From: Feng Tang Date: Thu, 3 Jul 2025 02:10:00 +0000 (+0800) Subject: panic: clean up code for console replay X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=261743b0135d1d578cab407ba0cf226df30b43d8;p=thirdparty%2Flinux.git panic: clean up code for console replay Patch series "generalize panic_print's dump function to be used by other kernel parts", v3. 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 extracts the function out to a new file 'lib/sys_info.c', and makes 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! This patch (of 5): Currently the panic_print_sys_info() was called twice with different parameters to handle console replay case, which is kind of confusing. Add panic_console_replay() explicitly and rename 'PANIC_PRINT_ALL_PRINTK_MSG' to 'PANIC_CONSOLE_REPLAY', to make the code straightforward. The related kernel document is also updated. Link: https://lkml.kernel.org/r/20250703021004.42328-1-feng.tang@linux.alibaba.com Link: https://lkml.kernel.org/r/20250703021004.42328-2-feng.tang@linux.alibaba.com Signed-off-by: Feng Tang Suggested-by: Petr Mladek Reviewed-by: Petr Mladek Cc: John Ogness Cc: Jonathan Corbet Cc: Lance Yang Cc: "Paul E . McKenney" Cc: Steven Rostedt Cc: Nathan Chancellor Signed-off-by: Andrew Morton --- diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index ac4a239b9388c..3780b7e6bfd5a 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -4555,7 +4555,7 @@ bit 2: print timer info bit 3: print locks info if CONFIG_LOCKDEP is on bit 4: print ftrace buffer - bit 5: print all printk messages in buffer + bit 5: replay all messages on consoles at the end of panic bit 6: print all CPUs backtrace (if available in the arch) bit 7: print only tasks in uninterruptible (blocked) state *Be aware* that this option may print a _lot_ of lines, diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst index dd49a89a62d35..0d08b7a2db2da 100644 --- a/Documentation/admin-guide/sysctl/kernel.rst +++ b/Documentation/admin-guide/sysctl/kernel.rst @@ -889,7 +889,7 @@ bit 1 print system memory info bit 2 print timer info bit 3 print locks info if ``CONFIG_LOCKDEP`` is on bit 4 print ftrace buffer -bit 5 print all printk messages in buffer +bit 5 replay all messages on consoles at the end of panic bit 6 print all CPUs backtrace (if available in the arch) bit 7 print only tasks in uninterruptible (blocked) state ===== ============================================ diff --git a/kernel/panic.c b/kernel/panic.c index b0b9a8bf4560d..9b6c5dc28a653 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -74,7 +74,7 @@ EXPORT_SYMBOL_GPL(panic_timeout); #define PANIC_PRINT_TIMER_INFO 0x00000004 #define PANIC_PRINT_LOCK_INFO 0x00000008 #define PANIC_PRINT_FTRACE_INFO 0x00000010 -#define PANIC_PRINT_ALL_PRINTK_MSG 0x00000020 +#define PANIC_CONSOLE_REPLAY 0x00000020 #define PANIC_PRINT_ALL_CPU_BT 0x00000040 #define PANIC_PRINT_BLOCKED_TASKS 0x00000080 unsigned long panic_print; @@ -238,14 +238,14 @@ void nmi_panic(struct pt_regs *regs, const char *msg) } EXPORT_SYMBOL(nmi_panic); -static void panic_print_sys_info(bool console_flush) +static void panic_console_replay(void) { - if (console_flush) { - if (panic_print & PANIC_PRINT_ALL_PRINTK_MSG) - console_flush_on_panic(CONSOLE_REPLAY_ALL); - return; - } + if (panic_print & PANIC_CONSOLE_REPLAY) + console_flush_on_panic(CONSOLE_REPLAY_ALL); +} +static void panic_print_sys_info(void) +{ if (panic_print & PANIC_PRINT_TASK_INFO) show_state(); @@ -410,7 +410,7 @@ void panic(const char *fmt, ...) */ atomic_notifier_call_chain(&panic_notifier_list, 0, buf); - panic_print_sys_info(false); + panic_print_sys_info(); kmsg_dump_desc(KMSG_DUMP_PANIC, buf); @@ -439,7 +439,7 @@ void panic(const char *fmt, ...) debug_locks_off(); console_flush_on_panic(CONSOLE_FLUSH_PENDING); - panic_print_sys_info(true); + panic_console_replay(); if (!panic_blink) panic_blink = no_blink;