Message-ID: <0b5934aa-7788-480c-93f8-2906396f44fe@linux.dev>
Date: Thu, 3 Jul 2025 12:56:54 +0800
From: Lance Yang <lance.yang@...ux.dev>
To: Feng Tang <feng.tang@...ux.alibaba.com>
Cc: paulmck@...nel.org, john.ogness@...utronix.de,
 Andrew Morton <akpm@...ux-foundation.org>,
 Steven Rostedt <rostedt@...dmis.org>, Petr Mladek <pmladek@...e.com>,
 Jonathan Corbet <corbet@....net>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/5] generalize panic_print's dump function to be used
 by other kernel parts



On 2025/7/3 11:23, Lance Yang wrote:
> Just hit a build failure with this patch series when building for arm64
> with a minimal configuration:
> 
> kernel/panic.c: In function ‘setup_panic_sys_info’:
> kernel/panic.c:151:23: error: implicit declaration of function 
> ‘sys_info_parse_param’ [-Wimplicit-function-declaration]
> 151 |         panic_print = sys_info_parse_param(buf);
> |                       ^~~~~~~~~~~~~~~~~~~~
> make[3]: *** [scripts/Makefile.build:287: kernel/panic.o] Error 1
> make[2]: *** [scripts/Makefile.build:554: kernel] Error 2
> 
> 
> To reproduce it:
> $ make ARCH=arm64 allnoconfig
> $ make ARCH=arm64 -j$(nproc)

Realized that now: the root cause of the build failure I saw is the
missing "v3" tag in the subject of the patch #03 - sorry!

b4 reported that it couldn't find patch #03 when I tried to apply
this patch series, which is why I was getting the "implicit function
declaration" error ... Obviously, I missed that error before ;(

```
---
   ✓ [PATCH v3 1/5] panic: clean up code for console replay
     ✓ Signed: DKIM/linux.alibaba.com
   ✓ [PATCH v3 2/5] panic: generalize panic_print's function to show sys 
info
     ✓ Signed: DKIM/linux.alibaba.com
   ERROR: missing [3/5]!
   ✓ [PATCH v3 4/5] panic: add 'panic_sys_info=' setup option for kernel 
cmdline
     ✓ Signed: DKIM/linux.alibaba.com
   ✓ [PATCH v3 5/5] panic: add note that panic_print sysctl interface is 
deprecated
     ✓ Signed: DKIM/linux.alibaba.com
---
Total patches: 4
---
WARNING: Thread incomplete!
Applying: panic: clean up code for console replay
Applying: panic: generalize panic_print's function to show sys info
Applying: panic: add 'panic_sys_info=' setup option for kernel cmdline
Applying: panic: add note that panic_print sysctl interface is deprecated
```

Thanks,
Lance

> 
> Thanks,
> Lance
> 
> 
> On 2025/7/3 10:09, Feng Tang wrote:
>> When working on kernel stability issues, panic, task-hung and
>> software/hardware lockup are frequently met. And to debug them, user
>> may need lots of system information at that time, like task call stacks,
>> lock info, memory info etc.
>>
>> panic case already has panic_print_sys_info() for this purpose, and has
>> a 'panic_print' bitmask to control what kinds of information is needed,
>> which is also helpful to debug other task-hung and lockup cases.
>>
>> So this patchset extract the function out to a new file 'lib/sys_info.c',
>> and make it available for other cases which also need to dump system info
>> for debugging.
>>
>> Also as suggested by Petr Mladek, add 'panic_sys_info=' interface to
>> take human readable string like "tasks,mem,locks,timers,ftrace,....",
>> and eventually obsolete the current 'panic_print' bitmap interface.
>>
>> In RFC and V1 version, hung_task and SW/HW watchdog modules are enabled
>> with the new sys_info dump interface. In v2, they are kept out for
>> better review of current change, and will be posted later.
>>
>> Locally these have been used in our bug chasing for stability issues
>> and was proven helpful.
>>
>> Many thanks to Petr Mladek for great suggestions on both the code and
>> architectures!
>>
>> - Feng
>>
>> One to do left is about adding note for obsoleting 'panic_print' cmdline
>> as discussed in https://lore.kernel.org/lkml/ 
>> aFvBuOnD0cAEWJfl@...FWC9VHC-2323.local/
>> and will be posted later.
>>
>> Changelog:
>>
>>    Since v2:
>>       * Rename to PANIC_CONSOLE_REPLAY (Petr Mladek)
>>       * Don't let kernel.h include sys_info.h (Petr Mladek)
>>       * Improve documents and coding style (Petr Mladek/Lance Yang)
>>       * Add 'panic_console_replay' parameter (Petr Mladek)
>>       * Fix compiling problem (0Day bot)
>>       * Add reviewed-by tag from Petr for patch 1/5
>>
>>    Since V1:
>>       * Separate the 'sys_show_info' related code to new file 
>> sys_info.[ch]
>>         (Petr Mladek)
>>       * Clean up the code for panic console replay (Petr Mladek)
>>       * Add 'panic_sys_info=' cmdline and sysctl interface for taking
>>         human readable parameters (Petr Mladek)
>>       * Add note about the obsoleting of 'panic_print' (Petr Mladek)
>>       * Hold the changes to hungtask/watchdog
>>
>>    Since RFC:
>>       * Don't print all cpu backtrace if 
>> 'sysctl_hung_task_all_cpu_backtracemay'
>>         is 'false' (Lance Yang)
>>       * Change the name of 2 new kernel control knob to have 'mask' 
>> inside, and
>>         add kernel document and code comments for them (Lance Yang)
>>       * Make the sys_show_info() support printk msg replay and all CPU 
>> backtrace.
>>
>> Feng Tang (5):
>>    panic: clean up code for console replay
>>    panic: generalize panic_print's function to show sys info
>>    panic: add 'panic_sys_info' sysctl to take human readable string
>>      parameter
>>    panic: add 'panic_sys_info=' setup option for kernel cmdline
>>    panic: add note that panic_print sysctl interface is deprecated
>>
>>   .../admin-guide/kernel-parameters.txt         |  21 ++-
>>   Documentation/admin-guide/sysctl/kernel.rst   |  20 ++-
>>   include/linux/sys_info.h                      |  27 ++++
>>   kernel/panic.c                                |  71 +++++-----
>>   lib/Makefile                                  |   2 +-
>>   lib/sys_info.c                                | 122 ++++++++++++++++++
>>   6 files changed, 221 insertions(+), 42 deletions(-)
>>   create mode 100644 include/linux/sys_info.h
>>   create mode 100644 lib/sys_info.c
>>
> 

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