[PATCH v2] hung_task : check the value of "sysctl_hung_task_timeout_sec"

[PATCH v2] hung_task : check the value of "sysctl_hung_task_timeout_sec"

[Liu Hua]

As sysctl_hung_task_timeout_sec is unsigned long, when this value is
larger then LONG_MAX/HZ, the function schedule_timeout_interruptible in
watchdog will return immediately without sleep and with print :

[  205.452934] schedule_timeout: wrong timeout value ffffffffffffff83

and then the funtion watchdog will call schedule_timeout_interruptible again
and again. The screen will be filled with
	"schedule_timeout: wrong timeout value ffffffffffffff83"

This patch does some check and correction in timeout_jiffies, to let the
function schedule_timeout_interruptible allways get the valid parameter.

Cc: <stable@vger.kernel.org>
Signed-off-by: Liu Hua <sdu.liu@huawei.com>
---
 kernel/hung_task.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/kernel/hung_task.c b/kernel/hung_task.c
index 6df6149..f992286 100644
--- a/kernel/hung_task.c
+++ b/kernel/hung_task.c
@@ -174,8 +174,12 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
 
 static unsigned long timeout_jiffies(unsigned long timeout)
 {
-	/* timeout of 0 will disable the watchdog */
-	return timeout ? timeout * HZ : MAX_SCHEDULE_TIMEOUT;
+	/* timeout of 0 or >= LONG_MAX/HZ will disable the watchdog */
+	if ((timeout == 0) || (timeout > MAX_SCHEDULE_TIMEOUT))
+		return MAX_SCHEDULE_TIMEOUT;
+
+	return (timeout * HZ) < MAX_SCHEDULE_TIMEOUT ?
+			timeout * HZ : MAX_SCHEDULE_TIMEOUT;
 }
 
 /*
-- 
1.9.0

Re: [PATCH v2] hung_task : check the value of "sysctl_hung_task_timeout_sec"

[Satoru Takeuchi]

At Sun, 23 Mar 2014 15:54:04 +0800,
Liu Hua wrote:
> 
> As sysctl_hung_task_timeout_sec is unsigned long, when this value is
> larger then LONG_MAX/HZ, the function schedule_timeout_interruptible in
> watchdog will return immediately without sleep and with print :
> 
> [  205.452934] schedule_timeout: wrong timeout value ffffffffffffff83
> 
> and then the funtion watchdog will call schedule_timeout_interruptible again
> and again. The screen will be filled with
> 	"schedule_timeout: wrong timeout value ffffffffffffff83"
> 
> This patch does some check and correction in timeout_jiffies, to let the
> function schedule_timeout_interruptible allways get the valid parameter.
> 
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Liu Hua <sdu.liu@huawei.com>
> ---
>  kernel/hung_task.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/hung_task.c b/kernel/hung_task.c
> index 6df6149..f992286 100644
> --- a/kernel/hung_task.c
> +++ b/kernel/hung_task.c
> @@ -174,8 +174,12 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
>  
>  static unsigned long timeout_jiffies(unsigned long timeout)
>  {
> -	/* timeout of 0 will disable the watchdog */
> -	return timeout ? timeout * HZ : MAX_SCHEDULE_TIMEOUT;
> +	/* timeout of 0 or >= LONG_MAX/HZ will disable the watchdog */
> +	if ((timeout == 0) || (timeout > MAX_SCHEDULE_TIMEOUT))

You should check whether sysctl_hung_task_timeout_sec > MAX_SCHEDULE_TIMEOUT/HZ
or not when setting this parameter instead. Then this check ins't necessary here.

