Commit d7477559 authored by Feng Tang's avatar Feng Tang Committed by Andrew Morton
Browse files

panic: add 'panic_sys_info' sysctl to take human readable string parameter 

Bitmap definition for 'panic_print' is hard to remember and decode.  Add
'panic_sys_info='sysctl to take human readable string like
"tasks,mem,timers,locks,ftrace,..." and translate it into bitmap.

The detailed mapping is:
	SYS_INFO_TASKS		"tasks"
	SYS_INFO_MEM		"mem"
	SYS_INFO_TIMERS		"timers"
	SYS_INFO_LOCKS		"locks"
	SYS_INFO_FTRACE		"ftrace"
	SYS_INFO_ALL_CPU_BT	"all_bt"
	SYS_INFO_BLOCKED_TASKS	"blocked_tasks"

[nathan@kernel.org: add __maybe_unused to sys_info_avail]
  Link: https://lkml.kernel.org/r/20250708-fix-clang-sys_info_avail-warning-v1-1-60d239eacd64@kernel.org
Link: https://lkml.kernel.org/r/20250703021004.42328-4-feng.tang@linux.alibaba.com


Signed-off-by: default avatarFeng Tang <feng.tang@linux.alibaba.com>
Suggested-by: default avatarPetr Mladek <pmladek@suse.com>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: "Paul E . McKenney" <paulmck@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent b76e89e5

Documentation/admin-guide/sysctl/kernel.rst

+18 −0
Original line number Diff line number Diff line
@@ -899,6 +899,24 @@ So for example to print tasks and memory info on panic, user can:: 
  echo 3 > /proc/sys/kernel/panic_print





panic_sys_info

==============



A comma separated list of extra information to be dumped on panic,

for example, "tasks,mem,timers,...".  It is a human readable alternative

to 'panic_print'. Possible values are:



=============   ===================================================

tasks           print all tasks info

mem             print system memory info

timer           print timers info

lock            print locks info if CONFIG_LOCKDEP is on

ftrace          print ftrace buffer

all_bt          print all CPUs backtrace (if available in the arch)

blocked_tasks   print only tasks in uninterruptible (blocked) state

=============   ===================================================





panic_on_rcu_stall

==================

include/linux/sys_info.h

+8 −0
Original line number Diff line number Diff line
@@ -2,6 +2,8 @@ 
#ifndef _LINUX_SYS_INFO_H

#define _LINUX_SYS_INFO_H



#include <linux/sysctl.h>



/*

 * SYS_INFO_PANIC_CONSOLE_REPLAY is for panic case only, as it needs special

 * handling which only fits panic case.
@@ -16,5 +18,11 @@ 
#define SYS_INFO_BLOCKED_TASKS		0x00000080



void sys_info(unsigned long si_mask);

unsigned long sys_info_parse_param(char *str);



#ifdef CONFIG_SYSCTL

int sysctl_sys_info_handler(const struct ctl_table *ro_table, int write,

					  void *buffer, size_t *lenp,

					  loff_t *ppos);

#endif

#endif	/* _LINUX_SYS_INFO_H */

kernel/panic.c

+7 −0
Original line number Diff line number Diff line
@@ -126,6 +126,13 @@ static const struct ctl_table kern_panic_table[] = { 
		.mode           = 0644,

		.proc_handler   = proc_douintvec,

	},

	{

		.procname	= "panic_sys_info",

		.data		= &panic_print,

		.maxlen         = sizeof(panic_print),

		.mode		= 0644,

		.proc_handler	= sysctl_sys_info_handler,

	},

};



static __init int kernel_panic_sysctls_init(void)

lib/sys_info.c

+90 −0
Original line number Diff line number Diff line
@@ -3,10 +3,100 @@ 
#include <linux/console.h>

#include <linux/kernel.h>

#include <linux/ftrace.h>

#include <linux/sysctl.h>

#include <linux/nmi.h>



#include <linux/sys_info.h>



struct sys_info_name {

	unsigned long bit;

	const char *name;

};



/*

 * When 'si_names' gets updated,  please make sure the 'sys_info_avail'

 * below is updated accordingly.

 */

static const struct sys_info_name  si_names[] = {

	{ SYS_INFO_TASKS,		"tasks" },

	{ SYS_INFO_MEM,			"mem" },

	{ SYS_INFO_TIMERS,		"timers" },

	{ SYS_INFO_LOCKS,		"locks" },

	{ SYS_INFO_FTRACE,		"ftrace" },

	{ SYS_INFO_ALL_CPU_BT,		"all_bt" },

	{ SYS_INFO_BLOCKED_TASKS,	"blocked_tasks" },

};



/* Expecting string like "xxx_sys_info=tasks,mem,timers,locks,ftrace,..." */

unsigned long sys_info_parse_param(char *str)

{

	unsigned long si_bits = 0;

	char *s, *name;

	int i;



	s = str;

	while ((name = strsep(&s, ",")) && *name) {

		for (i = 0; i < ARRAY_SIZE(si_names); i++) {

			if (!strcmp(name, si_names[i].name)) {

				si_bits |= si_names[i].bit;

				break;

			}

		}

	}



	return si_bits;

}



#ifdef CONFIG_SYSCTL



static const char sys_info_avail[] __maybe_unused = "tasks,mem,timers,locks,ftrace,all_bt,blocked_tasks";



int sysctl_sys_info_handler(const struct ctl_table *ro_table, int write,

					  void *buffer, size_t *lenp,

					  loff_t *ppos)

{

	char names[sizeof(sys_info_avail) + 1];

	struct ctl_table table;

	unsigned long *si_bits_global;



	si_bits_global = ro_table->data;



	if (write) {

		unsigned long si_bits;

		int ret;



		table = *ro_table;

		table.data = names;

		table.maxlen = sizeof(names);

		ret = proc_dostring(&table, write, buffer, lenp, ppos);

		if (ret)

			return ret;



		si_bits = sys_info_parse_param(names);

		/* The access to the global value is not synchronized. */

		WRITE_ONCE(*si_bits_global, si_bits);

		return 0;

	} else {

		/* for 'read' operation */

		char *delim = "";

		int i, len = 0;



		for (i = 0; i < ARRAY_SIZE(si_names); i++) {

			if (*si_bits_global & si_names[i].bit) {

				len += scnprintf(names + len, sizeof(names) - len,

					"%s%s", delim, si_names[i].name);

				delim = ",";

			}

		}



		table = *ro_table;

		table.data = names;

		table.maxlen = sizeof(names);

		return proc_dostring(&table, write, buffer, lenp, ppos);

	}

}

#endif



void sys_info(unsigned long si_mask)

{

	if (si_mask & SYS_INFO_TASKS)