On Wed, Oct 08, 2014 at 11:08:25AM -0400, Steven Rostedt wrote:
> > Steve, wth is that thing supposed to do?
> >
> > set_current_state(TASK_INTERRUPTIBLE);
> > while (!kthread_should_stop())
> > schedule();
> >
> > That looks broken alright. It'll revert to a yield() 'spin' loop if it
> > ever gets a wakeup for anything other than the kthread_stop().
> >
> > Did you mean to write something like:
> >
> > set_current_state(TASK_INTERRUPTIBLE);
> > while (!kthread_should_stop()) {
> > schedule();
> > set_current_state(TASK_INTERRUPTIBLE);
> > }
> > __set_current_state(TASK_RUNNING);
> >
> > ?
>
> Wow, what a blast from the past. That code hasn't been touched since
> 2009!
>
> Anyway, all that thread did was call test work on each cpu, and then
> waits to be killed. It should only get a single wake up and that should
> be from the kthread_stop() call. IOW, that loop should never be
> executed more than once.
>
> What exactly is the bug here?
The bug is as explained, the loop is wrong and will revert to a yield
'spin' loop after a single wakeup.
The debugging that caught it is that you exit the loop without setting
TASK_RUNNING.
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