# Just FYI, MAX_SCHEDULE_TIMEOUT should be MAX_SCHEDULE_TIMEOUT/HZ here. 

Thanks,
Satoru

> +		return MAX_SCHEDULE_TIMEOUT;
> +
> +	return (timeout * HZ) < MAX_SCHEDULE_TIMEOUT ?
> +			timeout * HZ : MAX_SCHEDULE_TIMEOUT;
>  }
>  
>  /*
> -- 
> 1.9.0
> 
> --
> To unsubscribe from this list: send the line "unsubscribe stable" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH v2] hung_task : check the value of "sysctl_hung_task_timeout_sec"

[Liu hua]

于 2014/3/24 4:50, Satoru Takeuchi 写道:
> At Sun, 23 Mar 2014 15:54:04 +0800,
> Liu Hua wrote:
>>
>> As sysctl_hung_task_timeout_sec is unsigned long, when this value is
>> larger then LONG_MAX/HZ, the function schedule_timeout_interruptible in
>> watchdog will return immediately without sleep and with print :
>>
>> [  205.452934] schedule_timeout: wrong timeout value ffffffffffffff83
>>
>> and then the funtion watchdog will call schedule_timeout_interruptible again
>> and again. The screen will be filled with
>> 	"schedule_timeout: wrong timeout value ffffffffffffff83"
>>
>> This patch does some check and correction in timeout_jiffies, to let the
>> function schedule_timeout_interruptible allways get the valid parameter.
>>
>> Cc: <stable@vger.kernel.org>
>> Signed-off-by: Liu Hua <sdu.liu@huawei.com>
>> ---
>>  kernel/hung_task.c | 8 ++++++--
>>  1 file changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/kernel/hung_task.c b/kernel/hung_task.c
>> index 6df6149..f992286 100644
>> --- a/kernel/hung_task.c
>> +++ b/kernel/hung_task.c
>> @@ -174,8 +174,12 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
>>  
>>  static unsigned long timeout_jiffies(unsigned long timeout)
>>  {
>> -	/* timeout of 0 will disable the watchdog */
>> -	return timeout ? timeout * HZ : MAX_SCHEDULE_TIMEOUT;
>> +	/* timeout of 0 or >= LONG_MAX/HZ will disable the watchdog */
>> +	if ((timeout == 0) || (timeout > MAX_SCHEDULE_TIMEOUT))
> 
> You should check whether sysctl_hung_task_timeout_sec > MAX_SCHEDULE_TIMEOUT/HZ
> or not when setting this parameter instead. Then this check ins't necessary here.
> 
> # Just FYI, MAX_SCHEDULE_TIMEOUT should be MAX_SCHEDULE_TIMEOUT/HZ here. 
> 
> Thanks,
> Satoru

 Yes, how about this :

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 49e13e1..aae21e8 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -144,6 +144,11 @@ static int min_percpu_pagelist_fract = 8;
 static int ngroups_max = NGROUPS_MAX;
 static const int cap_last_cap = CAP_LAST_CAP;

+/*this is needed for proc_doulongvec_minmax of sysctl_hung_task_timeout_secs */
+#ifdef CONFIG_DETECT_HUNG_TASK
+static unsigned long hung_task_timeout_max = (LONG_MAX/HZ);
+#endif
+
 #ifdef CONFIG_INOTIFY_USER
 #include <linux/inotify.h>
 #endif
@@ -995,6 +1000,7 @@ static struct ctl_table kern_table[] = {
 		.maxlen		= sizeof(unsigned long),
 		.mode		= 0644,
 		.proc_handler	= proc_dohung_task_timeout_secs,
+		.extra2		= &hung_task_timeout_max,
 	},
 	{
 		.procname	= "hung_task_warnings",
-- 
1.9.0

Thanks
Liu Hua



> 
>> +		return MAX_SCHEDULE_TIMEOUT;
>> +
>> +	return (timeout * HZ) < MAX_SCHEDULE_TIMEOUT ?
>> +			timeout * HZ : MAX_SCHEDULE_TIMEOUT;
>>  }
>>  
>>  /*
>> -- 
>> 1.9.0
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe stable" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 
> .
> 

Re: [PATCH v2] hung_task : check the value of "sysctl_hung_task_timeout_sec"

[Satoru Takeuchi]

