On Wed, Mar 04, 2020 at 01:39:41PM -0800, Xi Wang wrote: > The main purpose of kernel watchdog is to test whether scheduler can > still schedule tasks on a cpu. In order to reduce latency from > periodically invoking watchdog reset in thread context, we can simply > touch watchdog from pick_next_task in scheduler. Compared to actually > resetting watchdog from cpu stop / migration threads, we lose coverage > on: a migration thread actually get picked and we actually context > switch to the migration thread. Both steps are heavily protected by > kernel locks and unlikely to silently fail. Thus the change would > provide the same level of protection with less overhead. > > The new way vs the old way to touch the watchdogs is configurable > from: > > /proc/sys/kernel/watchdog_touch_in_thread_interval > > The value means: > 0: Always touch watchdog from pick_next_task > 1: Always touch watchdog from migration thread > N (N>0): Touch watchdog from migration thread once in every N > invocations, and touch watchdog from pick_next_task for > other invocations. > This is configurable madness. What are we really trying to do here?
