburgh@canonical.com, mroos@linux.ee, tj@kernel.org
Subject: Re: localed stuck in recent 3.18 git in copy_net_ns?
Date: Fri, 24 Oct 2014 14:49:27 -0700 [thread overview]
Message-ID: <20141024214927.GA4977@linux.vnet.ibm.com> (raw)
In-Reply-To: <20141024212557.GA15537@declera.com>
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.
Thanx, Paul
------------------------------------------------------------------------
rcu: Dump no-CBs CPU state at task-hung time
Strictly diagnostic commit for rcu_barrier() hang. Not for inclusion.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index 0e5366200154..34048140577b 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -157,4 +157,8 @@ static inline bool rcu_is_watching(void)
#endif /* #else defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) */
+static inline void rcu_show_nocb_setup(void)
+{
+}
+
#endif /* __LINUX_RCUTINY_H */
diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
index 52953790dcca..0b813bdb971b 100644
--- a/include/linux/rcutree.h
+++ b/include/linux/rcutree.h
@@ -97,4 +97,6 @@ extern int rcu_scheduler_active __read_mostly;
bool rcu_is_watching(void);
+void rcu_show_nocb_setup(void);
+
#endif /* __LINUX_RCUTREE_H */
diff --git a/kernel/hung_task.c b/kernel/hung_task.c
index 06db12434d72..e6e4d0f6b063 100644
--- a/kernel/hung_task.c
+++ b/kernel/hung_task.c
@@ -118,6 +118,7 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout)
" disables this message.\n");
sched_show_task(t);
debug_show_held_locks(t);
+ rcu_show_nocb_setup();
touch_nmi_watchdog();
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 240fa9094f83..6b373e79ce0e 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -1513,6 +1513,7 @@ rcu_torture_cleanup(void)
{
int i;
+ rcu_show_nocb_setup();
rcutorture_record_test_transition();
if (torture_cleanup_begin()) {
if (cur_ops->cb_barrier != NULL)
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 927c17b081c7..285b3f6fb229 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -2699,6 +2699,31 @@ static bool init_nocb_callback_list(struct rcu_data *rdp)
#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */
+void rcu_show_nocb_setup(void)
+{
+#ifdef CONFIG_RCU_NOCB_CPU
+ int cpu;
+ struct rcu_data *rdp;
+ struct rcu_state *rsp;
+
+ for_each_rcu_flavor(rsp) {
+ pr_alert("rcu_show_nocb_setup(): %s nocb state:\n", rsp->name);
+ for_each_possible_cpu(cpu) {
+ if (!rcu_is_nocb_cpu(cpu))
+ continue;
+ rdp = per_cpu_ptr(rsp->rda, cpu);
+ pr_alert("%3d: %p l:%p n:%p %c%c%c\n",
+ cpu,
+ rdp, rdp->nocb_leader, rdp->nocb_next_follower,
+ ".N"[!!rdp->nocb_head],
+ ".G"[!!rdp->nocb_gp_head],
+ ".F"[!!rdp->nocb_follower_head]);
+ }
+ }
+#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
+}
+EXPORT_SYMBOL_GPL(rcu_show_nocb_setup);
+
/*
* An adaptive-ticks CPU can potentially execute in kernel mode for an
* arbitrarily long period of time with the scheduling-clock tick turned
next prev parent reply other threads:[~2014-10-24 21:49 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 [this message]
2014-10-24 22:02 ` Jay Vosburgh
2014-10-24 22:16 ` Paul E. McKenney
2014-10-24 22:41 ` Jay Vosburgh
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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