[PATCH v2 0/6] examples/l3fwd-power: fix Rx interrupt mode for shared FD PMDs

[Maxime Leroy <maxime@leroys.fr>]

l3fwd-power's Rx interrupt (one-shot) mode was written around NICs whose
interrupt fd is assigned per queue at setup, stays fixed and is
level-triggered, as on MSI-X hardware. PMDs that do not fit that model
never sleep on interrupts: they either fail to arm, watch an unbound fd,
or miss the wake, and the 10 ms poll timeout hides all of it.

dpaa2 is the motivating example: it delivers Rx interrupts through one
QBMan portal per lcore, so the queues of a lcore share a single fd that
is bound when the interrupt is enabled, not at queue setup; the
notification is edge-triggered on an empty to non-empty transition; and
arming a queue that already holds traffic returns -EAGAIN with the queue
left unarmed.

This series makes the interrupt and legacy loops handle those cases
while leaving MSI-X NICs unchanged:

  1/6 factor the duplicated arm/sleep/disarm block into a helper.
  2/6 check the arm return: on -EAGAIN poll and retry, on any other
      error drop interrupt mode for the lcore instead of sleeping on
      unarmed queues.
  3/6 register the fd in the epoll set after arming, not before, so a
      fd bound at enable time is watched only once it exists.
  4/6 accept -EEXIST when several queues share one fd.
  5/6 recheck the queues before sleeping so a packet that arrived during
      the arm window is not missed under edge-triggered interrupts.
  6/6 block indefinitely instead of on a 10 ms timeout, and wake the
      workers through an eventfd on exit, so a broken interrupt path no
      longer hides behind periodic polling.

v2:
  - 3/6: keep the registration state in struct lcore_conf instead of
    passing it to rx_interrupt_wait(), and restore the "RX interrupt
    won't enable." notice, now logged from the arm error path
    (David Marchand)

Maxime Leroy (6):
  examples/l3fwd-power: factor out Rx interrupt sleep path
  examples/l3fwd-power: check Rx interrupt enable errors
  examples/l3fwd-power: enable Rx interrupt before epoll add
  examples/l3fwd-power: accept shared Rx interrupt FD
  examples/l3fwd-power: recheck Rx queues before sleeping
  examples/l3fwd-power: block until Rx interrupt or exit

 examples/l3fwd-power/main.c | 187 +++++++++++++++++++++++++++++-------
 1 file changed, 153 insertions(+), 34 deletions(-)


base-commit: d55ccd4e6de64e3f797f60de9e81f1d60f849775
-- 
2.43.0