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Sender: Guenter Roeck <groeck7@gmail.com>
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Date:   Thu, 7 Apr 2022 02:23:42 -0700
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Subject: Re: [BUG] hwmon: (adt7470) warning when removing the module
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To:     Armin Wolf <W_Armin@gmx.de>, Zheyu Ma <zheyuma97@gmail.com>,
        jdelvare@suse.com
Cc:     linux-hwmon@vger.kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
References: <CAMhUBjmTObCwaF=enLNkRSzxqSzK6KdkHf+4cWo5fqOO7B40iw@mail.gmail.com>
 <5f3a3672-6b99-7e24-9003-443c571f2dcc@gmx.de>
From:   Guenter Roeck <linux@roeck-us.net>
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On 4/6/22 22:01, Armin Wolf wrote:
> Am 07.04.22 um 05:17 schrieb Zheyu Ma:
> 
>> I found a bug when removing the adt7470 module.
>>
>> The following log can reveal it:
>>
>> [   18.459479] ------------[ cut here ]------------
>> [   18.459852] do not call blocking ops when !TASK_RUNNING; state=1
>> set at [<ffffffffa006052b>] adt7470_update_thread+0x7b/0x130 [adt7470]
>> [   18.460857] WARNING: CPU: 7 PID: 365 at kernel/sched/core.c:9660
>> __might_sleep+0x96/0xb0
>> [   18.461523] Modules linked in: adt7470(-)
>> [   18.464568] RIP: 0010:__might_sleep+0x96/0xb0
>> [   18.472577] Call Trace:
>> [   18.472778]  <TASK>
>> [   18.472957]  exit_signals+0x2f/0x3b0
>> [   18.473251]  do_exit+0xcd/0x18c0
>> [   18.473534]  ? __mutex_unlock_slowpath+0x1b8/0x740
>> [   18.473927]  kthread_exit+0x42/0x60
>> [   18.474212]  ? adt7470_detect+0x140/0x140 [adt7470]
>> [   18.474622]  kthread+0x272/0x2e0
>> [   18.474885]  ? adt7470_detect+0x140/0x140 [adt7470]
>> [   18.475277]  ? kthread_blkcg+0xa0/0xa0
>> [   18.475601]  ret_from_fork+0x22/0x30
>> [   18.475901]  </TASK>
>>
>> Regards,
>> Zheyu Ma
> 
> Please correct me if i am wrong, but i think the issue lies in adt7470_update_thread()
> leaving the kthread in TASK_INTERRUPTIBLE state when the second check for kthread_should_stop()
> returns true and causes the kthread to exit. Since kthread_exit() might sleep in exit_signals(),
> we get this warning.
> Maybe moving set_current_state(TASK_INTERRUPTIBLE) below the second check for kthread_should_stop()
> would fix the issue?
> 

Agreed. Care to send a patch ?

Thanks,
Guenter