From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Dave Jones <davej@redhat.com>,
Linux Kernel <linux-kernel@vger.kernel.org>,
htejun@gmail.com
Subject: Re: rcu_preempt detected stalls.
Date: Thu, 23 Oct 2014 12:38:07 -0700 [thread overview]
Message-ID: <20141023193807.GZ4977@linux.vnet.ibm.com> (raw)
In-Reply-To: <20141023191319.GA5137@redhat.com>
On Thu, Oct 23, 2014 at 09:13:19PM +0200, Oleg Nesterov wrote:
> On 10/23, Paul E. McKenney wrote:
> >
> > On Mon, Oct 13, 2014 at 01:35:04PM -0400, Dave Jones wrote:
> > > Today in "rcu stall while fuzzing" news:
> > >
> > > INFO: rcu_preempt detected stalls on CPUs/tasks:
> > > Tasks blocked on level-0 rcu_node (CPUs 0-3): P766 P646
> > > Tasks blocked on level-0 rcu_node (CPUs 0-3): P766 P646
> > > (detected by 0, t=6502 jiffies, g=75434, c=75433, q=0)
> > > trinity-c342 R running task 13384 766 32295 0x00000000
> > > ffff880068943d58 0000000000000002 0000000000000002 ffff880193c8c680
> > > 00000000001d4100 0000000000000000 ffff880068943fd8 00000000001d4100
> > > ffff88024302c680 ffff880193c8c680 ffff880068943fd8 0000000000000000
> > > Call Trace:
> > > [<ffffffff888368e2>] preempt_schedule_irq+0x52/0xb0
> > > [<ffffffff8883df10>] retint_kernel+0x20/0x30
> > > [<ffffffff880d9424>] ? lock_acquire+0xd4/0x2b0
> > > [<ffffffff8808d495>] ? kill_pid_info+0x5/0x130
> > > [<ffffffff8808d4d5>] kill_pid_info+0x45/0x130
> > > [<ffffffff8808d495>] ? kill_pid_info+0x5/0x130
> > > [<ffffffff8808d6d2>] SYSC_kill+0xf2/0x2f0
> > > [<ffffffff8808d67b>] ? SYSC_kill+0x9b/0x2f0
> > > [<ffffffff8819c2b7>] ? context_tracking_user_exit+0x57/0x280
> > > [<ffffffff880136bd>] ? syscall_trace_enter+0x13d/0x310
> > > [<ffffffff8808fd9e>] SyS_kill+0xe/0x10
> > > [<ffffffff8883d3a4>] tracesys+0xdd/0xe2
> >
> > Well, there is a loop in kill_pid_info(). I am surprised that it
> > would loop indefinitely, but if it did, you would certainly get
> > RCU CPU stalls. Please see patch below, adding Oleg for his thoughts.
>
> Yes, this loops should not be a problem, we only restart if we race with
> a multi-threaded exec from a non-leader thread.
>
> But I already saw a couple of bug-reports which look as a task_struct
> corruption (->signal/creds == NULL), looks like something was broken
> recently. Perhaps an unbalanced put_task_struct...
>
> _Perhaps_ this is another case. If ->sighand was nullified then it will
> loop forever.
OK, so making each pass through the loop a separate RCU read-side critical
section might be considered to be suppressing notification of an error
condition?
Thanx, Paul
next prev parent reply other threads:[~2014-10-23 19:42 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-13 17:35 rcu_preempt detected stalls Dave Jones
2014-10-15 2:35 ` Sasha Levin
2014-10-23 18:39 ` Paul E. McKenney
2014-10-23 18:55 ` Sasha Levin
2014-10-23 19:58 ` Paul E. McKenney
2014-10-24 12:28 ` Sasha Levin
2014-10-24 16:13 ` Paul E. McKenney
2014-10-24 16:39 ` Sasha Levin
2014-10-27 21:13 ` Paul E. McKenney
2014-10-27 23:44 ` Paul E. McKenney
2014-10-27 23:44 ` Paul E. McKenney
2014-11-13 23:07 ` Paul E. McKenney
2014-11-13 23:07 ` Paul E. McKenney
2014-11-13 23:10 ` Sasha Levin
2014-11-13 23:10 ` Sasha Levin
2014-10-30 23:41 ` Sasha Levin
2014-10-23 18:32 ` Paul E. McKenney
2014-10-23 18:40 ` Dave Jones
2014-10-23 19:28 ` Paul E. McKenney
2014-10-23 19:37 ` Dave Jones
2014-10-23 19:52 ` Paul E. McKenney
2014-10-23 20:28 ` Dave Jones
2014-10-23 20:44 ` Paul E. McKenney
2014-10-23 19:13 ` Oleg Nesterov
2014-10-23 19:38 ` Paul E. McKenney [this message]
2014-10-23 19:53 ` Oleg Nesterov
2014-10-23 20:24 ` Paul E. McKenney
2014-10-23 21:13 ` Oleg Nesterov
2014-10-23 21:38 ` Paul E. McKenney
2014-10-25 3:16 ` Dâniel Fraga
2021-08-31 15:21 Jorge Ramirez-Ortiz, Foundries
2021-08-31 15:21 ` Jorge Ramirez-Ortiz, Foundries
2021-08-31 15:53 ` Paul E. McKenney
2021-08-31 15:53 ` Paul E. McKenney
2021-08-31 17:01 ` Zhouyi Zhou
2021-08-31 17:01 ` Zhouyi Zhou
2021-08-31 17:01 ` Zhouyi Zhou
2021-08-31 17:11 ` Zhouyi Zhou
2021-08-31 17:11 ` Zhouyi Zhou
2021-08-31 17:11 ` Zhouyi Zhou
2021-09-01 1:03 ` Zhouyi Zhou
2021-09-01 1:03 ` Zhouyi Zhou
2021-09-01 1:03 ` Zhouyi Zhou
2021-09-01 4:08 ` Neeraj Upadhyay
2021-09-01 6:47 ` Zhouyi Zhou
2021-09-01 6:47 ` Zhouyi Zhou
2021-09-01 6:47 ` Zhouyi Zhou
2021-09-01 8:23 ` Jorge Ramirez-Ortiz, Foundries
2021-09-01 8:23 ` Jorge Ramirez-Ortiz, Foundries
2021-09-01 9:17 ` Zhouyi Zhou
2021-09-01 9:17 ` Zhouyi Zhou
2021-09-01 9:17 ` Zhouyi Zhou
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