From: Marco Elver <elver@google.com>
To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: 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>,
Mark Rutland <mark.rutland@arm.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
Subject: Re: linux-next: stall warnings and deadlock on Arm64 (was: [PATCH] kfence: Avoid stalling...)
Date: Fri, 20 Nov 2020 15:19:28 +0100 [thread overview]
Message-ID: <20201120141928.GB3120165@elver.google.com> (raw)
In-Reply-To: <20201119213512.GB1437@paulmck-ThinkPad-P72>
On Thu, Nov 19, 2020 at 01:35PM -0800, Paul E. McKenney wrote:
> On Thu, Nov 19, 2020 at 08:38:19PM +0100, Marco Elver wrote:
> > On Thu, Nov 19, 2020 at 10:48AM -0800, Paul E. McKenney wrote:
> > > On Thu, Nov 19, 2020 at 06:02:59PM +0100, Marco Elver wrote:
>
> [ . . . ]
>
> > > > I can try bisection again, or reverting some commits that might be
> > > > suspicious? But we'd need some selection of suspicious commits.
> > >
> > > The report claims that one of the rcu_node ->lock fields is held
> > > with interrupts enabled, which would indeed be bad. Except that all
> > > of the stack traces that it shows have these locks held within the
> > > scheduling-clock interrupt handler. Now with the "rcu: Don't invoke
> > > try_invoke_on_locked_down_task() with irqs disabled" but without the
> > > "sched/core: Allow try_invoke_on_locked_down_task() with irqs disabled"
> > > commit, I understand why. With both, I don't see how this happens.
> >
> > I'm at a loss, but happy to keep bisecting and trying patches. I'm also
> > considering:
> >
> > Is it the compiler? Probably not, I tried 2 versions of GCC.
> >
> > Can we trust lockdep to precisely know IRQ state? I know there's
> > been some recent work around this, but hopefully we're not
> > affected here?
> >
> > Is QEMU buggy?
> >
> > > At this point, I am reduced to adding lockdep_assert_irqs_disabled()
> > > calls at various points in that code, as shown in the patch below.
> > >
> > > At this point, I would guess that your first priority would be the
> > > initial bug rather than this following issue, but you never know, this
> > > might well help diagnose the initial bug.
> >
> > I don't mind either way. I'm worried deadlocking the whole system might
> > be worse.
>
> Here is another set of lockdep_assert_irqs_disabled() calls on the
> off-chance that they actually find something.
>
> Thanx, Paul
>
> ------------------------------------------------------------------------
>
> commit bcca5277df3f24db15e15ccc8b05ecf346d05169
> Author: Paul E. McKenney <paulmck@kernel.org>
> Date: Thu Nov 19 13:30:33 2020 -0800
>
> rcu: Add lockdep_assert_irqs_disabled() to raw_spin_unlock_rcu_node() macros
None of those triggered either.
I found that disabling ftrace for some of kernel/rcu (see below) solved
the stalls (and any mention of deadlocks as a side-effect I assume),
resulting in successful boot.
Does that provide any additional clues? I tried to narrow it down to 1-2
files, but that doesn't seem to work.
Thanks,
-- Marco
------ >8 ------
diff --git a/kernel/rcu/Makefile b/kernel/rcu/Makefile
index 0cfb009a99b9..678b4b094f94 100644
--- a/kernel/rcu/Makefile
+++ b/kernel/rcu/Makefile
@@ -3,6 +3,13 @@
# and is generally not a function of system call inputs.
KCOV_INSTRUMENT := n
+ifdef CONFIG_FUNCTION_TRACER
+CFLAGS_REMOVE_update.o = $(CC_FLAGS_FTRACE)
+CFLAGS_REMOVE_sync.o = $(CC_FLAGS_FTRACE)
+CFLAGS_REMOVE_srcutree.o = $(CC_FLAGS_FTRACE)
+CFLAGS_REMOVE_tree.o = $(CC_FLAGS_FTRACE)
+endif
+
ifeq ($(CONFIG_KCSAN),y)
KBUILD_CFLAGS += -g -fno-omit-frame-pointer
endif
next prev parent reply other threads:[~2020-11-20 14:19 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
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 [this message]
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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