From: Mark Rutland <mark.rutland@arm.com>
To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Marco Elver <elver@google.com>, Will Deacon <will@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Anders Roxell <anders.roxell@linaro.org>,
Andrew Morton <akpm@linux-foundation.org>,
Alexander Potapenko <glider@google.com>,
Dmitry Vyukov <dvyukov@google.com>, Jann Horn <jannh@google.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
kasan-dev <kasan-dev@googlegroups.com>,
rcu@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>,
Tejun Heo <tj@kernel.org>, Lai Jiangshan <jiangshanlai@gmail.com>,
linux-arm-kernel@lists.infradead.org, boqun.feng@gmail.com,
tglx@linutronix.de
Subject: Re: linux-next: stall warnings and deadlock on Arm64 (was: [PATCH] kfence: Avoid stalling...)
Date: Tue, 24 Nov 2020 19:43:08 +0000 [thread overview]
Message-ID: <20201124194308.GC8957@C02TD0UTHF1T.local> (raw)
In-Reply-To: <20201124150146.GH1437@paulmck-ThinkPad-P72>
On Tue, Nov 24, 2020 at 07:01:46AM -0800, Paul E. McKenney wrote:
> On Tue, Nov 24, 2020 at 03:03:10PM +0100, Marco Elver wrote:
> > [ 91.184432] =============================
> > [ 91.188301] WARNING: suspicious RCU usage
> > [ 91.192316] 5.10.0-rc4-next-20201119-00002-g51c2bf0ac853 #25 Tainted: G W
> > [ 91.197536] -----------------------------
> > [ 91.201431] kernel/trace/trace_preemptirq.c:78 RCU not watching trace_hardirqs_off()!
> > [ 91.206546]
> > [ 91.206546] other info that might help us debug this:
> > [ 91.206546]
> > [ 91.211790]
> > [ 91.211790] rcu_scheduler_active = 2, debug_locks = 0
> > [ 91.216454] RCU used illegally from extended quiescent state!
> > [ 91.220890] no locks held by swapper/0/0.
> > [ 91.224712]
> > [ 91.224712] stack backtrace:
> > [ 91.228794] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G W 5.10.0-rc4-next-20201119-00002-g51c2bf0ac853 #25
> > [ 91.234877] Hardware name: linux,dummy-virt (DT)
> > [ 91.239032] Call trace:
> > [ 91.242587] dump_backtrace+0x0/0x240
> > [ 91.246500] show_stack+0x34/0x88
> > [ 91.250295] dump_stack+0x140/0x1bc
> > [ 91.254159] lockdep_rcu_suspicious+0xe4/0xf8
> > [ 91.258332] trace_hardirqs_off+0x214/0x330
> > [ 91.262462] trace_graph_return+0x1ac/0x1d8
> > [ 91.266564] ftrace_return_to_handler+0xa4/0x170
> > [ 91.270809] return_to_handler+0x1c/0x38
> > [ 91.274826] default_idle_call+0x94/0x38c
> > [ 91.278869] do_idle+0x240/0x290
> > [ 91.282633] rest_init+0x1e8/0x2dc
> > [ 91.286529] arch_call_rest_init+0x1c/0x28
> > [ 91.290585] start_kernel+0x638/0x670
> This looks like tracing in the idle loop in a place where RCU is not
> watching. Historically, this has been addressed by using _rcuidle()
> trace events, but the portion of the idle loop that RCU is watching has
> recently increased. Last I checked, there were still a few holdouts (that
> would splat like this) in x86, though perhaps those have since been fixed.
Yup! I think this is a latent issue my debug hacks revealed (in addition
to a couple of other issues in the idle path), and still affects x86 and
others. It's only noticeable if you hack trace_hardirqs_{on,off}() to
check rcu_is_watching(), which I had at the tip of my tree.
