From: "Paul E. McKenney" <paulmck@linux.ibm.com>
To: Joel Fernandes <joel@joelfernandes.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Steven Rostedt <rostedt@goodmis.org>, rcu <rcu@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Josh Triplett <josh@joshtriplett.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Lai Jiangshan <jiangshanlai@gmail.com>
Subject: Re: [RFC] Deadlock via recursive wakeup via RCU with threadirqs
Date: Thu, 27 Jun 2019 13:45:21 -0700 [thread overview]
Message-ID: <20190627204521.GA31499@linux.ibm.com> (raw)
In-Reply-To: <20190627183022.GZ26519@linux.ibm.com>
On Thu, Jun 27, 2019 at 11:30:22AM -0700, Paul E. McKenney wrote:
> On Thu, Jun 27, 2019 at 11:11:12AM -0700, Paul E. McKenney wrote:
> > On Thu, Jun 27, 2019 at 01:46:27PM -0400, Joel Fernandes wrote:
> > > On Thu, Jun 27, 2019 at 1:43 PM Joel Fernandes <joel@joelfernandes.org> wrote:
> > > >
> > > > On Thu, Jun 27, 2019 at 11:40 AM Sebastian Andrzej Siewior
> > > > <bigeasy@linutronix.de> wrote:
> > > > >
> > > > > On 2019-06-27 11:37:10 [-0400], Joel Fernandes wrote:
> > > > > > Sebastian it would be nice if possible to trace where the
> > > > > > t->rcu_read_unlock_special is set for this scenario of calling
> > > > > > rcu_read_unlock_special, to give a clear idea about whether it was
> > > > > > really because of an IPI. I guess we could also add additional RCU
> > > > > > debug fields to task_struct (just for debugging) to see where there
> > > > > > unlock_special is set.
> > > > > >
> > > > > > Is there a test to reproduce this, or do I just boot an intel x86_64
> > > > > > machine with "threadirqs" and run into it?
> > > > >
> > > > > Do you want to send me a patch or should I send you my kvm image which
> > > > > triggers the bug on boot?
> > > >
> > > > I could reproduce this as well just booting Linus tree with threadirqs
> > > > command line and running rcutorture. In 15 seconds or so it locks
> > > > up... gdb backtrace shows the recursive lock:
> > >
> > > Sorry that got badly wrapped, so I pasted it here:
> > > https://hastebin.com/ajivofomik.shell
> >
> > Which rcutorture scenario would that be? TREE03 is thus far refusing
> > to fail for me when run this way:
> >
> > $ tools/testing/selftests/rcutorture/bin/kvm.sh --cpus 8 --duration 5 --trust-make --configs "TREE03" --bootargs "threadirqs"
>
> Ah, but I was running -rcu. TREE03 fails at 38 seconds for me on v5.2.
>
> Now to find out which -rcu commit fixed it. Or at least made it much
> less probable, to Sebastian's point.
And it still works before this one:
a69987a515c8 ("rcu: Simplify rcu_read_unlock_special() deferred wakeups")
(This is included in the dev branch of the -rcu tree, and is
currently slated for v5.4.)
And it works at these commits:
0864f057b050 ("rcu: Use irq_work to get scheduler's attention in clean context")
385b599e8c04 ("rcu: Allow rcu_read_unlock_special() to raise_softirq() if in_irq()")
25102de65fdd ("rcu: Only do rcu_read_unlock_special() wakeups if expedited")
23634ebc1d94 ("rcu: Check for wakeup-safe conditions in rcu_read_unlock_special()")
I checked the last one twice, both completing without problems
other than false positives due to security-induced pointer
obfuscation. (These will be included in my v5.3 pull request.)
But not at this commit:
48d07c04b4cc ("rcu: Enable elimination of Tree-RCU softirq processing")
This gets RCU CPU stall warnings rather than the double wakeup
of ksoftirqd. Works fine without traceirqs.
v5.2-rc1 locks up hard at early boot (three of three attempts):
[ 2.525153] clocksource: Switched to clocksource tsc
[ 2.878858] random: fast init done
[ 2.881122] input: ImExPS/2 Generic Explorer Mouse as /devices/platform/i8042/serio1/input/input3
[ 2.884183] probe of serio1 returned 1 after 671008 usecs
[ 9.969474] hrtimer: interrupt took 3992554 ns
v5.1 gets the double wakeup of ksoftirqd.
