linux-kernel - Re: [PATCH][v2] hung_task: Panic after fixed number of hung tasks

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <B0A75949-C40A-49E7-83BD-58D6BD5A1493@kernel.org>
Date: Fri, 10 Oct 2025 22:47:08 -0700
From: Kees Cook <kees@...nel.org>
To: Randy Dunlap <rdunlap@...radead.org>, lirongqing <lirongqing@...du.com>,
 corbet@....net, akpm@...ux-foundation.org, lance.yang@...ux.dev,
 mhiramat@...nel.org, paulmck@...nel.org, pawan.kumar.gupta@...ux.intel.com,
 mingo@...nel.org, dave.hansen@...ux.intel.com, rostedt@...dmis.org,
 arnd@...db.de, feng.tang@...ux.alibaba.com, pauld@...hat.com,
 joel.granados@...nel.org, linux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH][v2] hung_task: Panic after fixed number of hung tasks



On October 10, 2025 5:25:05 PM PDT, Randy Dunlap <rdunlap@...radead.org> wrote:
>Hi,
>
>On 9/27/25 10:31 PM, lirongqing wrote:
>> From: Li RongQing <lirongqing@...du.com>
>> 
>> Currently, when hung_task_panic is enabled, kernel will panic immediately
>> upon detecting the first hung task. However, some hung tasks are transient
>> and the system can recover fully, while others are unrecoverable and
>> trigger consecutive hung task reports, and a panic is expected.
>> 
>> This commit adds a new sysctl parameter hung_task_count_to_panic to allows
>> specifying the number of consecutive hung tasks that must be detected

Why make a new sysctl? Can't you just use hung_task_panic and raise the max to INT_MAX?

-Kees

>> before triggering a kernel panic. This provides finer control for
>> environments where transient hangs maybe happen but persistent hangs should
>> still be fatal.
>> 
>> Acked-by: Lance Yang <lance.yang@...ux.dev>
>> Signed-off-by: Li RongQing <lirongqing@...du.com>
>> ---
>> Diff with v1: change documentation as Lance suggested
>> 
>>  Documentation/admin-guide/sysctl/kernel.rst |  8 ++++++++
>>  kernel/hung_task.c                          | 14 +++++++++++++-
>>  2 files changed, 21 insertions(+), 1 deletion(-)
>> 
>> diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
>> index 8b49eab..98b47a7 100644
>> --- a/Documentation/admin-guide/sysctl/kernel.rst
>> +++ b/Documentation/admin-guide/sysctl/kernel.rst
>> @@ -405,6 +405,14 @@ This file shows up if ``CONFIG_DETECT_HUNG_TASK`` is enabled.
>>  1 Panic immediately.
>>  = =================================================
>>  
>> +hung_task_count_to_panic
>> +=====================
>
>The underline length should be at least as long as the title to
>prevent kernel-doc build warnings. Same length is preferred.
>
>> +
>> +When set to a non-zero value, a kernel panic will be triggered if the
>> +number of detected hung tasks reaches this value.
>> +
>> +Note that setting hung_task_panic=1 will still cause an immediate panic
>> +on the first hung task.
>>  
>>  hung_task_check_count
>>  =====================
>

-- 
Kees Cook