On Wed, 24 Feb 2021 16:16:58 -0800 Wei Wang wrote: > On Wed, Feb 24, 2021 at 4:11 PM Alexander Duyck <alexanderdu...@fb.com> wrote: > > > > The problem with adding a bit for SCHED_THREADED is that you would > > have to heavily modify napi_schedule_prep so that it would add the > > bit. That is the reason for going with adding the bit to the busy > > poll logic because it added no additional overhead. Adding another > > atomic bit setting operation or heavily modifying the existing one > > would add considerable overhead as it is either adding a > > complicated conditional check to all NAPI calls, or adding an > > atomic operation to the path for the threaded NAPI. > > Please help hold on to the patch for now. I think Martin is still > seeing issues on his setup even with this patch applied. I have not > yet figured out why. But I think we should not merge this patch until > the issue is cleared. Will update this thread with progress.
If I'm looking right __busy_poll_stop() is only called if the last napi poll used to re-enable IRQs consumed full budget. You need to clear your new bit in busy_poll_stop(), not in __busy_poll_stop(). That will fix the case when hand off back to the normal poller (sirq, or thread) happens without going thru __napi_schedule().
