When poll() is called via netmap, txsync is initially called, and if there are no available buffers to reclaim, it waits for the driver to notify of new buffers. Since the TX IRQ is generally not used in iflib drivers, this ends up causing a timeout. Work around this by having the reclaim DELAY(1) if it's initially unable to reclaim anything, then schedule the tx task, which will spin by continuously rescheduling itself until some buffers are reclaimed. In general, the delay is enough to allow some buffers to be reclaimed, so spinning is minimized. Reported by: Johannes Lundberg <johalun0@gmail.com> Reviewed by: sbruno Sponsored by: Limelight Networks Differential Revision: https://reviews.freebsd.org/D15455
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