linux-kernel - Re: [PATCH v3 0/5] generalize panic_print's dump function to be used by other kernel parts

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Message-ID: <5f4f048e-02ff-4669-b4b1-e411c6be536b@linux.dev>
Date: Thu, 3 Jul 2025 11:23:32 +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

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)

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@U-2FWC9VHC-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
>