On Tue, 2017-04-04 at 22:19 -0700, Cong Wang wrote:
> On Tue, Apr 4, 2017 at 8:55 PM, Mike Galbraith <[email protected]> wrote:
> > That won't help, cond_resched() has the same impact upon a lone
> > SCHED_FIFO task as yield() does.. none.
>
> Hmm? In the comment you quote:
>
> * If you want to use yield() to wait for something, use wait_event().
> * If you want to use yield() to be 'nice' for others, use cond_resched().
>
> So if cond_resched() doesn't help, why this misleading comment?
This is not an oh let's be nice guys thing, it's a perfect match of...
<copy/paste>
* while (!event)
* yield();
(/copy/paste>
..get off the CPU until this happens thing. With nobody to yield the C
PU to, some_qdisc_is_busy() will remain true forever more.
> I picked the latter one, because the former is harder to implement
> properly (at least for -net) we need qdisc's to notify this waiter once
> they finish transmitting packets, which means we probably need
> a per-netdevice wait struct.
Yup, why I merely notified net-fu masters of lurking spinner. I met it
because I sometimes run most kthreads at prio 1, some prioritized, and
kworkers at prio 2. (never mind why, but they're excellent reasons)
-Mike