AFAICT, the issue is that arch_cpu_idle() can be dynamically traced with
ftrace, and hence the tracing code can unexpectedly run without RCU
watching. Since that's dynamic tracing, we can avoid it by marking
arch_cpu_idle() and friends as noinstr.
I'll see about getting this fixed before we upstream the debug hack.
Thanks,
Mark.
next prev parent reply other threads:[~2020-11-24 19:43 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-10 13:53 [PATCH] kfence: Avoid stalling work queue task without allocations Marco Elver
2020-11-10 14:25 ` Dmitry Vyukov
2020-11-10 14:53 ` Marco Elver
2020-11-10 23:23 ` Anders Roxell
2020-11-11 8:29 ` Marco Elver
2020-11-11 13:38 ` Marco Elver
2020-11-11 18:05 ` Steven Rostedt
2020-11-11 18:23 ` Paul E. McKenney
2020-11-11 18:34 ` Marco Elver
2020-11-11 19:21 ` Paul E. McKenney
2020-11-11 20:21 ` Marco Elver
2020-11-12 0:11 ` Paul E. McKenney
2020-11-12 12:49 ` Marco Elver
2020-11-12 16:14 ` Marco Elver
2020-11-12 17:54 ` Paul E. McKenney
2020-11-12 18:12 ` Marco Elver
2020-11-12 20:00 ` Paul E. McKenney
2020-11-13 11:06 ` Marco Elver
2020-11-13 17:20 ` Paul E. McKenney
2020-11-13 17:57 ` Paul E. McKenney
2020-11-17 10:52 ` Marco Elver
2020-11-17 18:29 ` Paul E. McKenney
2020-11-18 22:56 ` Marco Elver
2020-11-18 23:38 ` Paul E. McKenney
2020-11-19 12:53 ` Marco Elver
2020-11-19 15:14 ` Paul E. McKenney
2020-11-19 17:02 ` Marco Elver
2020-11-19 18:48 ` Paul E. McKenney
2020-11-19 19:38 ` linux-next: stall warnings and deadlock on Arm64 (was: [PATCH] kfence: Avoid stalling...) Marco Elver
2020-11-19 21:35 ` Paul E. McKenney
2020-11-19 22:53 ` Will Deacon
2020-11-20 10:30 ` Mark Rutland
2020-11-20 14:03 ` Marco Elver
2020-11-23 19:32 ` Mark Rutland
2020-11-24 14:03 ` Marco Elver
2020-11-24 15:01 ` Paul E. McKenney
2020-11-24 19:43 ` Mark Rutland [this message]
2020-11-24 20:32 ` Steven Rostedt
2020-11-24 19:30 ` Mark Rutland
2020-11-25 9:45 ` Marco Elver
2020-11-25 10:28 ` Mark Rutland
2020-11-20 14:19 ` Marco Elver
2020-11-20 14:39 ` Paul E. McKenney
2020-11-20 15:22 ` Mark Rutland
2020-11-20 17:38 ` Paul E. McKenney
2020-11-20 18:02 ` Mark Rutland
2020-11-20 18:57 ` Paul E. McKenney
2020-11-20 15:26 ` Steven Rostedt
2020-11-20 18:17 ` Marco Elver
2020-11-20 18:57 ` Steven Rostedt
2020-11-20 19:16 ` Steven Rostedt
2020-11-20 19:22 ` Marco Elver
2020-11-20 19:27 ` [PATCH] kfence: Avoid stalling work queue task without allocations Steven Rostedt
2020-11-23 15:27 ` Marco Elver
2020-11-23 16:28 ` Steven Rostedt
2020-11-23 16:36 ` Steven Rostedt
2020-11-23 18:53 ` Marco Elver
2020-11-23 18:42 ` Steven Rostedt
2020-11-24 2:59 ` Boqun Feng
2020-11-24 3:44 ` Paul E. McKenney
2020-11-11 18:21 ` Paul E. McKenney
2020-11-11 15:01 ` Anders Roxell
2020-11-11 15:22 ` Marco Elver
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