The patch titled
Subject: kernel/hung_task.c: use timeout diff when timeout is updated
has been added to the -mm tree. Its filename is
kernel-hung_taskc-use-timeout-diff-when-timeout-is-updated.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/kernel-hung_taskc-use-timeout-diff-when-timeout-is-updated.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/kernel-hung_taskc-use-timeout-diff-when-timeout-is-updated.patch
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------------------------------------------------------
From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Subject: kernel/hung_task.c: use timeout diff when timeout is updated
When new timeout is written to /proc/sys/kernel/hung_task_timeout_secs,
khungtaskd is interrupted and again sleeps for full timeout duration.
This means that hang task will not be checked if new timeout is written
periodically within old timeout duration and/or checking of hang task will
be delayed for up to previous timeout duration. Fix this by remembering
last time khungtaskd checked hang task.
This change will allow other watchdog tasks (if any) to share khungtaskd
by sleeping for minimal timeout diff of all watchdog tasks. Doing more
watchdog tasks from khungtaskd will reduce the possibility of printk()
collisions by multiple watchdog threads.
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Aaron Tomlin <atomlin@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/hung_task.c | 21 +++++++++++++--------
1 file changed, 13 insertions(+), 8 deletions(-)
diff -puN kernel/hung_task.c~kernel-hung_taskc-use-timeout-diff-when-timeout-is-updated kernel/hung_task.c
--- a/kernel/hung_task.c~kernel-hung_taskc-use-timeout-diff-when-timeout-is-updated
+++ a/kernel/hung_task.c
@@ -185,10 +185,12 @@ static void check_hung_uninterruptible_t
rcu_read_unlock();
}
-static unsigned long timeout_jiffies(unsigned long timeout)
+static long hung_timeout_jiffies(unsigned long last_checked,
+ unsigned long timeout)
{
/* timeout of 0 will disable the watchdog */
- return timeout ? timeout * HZ : MAX_SCHEDULE_TIMEOUT;
+ return timeout ? last_checked - jiffies + timeout * HZ :
+ MAX_SCHEDULE_TIMEOUT;
}
/*
@@ -224,18 +226,21 @@ EXPORT_SYMBOL_GPL(reset_hung_task_detect
*/
static int watchdog(void *dummy)
{
+ unsigned long hung_last_checked = jiffies;
+
set_user_nice(current, 0);
for ( ; ; ) {
unsigned long timeout = sysctl_hung_task_timeout_secs;
+ long t = hung_timeout_jiffies(hung_last_checked, timeout);
- while (schedule_timeout_interruptible(timeout_jiffies(timeout)))
- timeout = sysctl_hung_task_timeout_secs;
-
- if (atomic_xchg(&reset_hung_task, 0))
+ if (t <= 0) {
+ if (!atomic_xchg(&reset_hung_task, 0))
+ check_hung_uninterruptible_tasks(timeout);
+ hung_last_checked = jiffies;
continue;
-
- check_hung_uninterruptible_tasks(timeout);
+ }
+ schedule_timeout_interruptible(t);
}
return 0;
_
Patches currently in -mm which might be from penguin-kernel@xxxxxxxxxxxxxxxxxxx are
kernel-hung_taskc-use-timeout-diff-when-timeout-is-updated.patch
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