Re: åå: [kthread] a90477f0c9: WARNING:at_kernel/kthread.c:#kthread_queue_work

From: Petr Mladek
Date: Tue Jul 07 2020 - 05:47:28 EST

On Mon 2020-07-06 10:17:31, Zhang, Qiang wrote:
> Hi , Petr Mladek
> There some question for "Work could not be queued when worker being destroyed" patch,
>
> when in "spi_init_queue" func :
> "kthread_init_worker(&ctlr->kworker); (worker->task = NULL)
> ctlr->kworker_task = kthread_run(kthread_worker_fn, &ctlr->kworker,
> "%s", dev_name(&ctlr->dev)); "

I see. I have missed that there are some kthread_worker users that
start the worker this way. They rely on the fact that
worker->task is set also by kthread_worker_fn.

The proper solution is to start the worker using either
kthread_create_worker() or kthread_create_worker_on_cpu().
They set worker->task immediately.

It means that more work is needed:

1. Convert all users that start the kthread_worker via
kthread_worker_fn to use either kthread_create_worker()
or kthread_create_worker_on_cpu().

2. Remove kthread_worker_fn declaration from include/linux/kthread.h
to prevent starting the worker the temporary way.

In the same patch, also the assignment to worker->task and
the FIXME might get removed from kthread_worker_fn().


3. Finally, it should be safe to add the WARN_ON() into
queuing_blocked().

Best Regards,
Petr

>
> in "spi_start_queue" func:
> "kthread_queue_work(&ctlr->kworker, &ctlr->pump_messages);"
>
> Becasue the kthread_worker_fn is not begin running, if queue work to worker,
> the "!worker->task" = true, trigger WARN.
>
> Are Need to add judgment " test_bit(KTHREAD_SHOULD_STOP, &to_kthread(current)->flags) && WARN_ON(!worker->task)" in queuing_blocked func ?
>
> Zhang Qiang
>
>
>
>
> ________________________________________
> åää: kernel test robot <rong.a.chen@xxxxxxxxx>
> åéæé: 2020å7æ6æ 17:38
> æää: Zhang, Qiang
> æé: lkp@xxxxxxxxxxxx
> äé: [kthread] a90477f0c9: WARNING:at_kernel/kthread.c:#kthread_queue_work
>
> Greeting,
>
> FYI, we noticed the following commit (built with gcc-7):
>
> commit: a90477f0c956621eb0dd69f0abfb6066ad8fbef7 ("kthread: work could not be queued when worker being destroyed")
> https://github.com/hnaz/linux-mm master
>
> in testcase: trinity
> with following parameters:
>
> runtime: 300s
>
> test-description: Trinity is a linux system call fuzz tester.
> test-url: http://codemonkey.org.uk/projects/trinity/
>
>
> on test machine: qemu-system-i386 -enable-kvm -cpu SandyBridge -smp 2 -m 16G
>
> caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):
>
>
> +-------------------------------------------------+------------+------------+
> | | 85c6127e06 | a90477f0c9 |
> +-------------------------------------------------+------------+------------+
> | boot_successes | 6 | 0 |
> | boot_failures | 0 | 30 |
> | WARNING:at_kernel/kthread.c:#kthread_queue_work | 0 | 30 |
> | EIP:kthread_queue_work | 0 | 30 |
> | BUG:kernel_hang_in_test_stage | 0 | 2 |
> +-------------------------------------------------+------------+------------+
>
>
> If you fix the issue, kindly add following tag
> Reported-by: kernel test robot <rong.a.chen@xxxxxxxxx>
>
>
> [ 5.554282] WARNING: CPU: 0 PID: 1 at kernel/kthread.c:817 kthread_queue_work+0xf8/0x120
> [ 5.556204] Modules linked in:
> [ 5.556204] CPU: 0 PID: 1 Comm: swapper Tainted: G S 5.8.0-rc3-00014-ga90477f0c9566 #1
> [ 5.556204] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
> [ 5.556204] EIP: kthread_queue_work+0xf8/0x120
> [ 5.556204] Code: 00 59 e9 67 ff ff ff 8d 76 00 8b 4e 10 85 c9 75 a6 8d 4b 28 89 f2 89 d8 bf 01 00 00 00 e8 f0 f5 ff ff eb 93 8d b6 00 00 00 00 <0f> 0b 6a 00 31 c9 ba 01 00 00 00 b8 08 6c 64 c3 e8 f3 04 0b 00 5b
> [ 5.556204] EAX: 00000000 EBX: eeff538c ECX: 00000000 EDX: 00000001
> [ 5.556204] ESI: eeff53d0 EDI: 00000000 EBP: f5edde70 ESP: f5edde5c
> [ 5.556204] DS: 007b ES: 007b FS: 0000 GS: 0000 SS: 0068 EFLAGS: 00010046
> [ 5.556204] CR0: 80050033 CR2: b7eda844 CR3: 038ae000 CR4: 000406d0
> [ 5.556204] Call Trace:
> [ 5.556204] spi_start_queue+0x50/0x70
> [ 5.556204] spi_register_controller+0x642/0xa80
> [ 5.556204] ? kobject_get+0x54/0xf0
> [ 5.556204] ? parport_pc_platform_probe+0x10/0x10
> [ 5.556204] spi_bitbang_start+0x2f/0x70
> [ 5.556204] ? parport_pc_platform_probe+0x10/0x10
> [ 5.556204] butterfly_attach+0x164/0x2c0
> [ 5.556204] ? driver_detach+0x30/0x30
> [ 5.556204] port_check+0x1c/0x30
> [ 5.556204] bus_for_each_dev+0x5a/0x90
> [ 5.556204] __parport_register_driver+0x76/0xa0
> [ 5.556204] ? driver_detach+0x30/0x30
> [ 5.556204] ? spi_engine_driver_init+0x16/0x16
> [ 5.556204] butterfly_init+0x19/0x1b
> [ 5.556204] do_one_initcall+0x79/0x310
> [ 5.556204] ? parse_args+0x70/0x420
> [ 5.556204] ? rcu_read_lock_sched_held+0x2f/0x50
> [ 5.556204] ? trace_initcall_level+0x95/0xc7
> [ 5.556204] ? kernel_init_freeable+0x129/0x19f
> [ 5.556204] kernel_init_freeable+0x148/0x19f
> [ 5.556204] ? rest_init+0x100/0x100
> [ 5.556204] kernel_init+0xd/0xf0
> [ 5.556204] ret_from_fork+0x1c/0x28
> [ 5.556204] irq event stamp: 8620410
> [ 5.556204] hardirqs last enabled at (8620409): [<c2675daa>] _raw_spin_unlock_irqrestore+0x2a/0x50
> [ 5.556204] hardirqs last disabled at (8620410): [<c2675bb4>] _raw_spin_lock_irqsave+0x14/0x40
> [ 5.556204] softirqs last enabled at (8620262): [<c2677900>] __do_softirq+0x2e0/0x480
> [ 5.556204] softirqs last disabled at (8620249): [<c1023cf5>] call_on_stack+0x45/0x50
> [ 5.556204] ---[ end trace 184061a442b5fd6f ]---
>
>
> To reproduce:
>
> # build kernel
> cd linux
> cp config-5.8.0-rc3-00014-ga90477f0c9566 .config
> make HOSTCC=gcc-7 CC=gcc-7 ARCH=i386 olddefconfig prepare modules_prepare bzImage
>
> git clone https://github.com/intel/lkp-tests.git
> cd lkp-tests
> bin/lkp qemu -k <bzImage> job-script # job-script is attached in this email
>
>
>
> Thanks,
> Rong Chen