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From: Anders Roxell <anders.roxell@linaro.org>
To: Marco Elver <elver@google.com>
Cc: 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>
Subject: Re: [PATCH] kfence: Avoid stalling work queue task without allocations
Date: Wed, 11 Nov 2020 16:01:33 +0100
Message-ID: <CADYN=9LtdW3Bs29VSq2ygnNcb3ub_UBLj8tZg5ff5Zvojr5FWg@mail.gmail.com> (raw)
In-Reply-To: <CANpmjNM8MZphvkTSo=KgCBXQ6fNY4qo6NZD5SBHjNse_L9i5FQ@mail.gmail.com>

On Wed, 11 Nov 2020 at 09:29, Marco Elver <elver@google.com> wrote:
>
> On Wed, 11 Nov 2020 at 00:23, Anders Roxell <anders.roxell@linaro.org> wrote:
> [...]
> >
> > I gave them a spin on next-20201105 [1] and on next-20201110 [2].
> >
> > I eventually got to a prompt on next-20201105.
> > However, I got to this kernel panic on the next-20201110:
> >
> > [...]
> > [ 1514.089966][    T1] Testing event system initcall: OK
> > [ 1514.806232][    T1] Running tests on all trace events:
> > [ 1514.857835][    T1] Testing all events:
> > [ 1525.503262][    C0] hrtimer: interrupt took 10902600 ns
> > [ 1623.861452][    C0] BUG: workqueue lockup - pool cpus=0 node=0
> > flags=0x0 nice=0 stuck for 65s!
> > [...]
> > [ 7823.104349][   T28]       Tainted: G        W
> > 5.10.0-rc3-next-20201110-00008-g8dc06700529d #3
> > [ 7833.206491][   T28] "echo 0 >
> > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> > [ 7840.750700][   T28] task:kworker/0:1     state:D stack:26640 pid:
> > 1872 ppid:     2 flags:0x00000428
> > [ 7875.642531][   T28] Workqueue: events toggle_allocation_gate
> > [ 7889.178334][   T28] Call trace:
> > [ 7897.066649][   T28]  __switch_to+0x1cc/0x1e0
> > [ 7905.326856][   T28]  0xffff00000f7077b0
> > [ 7928.354644][   T28] INFO: lockdep is turned off.
> > [ 7934.022572][   T28] Kernel panic - not syncing: hung_task: blocked tasks
> > [ 7934.032039][   T28] CPU: 0 PID: 28 Comm: khungtaskd Tainted: G
> >   W         5.10.0-rc3-next-20201110-00008-g8dc06700529d #3
> > [ 7934.045586][   T28] Hardware name: linux,dummy-virt (DT)
> > [ 7934.053677][   T28] Call trace:
> > [ 7934.060276][   T28]  dump_backtrace+0x0/0x420
> > [ 7934.067635][   T28]  show_stack+0x38/0xa0
> > [ 7934.091277][   T28]  dump_stack+0x1d4/0x278
> > [ 7934.098878][   T28]  panic+0x304/0x5d8
> > [ 7934.114923][   T28]  check_hung_uninterruptible_tasks+0x5e4/0x640
> > [ 7934.123823][   T28]  watchdog+0x138/0x160
> > [ 7934.131561][   T28]  kthread+0x23c/0x260
> > [ 7934.138590][   T28]  ret_from_fork+0x10/0x18
> > [ 7934.146631][   T28] Kernel Offset: disabled
> > [ 7934.153749][   T28] CPU features: 0x0240002,20002004
> > [ 7934.161476][   T28] Memory Limit: none
> > [ 7934.171272][   T28] ---[ end Kernel panic - not syncing: hung_task:
> > blocked tasks ]---
> >
> > Cheers,
> > Anders
> > [1] https://people.linaro.org/~anders.roxell/output-next-20201105-test.log
> > [2] https://people.linaro.org/~anders.roxell/output-next-20201110-test.log
>
> Thanks for testing. The fact that it passes on next-20201105 but not
> on 20201110 is strange. If you boot with KFENCE disabled (boot param
> kfence.sample_interval=0), does it boot?

This is my qemu cmdline with kfence.sample_interval=0
$ qemu-system-aarch64 --enable-kvm -cpu cortex-a53 -kernel
Image-20201110-test -serial stdio -monitor none -nographic -m 2G -M
virt -fsdev local,id=root,path=/srv/kvm/tmp/stretch/arm64-test,security_model=none,writeout=immediate
-device virtio-rng-pci -device
virtio-9p-pci,fsdev=root,mount_tag=/dev/root -append "root=/dev/root
rootfstype=9p rootflags=trans=virtio console=ttyAMA0,38400n8
earlycon=pl011,0x9000000 initcall_debug softlockup_panic=0
security=none kpti=no kfence.sample_interval=0"

This is the result, I managed to get to the prompt. see
https://people.linaro.org/~anders.roxell/output-next-20201110-test-2.log

Cheers,
Anders

>
> In your log [2] I see a number of "BUG: workqueue lockup ..." but that
> doesn't make sense, at least I don't think the KFENCE work item is
> causing this. It'd be interesting to bisect what changed between
> 20201105 and 20201110, but I have a suspicion that might take too
> long. Short of that, let me see if there are any changes between the 2
> that look like it might be causing this.
>
> Thanks,
> -- Marco

  parent reply index

Thread overview: 63+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-10 13:53 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
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 [this message]
2020-11-11 15:22       ` Marco Elver

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