Commit 8b2b9b4f authored by Feng Tang's avatar Feng Tang Committed by Andrew Morton
Browse files

hung_task: add hung_task_sys_info sysctl to dump sys info on task-hung 

When task-hung happens, developers may need different kinds of system
information (call-stacks, memory info, locks, etc.) to help debugging.

Add 'hung_task_sys_info' sysctl knob to take human readable string like
"tasks,mem,timers,locks,ftrace,...", and when task-hung happens, all
requested information will be dumped.  (refer kernel/sys_info.c for more
details).

Meanwhile, the newly introduced sys_info() call is used to unify some
existing info-dumping knobs.

[feng.tang@linux.alibaba.com: maintain consistecy established behavior, per Lance and Petr]
  Link: https://lkml.kernel.org/r/aRncJo1mA5Zk77Hr@U-2FWC9VHC-2323.local
Link: https://lkml.kernel.org/r/20251113111039.22701-3-feng.tang@linux.alibaba.com


Signed-off-by: default avatarFeng Tang <feng.tang@linux.alibaba.com>
Suggested-by: default avatarPetr Mladek <pmladek@suse.com>
Reviewed-by: default avatarPetr Mladek <pmladek@suse.com>
Reviewed-by: default avatarLance Yang <lance.yang@linux.dev>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: "Paul E . McKenney" <paulmck@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 5f264c00

Documentation/admin-guide/sysctl/kernel.rst

+5 −0
Original line number Diff line number Diff line
@@ -422,6 +422,11 @@ the system boot. 


This file shows up if ``CONFIG_DETECT_HUNG_TASK`` is enabled.



hung_task_sys_info

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

A comma separated list of extra system information to be dumped when

hung task is detected, for example, "tasks,mem,timers,locks,...".

Refer 'panic_sys_info' section below for more details.



hung_task_timeout_secs

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

kernel/hung_task.c

+28 −12
Original line number Diff line number Diff line
@@ -24,6 +24,7 @@ 
#include <linux/sched/sysctl.h>

#include <linux/hung_task.h>

#include <linux/rwsem.h>

#include <linux/sys_info.h>



#include <trace/events/sched.h>
@@ -59,12 +60,17 @@ static unsigned long __read_mostly sysctl_hung_task_check_interval_secs; 
static int __read_mostly sysctl_hung_task_warnings = 10;



static int __read_mostly did_panic;

static bool hung_task_show_lock;

static bool hung_task_call_panic;

static bool hung_task_show_all_bt;



static struct task_struct *watchdog_task;



/*

 * A bitmask to control what kinds of system info to be printed when

 * a hung task is detected, it could be task, memory, lock etc. Refer

 * include/linux/sys_info.h for detailed bit definition.

 */

static unsigned long hung_task_si_mask;



#ifdef CONFIG_SMP

/*

 * Should we dump all CPUs backtraces in a hung task event?
@@ -236,7 +242,6 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout, 


	if (sysctl_hung_task_panic && total_hung_task >= sysctl_hung_task_panic) {

		console_verbose();

		hung_task_show_lock = true;

		hung_task_call_panic = true;

	}
@@ -259,10 +264,7 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout, 
			" disables this message.\n");

		sched_show_task(t);

		debug_show_blocker(t, timeout);

		hung_task_show_lock = true;



		if (sysctl_hung_task_all_cpu_backtrace)

			hung_task_show_all_bt = true;

		if (!sysctl_hung_task_warnings)

			pr_info("Future hung task reports are suppressed, see sysctl kernel.hung_task_warnings\n");

	}
@@ -304,6 +306,8 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout) 
	unsigned long last_break = jiffies;

	struct task_struct *g, *t;

	unsigned long prev_detect_count = sysctl_hung_task_detect_count;

	int need_warning = sysctl_hung_task_warnings;

	unsigned long si_mask = hung_task_si_mask;



	/*

	 * If the system crashed already then all bets are off,
@@ -312,7 +316,7 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout) 
	if (test_taint(TAINT_DIE) || did_panic)

		return;



	hung_task_show_lock = false;



	rcu_read_lock();

	for_each_process_thread(g, t) {
@@ -328,14 +332,19 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout) 
	}

 unlock:

	rcu_read_unlock();

	if (hung_task_show_lock)

		debug_show_all_locks();



	if (hung_task_show_all_bt) {

		hung_task_show_all_bt = false;

		trigger_all_cpu_backtrace();

	if (!(sysctl_hung_task_detect_count - prev_detect_count))

		return;



	if (need_warning || hung_task_call_panic) {

		si_mask |= SYS_INFO_LOCKS;



		if (sysctl_hung_task_all_cpu_backtrace)

			si_mask |= SYS_INFO_ALL_BT;

	}



	sys_info(si_mask);



	if (hung_task_call_panic)

		panic("hung_task: blocked tasks");

}
@@ -434,6 +443,13 @@ static const struct ctl_table hung_task_sysctls[] = { 
		.mode		= 0444,

		.proc_handler	= proc_doulongvec_minmax,

	},

	{

		.procname	= "hung_task_sys_info",

		.data		= &hung_task_si_mask,

		.maxlen         = sizeof(hung_task_si_mask),

		.mode		= 0644,

		.proc_handler	= sysctl_sys_info_handler,

	},

};



static void __init hung_task_sysctl_init(void)