At Tue, 25 Mar 2014 16:58:58 +0800,
Liu hua wrote:
> 
> 于 2014/3/24 4:50, Satoru Takeuchi 写道:
> > At Sun, 23 Mar 2014 15:54:04 +0800,
> > Liu Hua wrote:
> >>
> >> As sysctl_hung_task_timeout_sec is unsigned long, when this value is
> >> larger then LONG_MAX/HZ, the function schedule_timeout_interruptible in
> >> watchdog will return immediately without sleep and with print :
> >>
> >> [  205.452934] schedule_timeout: wrong timeout value ffffffffffffff83
> >>
> >> and then the funtion watchdog will call schedule_timeout_interruptible again
> >> and again. The screen will be filled with
> >> 	"schedule_timeout: wrong timeout value ffffffffffffff83"
> >>
> >> This patch does some check and correction in timeout_jiffies, to let the
> >> function schedule_timeout_interruptible allways get the valid parameter.
> >>
> >> Cc: <stable@vger.kernel.org>
> >> Signed-off-by: Liu Hua <sdu.liu@huawei.com>
> >> ---
> >>  kernel/hung_task.c | 8 ++++++--
> >>  1 file changed, 6 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/kernel/hung_task.c b/kernel/hung_task.c
> >> index 6df6149..f992286 100644
> >> --- a/kernel/hung_task.c
> >> +++ b/kernel/hung_task.c
> >> @@ -174,8 +174,12 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
> >>  
> >>  static unsigned long timeout_jiffies(unsigned long timeout)
> >>  {
> >> -	/* timeout of 0 will disable the watchdog */
> >> -	return timeout ? timeout * HZ : MAX_SCHEDULE_TIMEOUT;
> >> +	/* timeout of 0 or >= LONG_MAX/HZ will disable the watchdog */
> >> +	if ((timeout == 0) || (timeout > MAX_SCHEDULE_TIMEOUT))
> > 
> > You should check whether sysctl_hung_task_timeout_sec > MAX_SCHEDULE_TIMEOUT/HZ
> > or not when setting this parameter instead. Then this check ins't necessary here.
> > 
> > # Just FYI, MAX_SCHEDULE_TIMEOUT should be MAX_SCHEDULE_TIMEOUT/HZ here. 
> > 
> > Thanks,
> > Satoru
> 
>  Yes, how about this :

I confirmed the followings.

 - 3.14-rc8: system hunged up with "hung_task_timeout_secs > LONG_MAX/HZ".
 - 3.14-rc8 with your patch: works fine. I can't set the above mentioned value any more.

Writing possible values (0..LONG_MAX/HZ) in Documentation/sysctl/kernel.txt
make this patch better.

Thanks,
Satoru

> 
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 49e13e1..aae21e8 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -144,6 +144,11 @@ static int min_percpu_pagelist_fract = 8;
>  static int ngroups_max = NGROUPS_MAX;
>  static const int cap_last_cap = CAP_LAST_CAP;
> 
> +/*this is needed for proc_doulongvec_minmax of sysctl_hung_task_timeout_secs */
> +#ifdef CONFIG_DETECT_HUNG_TASK
> +static unsigned long hung_task_timeout_max = (LONG_MAX/HZ);
> +#endif
> +
>  #ifdef CONFIG_INOTIFY_USER
>  #include <linux/inotify.h>
>  #endif
> @@ -995,6 +1000,7 @@ static struct ctl_table kern_table[] = {
>  		.maxlen		= sizeof(unsigned long),
>  		.mode		= 0644,
>  		.proc_handler	= proc_dohung_task_timeout_secs,
> +		.extra2		= &hung_task_timeout_max,
>  	},
>  	{
>  		.procname	= "hung_task_warnings",
> -- 
> 1.9.0
> 
> Thanks
> Liu Hua
> 
> 
> 
> > 
> >> +		return MAX_SCHEDULE_TIMEOUT;
> >> +
> >> +	return (timeout * HZ) < MAX_SCHEDULE_TIMEOUT ?
> >> +			timeout * HZ : MAX_SCHEDULE_TIMEOUT;
> >>  }
> >>  
> >>  /*
> >> -- 
> >> 1.9.0
> >>
> >> --
> >> To unsubscribe from this list: send the line "unsubscribe stable" in
> >> the body of a message to majordomo@vger.kernel.org
> >> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > 
> > .
> > 
> 
> 

