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

[Liu hua]

ä 2014/3/24 4:50, Satoru Takeuchi åé:
> 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@xxxxxxxxxxxxxxx>
>> Signed-off-by: Liu Hua <sdu.liu@xxxxxxxxxx>
>> ---
>>  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
>>
>> --
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> 
> .
> 


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