On Tue, Apr 04, 2017 at 10:25:19PM -0700, Cong Wang wrote: > On Tue, Apr 4, 2017 at 8:20 PM, Mike Galbraith <efa...@gmx.de> wrote: > > - while (some_qdisc_is_busy(dev)) > > - yield(); > > + swait_event_timeout(swait, !some_qdisc_is_busy(dev), 1); > > } > > I don't see why this is an improvement even if I don't care about the > hardcoded timeout for now... Why the scheduler can make a better > decision with swait_event_timeout() than with cond_resched()?
cond_resched() might be a no-op. and doing yield() will result in a priority inversion deadlock. Imagine the task doing yield() being the top priority (fifo99) task in the system. Then it will simply spin forever, not giving whatever task is required to make your condition true time to run.
