On Tue, Apr 4, 2017 at 8:55 PM, Mike Galbraith <efa...@gmx.de> wrote: > On Tue, 2017-04-04 at 18:52 -0700, Cong Wang wrote: > >> diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c >> index 1a2f9e9..4725d2f 100644 >> --- a/net/sched/sch_generic.c >> +++ b/net/sched/sch_generic.c >> @@ -925,7 +925,7 @@ void dev_deactivate_many(struct list_head *head) >> /* Wait for outstanding qdisc_run calls. */ >> list_for_each_entry(dev, head, close_list) >> while (some_qdisc_is_busy(dev)) >> - yield(); >> + cond_resched(); >> } > > 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? 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.
