MassZero0 e00c8a7d38 linux: mts: fix NAPI poll storm that pins a CPU when the NIC MSI never fires (#14) ...

The PS5 GbE NIC has no INTx pin and its MSI sometimes never fires after a
cold boot. The driver already works around that with a 1 Hz link-poll
watchdog that kicks NAPI by hand.

But gbe_poll() re-checks GBE_REG_ISR after completing NAPI and reschedules
itself whenever a GBE_IER_MASK cause is still latched, without ever
acknowledging (W1C) the ISR -- only the hardware handler gbe_isr() does.
When the MSI is dead gbe_isr() never runs, so the latched cause (e.g.
RX_DONE) is never cleared, the re-check stays true forever, and NAPI
reschedules itself ~30k times/s, pinning ksoftirqd on that CPU at 100%.

Acknowledge the pending causes before re-kicking so a stale, undelivered
cause can no longer spin NAPI.

While the MSI is dead also poll the rings every GBE_POLL_FALLBACK_MS (10 ms)
instead of once per second, so interactive RX latency drops from ~1 s to a
few ms; fall back to HZ as soon as real IRQs start arriving.

2026-06-01 21:54:28 +02:00

327 KiB

Raw Permalink Blame History

View Raw