kernel/hung_task.c: use timeout diff when timeout is updated
authorTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Tue, 22 Mar 2016 21:24:39 +0000 (14:24 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Tue, 22 Mar 2016 22:36:02 +0000 (15:36 -0700)
commitb4aa14a63cb3194d8eab355fcee194838ab09121
tree84e104cac5b6ed9a629ea5c5d3e9c56e2c332db4
parent3f2b1a04f44933f2d6fe0a9bf9a9c1c452df23f7
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@I-love.SAKURA.ne.jp>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Aaron Tomlin <atomlin@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
kernel/hung_task.c