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Commit 270750db authored by Aaron Tomlin's avatar Aaron Tomlin Committed by Ingo Molnar
Browse files

hung_task: Display every hung task warning 



When khungtaskd detects hung tasks, it prints out
backtraces from a number of those tasks.

Limiting the number of backtraces being printed
out can result in the user not seeing the information
necessary to debug the issue. The hung_task_warnings
sysctl controls this feature.

This patch makes it possible for hung_task_warnings
to accept a special value to print an unlimited
number of backtraces when khungtaskd detects hung
tasks.

The special value is -1. To use this value it is
necessary to change types from ulong to int.

Signed-off-by: default avatarAaron Tomlin <atomlin@redhat.com>
Reviewed-by: default avatarRik van Riel <riel@redhat.com>
Acked-by: default avatarDavid Rientjes <rientjes@google.com>
Cc: oleg@redhat.com
Link: http://lkml.kernel.org/r/1390239253-24030-3-git-send-email-atomlin@redhat.com


[ Build warning fix. ]
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 2397efb1

Documentation/sysctl/kernel.txt

+42 −0
Original line number Diff line number Diff line
@@ -33,6 +33,10 @@ show up in /proc/sys/kernel: 
- domainname

- hostname

- hotplug

- hung_task_panic

- hung_task_check_count

- hung_task_timeout_secs

- hung_task_warnings

- kptr_restrict

- kstack_depth_to_print       [ X86 only ]

- l2cr                        [ PPC only ]
@@ -287,6 +291,44 @@ Default value is "/sbin/hotplug". 


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



hung_task_panic:



Controls the kernel's behavior when a hung task is detected.

This file shows up if CONFIG_DETECT_HUNG_TASK is enabled.



0: continue operation. This is the default behavior.



1: panic immediately.



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



hung_task_check_count:



The upper bound on the number of tasks that are checked.

This file shows up if CONFIG_DETECT_HUNG_TASK is enabled.



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



hung_task_timeout_secs:



Check interval. When a task in D state did not get scheduled

for more than this value report a warning.

This file shows up if CONFIG_DETECT_HUNG_TASK is enabled.



0: means infinite timeout - no checking done.



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



hung_task_warning:



The maximum number of warnings to report. During a check interval

When this value is reached, no more the warnings will be reported.

This file shows up if CONFIG_DETECT_HUNG_TASK is enabled.



-1: report an infinite number of warnings.



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



kptr_restrict:



This toggle indicates whether restrictions are placed on

include/linux/sched/sysctl.h

+1 −1
Original line number Diff line number Diff line
@@ -5,7 +5,7 @@ 
extern int	     sysctl_hung_task_check_count;

extern unsigned int  sysctl_hung_task_panic;

extern unsigned long sysctl_hung_task_timeout_secs;

extern unsigned long sysctl_hung_task_warnings;

extern int sysctl_hung_task_warnings;

extern int proc_dohung_task_timeout_secs(struct ctl_table *table, int write,

					 void __user *buffer,

					 size_t *lenp, loff_t *ppos);

kernel/hung_task.c

+4 −2
Original line number Diff line number Diff line
@@ -37,7 +37,7 @@ int __read_mostly sysctl_hung_task_check_count = PID_MAX_LIMIT; 
 */

unsigned long __read_mostly sysctl_hung_task_timeout_secs = CONFIG_DEFAULT_HUNG_TASK_TIMEOUT;



unsigned long __read_mostly sysctl_hung_task_warnings = 10;

int __read_mostly sysctl_hung_task_warnings = 10;



static int __read_mostly did_panic;
@@ -98,6 +98,8 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout) 


	if (!sysctl_hung_task_warnings)

		return;



	if (sysctl_hung_task_warnings > 0)

		sysctl_hung_task_warnings--;



	/*

kernel/sysctl.c

+5 −3
Original line number Diff line number Diff line
@@ -122,7 +122,8 @@ extern int blk_iopoll_enabled; 
static int sixty = 60;

#endif



static int neg_one = -1;

static int __maybe_unused neg_one = -1;



static int zero;

static int __maybe_unused one = 1;

static int __maybe_unused two = 2;
@@ -978,9 +979,10 @@ static struct ctl_table kern_table[] = { 
	{

		.procname	= "hung_task_warnings",

		.data		= &sysctl_hung_task_warnings,

		.maxlen		= sizeof(unsigned long),

		.maxlen		= sizeof(int),

		.mode		= 0644,

		.proc_handler	= proc_doulongvec_minmax,

		.proc_handler	= proc_dointvec_minmax,

		.extra1		= &neg_one,

	},

#endif

#ifdef CONFIG_COMPAT