linux-kernel - Re: [PATCH] hungtask: add filter kthread/check comm

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Message-ID: <YKdv9hmRh+VxJrnH@dhcp22.suse.cz>
Date:   Fri, 21 May 2021 10:31:50 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     陈冠有 <chenguanyou9338@...il.com>
Cc:     Randy Dunlap <rdunlap@...radead.org>, linux-kernel@...r.kernel.org,
        akpm@...ux-foundation.org, Kees Cook <keescook@...omium.org>,
        lukas.bulwahn@...il.com, vbabka@...e.cz, gpiccoli@...onical.com,
        chenguanyou <chenguanyou@...omi.com>
Subject: Re: [PATCH] hungtask: add filter kthread/check comm

On Fri 21-05-21 14:38:06, 陈冠有 wrote:
> when we no skip kthread, exp log:
> 3,25164,832483138,-; (1)[67:khungtaskd]INFO: task amms_task:51 blocked for
> more than 120 seconds.
> 3,25165,832483169,-; (1)[67:khungtaskd]      Tainted: P S      W  O
>  4.14.186-g9d5f2ff-dirty #4
> 3,25166,832483186,-; (1)[67:khungtaskd]"echo 0 >
> /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> 6,25167,832483205,-; (1)[67:khungtaskd]amms_task       D    0    51      2
> 0x00000000
> 4,25168,832483232,-; (1)[67:khungtaskd]Call trace:
> 4,25169,832483268,-; (1)[67:khungtaskd] __switch_to+0x134/0x150
> 4,25170,832483297,-; (1)[67:khungtaskd] __schedule+0xd5c/0x1100
> 4,25171,832483318,-; (1)[67:khungtaskd] schedule+0x70/0x90
> 4,25172,832483343,-; (1)[67:khungtaskd] kthread+0xfc/0x18c
> 4,25173,832483365,-; (1)[67:khungtaskd] ret_from_fork+0x10/0x18
> 3,25174,832483482,-; (1)[67:khungtaskd]INFO: task mdrt_thread:123 blocked
> for more than 120 seconds.
> 3,25175,832483501,-; (1)[67:khungtaskd]      Tainted: P S      W  O
>  4.14.186-g9d5f2ff-dirty #4
> 3,25176,832483516,-; (1)[67:khungtaskd]"echo 0 >
> /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> 6,25177,832483533,-; (1)[67:khungtaskd]mdrt_thread     D    0   123      2
> 0x00000000
> 4,25178,832483555,-; (1)[67:khungtaskd]Call trace:
> 4,25179,832483574,-; (1)[67:khungtaskd] __switch_to+0x134/0x150
> 4,25180,832483595,-; (1)[67:khungtaskd] __schedule+0xd5c/0x1100
> 4,25181,832483615,-; (1)[67:khungtaskd] schedule+0x70/0x90
> 4,25182,832483635,-; (1)[67:khungtaskd] kthread+0xfc/0x18c
> 4,25183,832483655,-; (1)[67:khungtaskd] ret_from_fork+0x10/0x18
> 3,25184,832483737,-; (1)[67:khungtaskd]INFO: task scp_power_reset:227
> blocked for more than 120 seconds.

What are all these kernel threads doing and why it is ok to inhibit them
in the report.
-- 
Michal Hocko
SUSE Labs