[PATCH 3.12 083/155] hung_task: check the value of "sysctl_hung_task_timeout_sec"

From: Jiri Slaby
Date: Tue Apr 07 2015 - 09:15:56 EST

From: Liu Hua <sdu.liu@xxxxxxxxxx>

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


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@xxxxxxxxxx>
Tested-by: Satoru Takeuchi <satoru.takeuchi@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
kernel/sysctl.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 167741003616..6a9b0c42fb30 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -142,6 +142,11 @@ static int minolduid;
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 */
+static unsigned long hung_task_timeout_max = (LONG_MAX/HZ);
#include <linux/inotify.h>
@@ -971,6 +976,7 @@ 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",

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