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 :

  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>
Cc: <stable@vger.kernel.org>	[3.4+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index 271a09db6629f539753b864a567e78f011d0efde..9886c3d57fc2ad82d002e3fe3edfa60584f8cdaa 100644 (file)
--- 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 5c14b547882ef1dabfcd9cd80f5903e173ef4ec4..74f5b580fe34904fa4d9bcb2790545a323367773 100644 (file)
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -141,6 +141,11 @@ 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
@@ -985,6 +990,7 @@ 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",