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

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

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 <>
Reviewed-by: default avatarRik van Riel <>
Acked-by: default avatarDavid Rientjes <>
[ Build warning fix. ]
Signed-off-by: default avatarIngo Molnar <>
parent 2397efb1
......@@ -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".
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.
The upper bound on the number of tasks that are checked.
This file shows up if CONFIG_DETECT_HUNG_TASK is enabled.
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.
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.
This toggle indicates whether restrictions are placed on
......@@ -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);
......@@ -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;
......@@ -98,7 +98,9 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout)
if (!sysctl_hung_task_warnings)
if (sysctl_hung_task_warnings > 0)
* Ok, the task did not get scheduled for more than 2 minutes,
......@@ -122,7 +122,8 @@ extern int blk_iopoll_enabled;
static int sixty = 60;
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,
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