On Tue, 2019-09-24 at 18:05 +0200, Sebastian Andrzej Siewior wrote: > On 2019-09-24 10:47:36 [-0500], Scott Wood wrote: > > When the stop machine finishes it will do a wake_up_process() via > > complete(). Since this does not pass WF_LOCK_SLEEPER, saved_state will > > be > > cleared, and you'll have TASK_RUNNING when you get to other_func() and > > schedule(), regardless of whether CPU1 sends wake_up() -- so this change > > doesn't actually accomplish anything. > > True, I completely missed that part. > > > While as noted in the other thread I don't think these spurious wakeups > > are > > a huge problem, we could avoid them by doing stop_one_cpu_nowait() and > > then > > schedule() without messing with task state. Since we're stopping our > > own > > cpu, it should be guaranteed that the stopper has finished by the time > > we > > exit schedule(). > > I remember loosing a state can be a problem. Lets say it is not "just" > TASK_UNINTERRUPTIBLE -> TASK_RUNNING which sounds harmless but it is > __TASK_TRACED and you lose it as part of unlocking siglock.
OK, sounds like stop_one_cpu_nowait() is the way to go then. -Scott