Re: [PATCH v2] hung_task : check the value of "sysctl_hung_task_timeout_sec"

[Liu hua]

于 2014/3/26 0:25, Satoru Takeuchi 写道:
> At Tue, 25 Mar 2014 16:58:58 +0800,
> Liu hua wrote:
>>
>> 于 2014/3/24 4:50, Satoru Takeuchi 写道:
>>> At Sun, 23 Mar 2014 15:54:04 +0800,
>>> Liu Hua wrote:
>>>>
>>>> As sysctl_hung_task_timeout_sec is unsigned long, when this value is
>>>> larger then LONG_MAX/HZ, the function schedule_timeout_interruptible in
>>>> watchdog will return immediately without sleep and with print :
>>>>
>>>> [  205.452934] schedule_timeout: wrong timeout value ffffffffffffff83
>>>>
>>>> and then the funtion watchdog will call schedule_timeout_interruptible again
>>>> and again. The screen will be filled with
>>>> 	"schedule_timeout: wrong timeout value ffffffffffffff83"
>>>>
>>>> This patch does some check and correction in timeout_jiffies, to let the
>>>> function schedule_timeout_interruptible allways get the valid parameter.
>>>>
>>>> Cc: <stable@vger.kernel.org>
>>>> Signed-off-by: Liu Hua <sdu.liu@huawei.com>
>>>> ---
>>>>  kernel/hung_task.c | 8 ++++++--
>>>>  1 file changed, 6 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/kernel/hung_task.c b/kernel/hung_task.c
>>>> index 6df6149..f992286 100644
>>>> --- a/kernel/hung_task.c
>>>> +++ b/kernel/hung_task.c
>>>> @@ -174,8 +174,12 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
>>>>  
>>>>  static unsigned long timeout_jiffies(unsigned long timeout)
>>>>  {
>>>> -	/* timeout of 0 will disable the watchdog */
>>>> -	return timeout ? timeout * HZ : MAX_SCHEDULE_TIMEOUT;
>>>> +	/* timeout of 0 or >= LONG_MAX/HZ will disable the watchdog */
>>>> +	if ((timeout == 0) || (timeout > MAX_SCHEDULE_TIMEOUT))
>>>
>>> You should check whether sysctl_hung_task_timeout_sec > MAX_SCHEDULE_TIMEOUT/HZ
>>> or not when setting this parameter instead. Then this check ins't necessary here.
>>>
>>> # Just FYI, MAX_SCHEDULE_TIMEOUT should be MAX_SCHEDULE_TIMEOUT/HZ here. 
>>>
>>> Thanks,
>>> Satoru
>>
>>  Yes, how about this :
> 
> I confirmed the followings.
> 
>  - 3.14-rc8: system hunged up with "hung_task_timeout_secs > LONG_MAX/HZ".
>  - 3.14-rc8 with your patch: works fine. I can't set the above mentioned value any more.
> 
> Writing possible values (0..LONG_MAX/HZ) in Documentation/sysctl/kernel.txt
> make this patch better.
> 
> Thanks,
> Satoru

Thanks to you attention and suggestion. I remade this patch as following.
Is it appropriate to be reposted with tag "PATCH v3"

Subject: [PATCH v3] hung_task : check the value of "sysctl_hung_task_timeout_sec"

As sysctl_hung_task_timeout_sec is unsigned long, when this value is
larger then LONG_MAX/HZ, the function schedule_timeout_interruptible in
watchdog will return immediately without sleep and with print :

[  205.452934] schedule_timeout: wrong timeout value ffffffffffffff83

and then the funtion watchdog will call schedule_timeout_interruptible
again and again. The screen will be filled with
	"schedule_timeout: wrong timeout value ffffffffffffff83"

This patch does some check and correction in sysctl, to let the
function schedule_timeout_interruptible allways get the valid parameter.

