On Thu, 17 Dec 2015 21:23:03 +0900 Tetsuo Handa <[email protected]> wrote:
> >From 529ff00b556e110c6e801c39e94b06f559307136 Mon Sep 17 00:00:00 2001 > From: Tetsuo Handa <[email protected]> > Date: Thu, 17 Dec 2015 16:27:08 +0900 > Subject: [PATCH] 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. This seems like reasonable behaviour, but it is a non-backward-compatible change. I don't know how important that is - probably "not very". Please let's fully describe this behaviour in the documentation. Documentation/sysctl/kernel.txt. It appears that if userspace writes a new timeout which has already expired, a check is triggered immediately, correct? Let's ensure that this is documented as well. And tested! And it would be helpful to add a comment to hung_timeout_jiffies() which describes the behaviour and explains the reasons for it. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
