[PATCH 3.8 127/133] hung_task: check the value of "sysctl_hung_task_timeout_sec"

[Kamal Mostafa]

3.8.13.22 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Liu Hua <sdu.liu at huawei.com>

commit 80df28476505ed4e6701c3448c63c9229a50c655 upstream.

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 :

  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 at huawei.com>
Tested-by: Satoru Takeuchi <satoru.takeuchi at gmail.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 kernel/sysctl.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 585015f..e17ddf6 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -145,6 +145,11 @@ 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
@@ -950,6 +955,7 @@ 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",
-- 
1.9.1