So it looks like I need to get that pull request sent out, doesn't it? ;-)
Thanx, Paul
next prev parent reply other threads:[~2019-06-27 20:45 UTC|newest]
Thread overview: 78+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-26 13:54 [RFC] Deadlock via recursive wakeup via RCU with threadirqs Sebastian Andrzej Siewior
2019-06-26 16:25 ` Paul E. McKenney
2019-06-27 7:47 ` Sebastian Andrzej Siewior
2019-06-27 15:52 ` Paul E. McKenney
2019-06-27 14:24 ` Joel Fernandes
2019-06-27 14:34 ` Steven Rostedt
2019-06-27 15:30 ` Joel Fernandes
2019-06-27 15:37 ` Joel Fernandes
2019-06-27 15:40 ` Sebastian Andrzej Siewior
2019-06-27 15:42 ` Joel Fernandes
2019-06-27 17:43 ` Joel Fernandes
2019-06-27 17:46 ` Joel Fernandes
2019-06-27 18:11 ` Paul E. McKenney
2019-06-27 18:27 ` Joel Fernandes
2019-06-27 18:51 ` Joel Fernandes
2019-06-27 19:14 ` Paul E. McKenney
2019-06-27 19:15 ` Paul E. McKenney
2019-06-27 18:30 ` Paul E. McKenney
2019-06-27 20:45 ` Paul E. McKenney [this message]
2019-06-27 15:55 ` Paul E. McKenney
2019-06-27 16:47 ` Joel Fernandes
2019-06-27 17:38 ` Paul E. McKenney
2019-06-27 18:16 ` Joel Fernandes
2019-06-27 18:41 ` Paul E. McKenney
2019-06-27 20:17 ` Scott Wood
2019-06-27 20:36 ` Paul E. McKenney
2019-06-28 7:31 ` Byungchul Park
2019-06-28 7:43 ` Byungchul Park
2019-06-28 8:14 ` Byungchul Park
2019-06-28 8:24 ` Byungchul Park
2019-06-28 12:24 ` Paul E. McKenney
2019-06-28 9:10 ` Byungchul Park
2019-06-28 9:28 ` Byungchul Park
2019-06-28 12:21 ` Paul E. McKenney
2019-06-28 10:40 ` Byungchul Park
2019-06-28 12:27 ` Paul E. McKenney
2019-06-28 15:44 ` Steven Rostedt
2019-06-29 15:12 ` Andrea Parri
2019-06-29 16:55 ` Paul E. McKenney
2019-06-29 18:09 ` Andrea Parri
2019-06-29 18:21 ` Andrea Parri
2019-06-29 19:15 ` Paul E. McKenney
2019-06-29 19:35 ` Andrea Parri
2019-06-30 23:55 ` Byungchul Park
2019-06-28 14:15 ` Peter Zijlstra
2019-06-28 15:54 ` Paul E. McKenney
2019-06-28 16:04 ` Peter Zijlstra
2019-06-28 17:20 ` Paul E. McKenney
2019-07-01 9:42 ` Peter Zijlstra
2019-07-01 10:24 ` Sebastian Andrzej Siewior
2019-07-01 12:23 ` Paul E. McKenney
2019-07-01 14:00 ` Peter Zijlstra
2019-07-01 16:01 ` Paul E. McKenney
2019-06-28 20:01 ` Scott Wood
2019-07-01 9:45 ` Peter Zijlstra
2019-06-28 13:54 ` Peter Zijlstra
2019-06-28 15:30 ` Paul E. McKenney
2019-06-28 18:40 ` Sebastian Andrzej Siewior
2019-06-28 18:52 ` Paul E. McKenney
2019-06-28 19:24 ` Joel Fernandes
2019-06-28 20:04 ` Paul E. McKenney
2019-06-28 21:40 ` Joel Fernandes
2019-06-28 22:25 ` Paul E. McKenney
2019-06-28 23:12 ` Joel Fernandes
2019-06-29 0:06 ` Paul E. McKenney
2019-06-28 16:40 ` Joel Fernandes
2019-06-28 16:45 ` Joel Fernandes
2019-06-28 17:30 ` Paul E. McKenney
2019-06-28 17:41 ` Paul E. McKenney
2019-06-28 17:45 ` Sebastian Andrzej Siewior
2019-06-28 18:07 ` Joel Fernandes
2019-06-28 18:20 ` Sebastian Andrzej Siewior
2019-07-01 2:08 ` Joel Fernandes
2019-06-28 18:22 ` Paul E. McKenney
2019-06-28 19:29 ` Joel Fernandes
2019-06-28 20:06 ` Paul E. McKenney
2019-06-28 18:05 ` Joel Fernandes
2019-06-28 18:23 ` Paul E. McKenney
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