Signed-off-by: Liu Hua <sdu.liu@huawei.com>
Tested-by: Satoru Takeuchi <satoru.takeuchi@gmail.com>
---
 Documentation/sysctl/kernel.txt | 1 +
 kernel/sysctl.c                 | 6 ++++++
 2 files changed, 7 insertions(+)

diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index e55124e..855d9b3 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -317,6 +317,7 @@ 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.
+Possible values to set are in range {0..LONG_MAX/HZ}.

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

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 49e13e1..aae21e8 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -144,6 +144,11 @@ static int min_percpu_pagelist_fract = 8;
 static int ngroups_max = NGROUPS_MAX;
 static const int cap_last_cap = CAP_LAST_CAP;

+/*this is needed for proc_doulongvec_minmax of sysctl_hung_task_timeout_secs */
+#ifdef CONFIG_DETECT_HUNG_TASK
+static unsigned long hung_task_timeout_max = (LONG_MAX/HZ);
+#endif
+
 #ifdef CONFIG_INOTIFY_USER
 #include <linux/inotify.h>
 #endif
@@ -995,6 +1000,7 @@ static struct ctl_table kern_table[] = {
 		.maxlen		= sizeof(unsigned long),
 		.mode		= 0644,
 		.proc_handler	= proc_dohung_task_timeout_secs,
+		.extra2		= &hung_task_timeout_max,
 	},
 	{
 		.procname	= "hung_task_warnings",
-- 
1.9.0

Thanks,
Liu Hua

Re: [PATCH v2] hung_task : check the value of "sysctl_hung_task_timeout_sec"

[Satoru Takeuchi]

Hi Liu,

At Wed, 26 Mar 2014 15:56:58 +0800,
Liu hua wrote:
> 
> 于 2014/3/26 0:25, Satoru Takeuchi 写道:
> > At Tue, 25 Mar 2014 16:58:58 +0800,
> > Liu hua wrote:
> >>
> >> 于 2014/3/24 4:50, Satoru Takeuchi 写道:
> >>> At Sun, 23 Mar 2014 15:54:04 +0800,
> >>> Liu Hua wrote:
> >>>>
> >>>> As sysctl_hung_task_timeout_sec is unsigned long, when this value is
> >>>> larger then LONG_MAX/HZ, the function schedule_timeout_interruptible in
> >>>> watchdog will return immediately without sleep and with print :
> >>>>
> >>>> [  205.452934] schedule_timeout: wrong timeout value ffffffffffffff83
> >>>>
> >>>> and then the funtion watchdog will call schedule_timeout_interruptible again
> >>>> and again. The screen will be filled with
> >>>> 	"schedule_timeout: wrong timeout value ffffffffffffff83"
> >>>>
> >>>> This patch does some check and correction in timeout_jiffies, to let the
> >>>> function schedule_timeout_interruptible allways get the valid parameter.
> >>>>
> >>>> Cc: <stable@vger.kernel.org>
> >>>> Signed-off-by: Liu Hua <sdu.liu@huawei.com>
> >>>> ---
> >>>>  kernel/hung_task.c | 8 ++++++--
> >>>>  1 file changed, 6 insertions(+), 2 deletions(-)
> >>>>
> >>>> diff --git a/kernel/hung_task.c b/kernel/hung_task.c
> >>>> index 6df6149..f992286 100644
> >>>> --- a/kernel/hung_task.c
> >>>> +++ b/kernel/hung_task.c
> >>>> @@ -174,8 +174,12 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
> >>>>  
> >>>>  static unsigned long timeout_jiffies(unsigned long timeout)
> >>>>  {
> >>>> -	/* timeout of 0 will disable the watchdog */
> >>>> -	return timeout ? timeout * HZ : MAX_SCHEDULE_TIMEOUT;
> >>>> +	/* timeout of 0 or >= LONG_MAX/HZ will disable the watchdog */
> >>>> +	if ((timeout == 0) || (timeout > MAX_SCHEDULE_TIMEOUT))
> >>>
> >>> You should check whether sysctl_hung_task_timeout_sec > MAX_SCHEDULE_TIMEOUT/HZ
> >>> or not when setting this parameter instead. Then this check ins't necessary here.
> >>>
> >>> # Just FYI, MAX_SCHEDULE_TIMEOUT should be MAX_SCHEDULE_TIMEOUT/HZ here. 
> >>>
> >>> Thanks,
> >>> Satoru
> >>
> >>  Yes, how about this :
> > 
> > I confirmed the followings.
> > 
> >  - 3.14-rc8: system hunged up with "hung_task_timeout_secs > LONG_MAX/HZ".
> >  - 3.14-rc8 with your patch: works fine. I can't set the above mentioned value any more.
> > 
> > Writing possible values (0..LONG_MAX/HZ) in Documentation/sysctl/kernel.txt
> > make this patch better.
> > 
> > Thanks,
> > Satoru
> 
> Thanks to you attention and suggestion. I remade this patch as following.
> Is it appropriate to be reposted with tag "PATCH v3"
> 
> Subject: [PATCH v3] hung_task : check the value of "sysctl_hung_task_timeout_sec"

It looks good to me.

Thanks,
Satoru

> 
> As sysctl_hung_task_timeout_sec is unsigned long, when this value is
> larger then LONG_MAX/HZ, the function schedule_timeout_interruptible in
> watchdog will return immediately without sleep and with print :
> 
> [  205.452934] schedule_timeout: wrong timeout value ffffffffffffff83
> 
> and then the funtion watchdog will call schedule_timeout_interruptible
> again and again. The screen will be filled with
> 	"schedule_timeout: wrong timeout value ffffffffffffff83"
> 
> This patch does some check and correction in sysctl, to let the
> function schedule_timeout_interruptible allways get the valid parameter.
> 
> Signed-off-by: Liu Hua <sdu.liu@huawei.com>
> Tested-by: Satoru Takeuchi <satoru.takeuchi@gmail.com>
> ---
>  Documentation/sysctl/kernel.txt | 1 +
>  kernel/sysctl.c                 | 6 ++++++
>  2 files changed, 7 insertions(+)
> 
> diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
> index e55124e..855d9b3 100644
> --- a/Documentation/sysctl/kernel.txt
> +++ b/Documentation/sysctl/kernel.txt
> @@ -317,6 +317,7 @@ 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.
> +Possible values to set are in range {0..LONG_MAX/HZ}.
> 
>  ==============================================================
> 
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 49e13e1..aae21e8 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -144,6 +144,11 @@ static int min_percpu_pagelist_fract = 8;
>  static int ngroups_max = NGROUPS_MAX;
>  static const int cap_last_cap = CAP_LAST_CAP;
> 
> +/*this is needed for proc_doulongvec_minmax of sysctl_hung_task_timeout_secs */
> +#ifdef CONFIG_DETECT_HUNG_TASK
> +static unsigned long hung_task_timeout_max = (LONG_MAX/HZ);
> +#endif
> +
>  #ifdef CONFIG_INOTIFY_USER
>  #include <linux/inotify.h>
>  #endif
> @@ -995,6 +1000,7 @@ static struct ctl_table kern_table[] = {
>  		.maxlen		= sizeof(unsigned long),
>  		.mode		= 0644,
>  		.proc_handler	= proc_dohung_task_timeout_secs,
> +		.extra2		= &hung_task_timeout_max,
>  	},
>  	{
>  		.procname	= "hung_task_warnings",
> -- 
> 1.9.0
> 
> Thanks,
> Liu Hua
>