From f64aaea45c16fd3f34e4130b62a14389fb174b13 Mon Sep 17 00:00:00 2001 From: Vladimir Barinov Date: Thu, 30 Jan 2020 13:17:42 +0300 Subject: [PATCH] net: can: rcar_can: fix possible IRQ storm on high load We have observed rcar_canfd driver entering IRQ storm under high load, with following scenario: - rcar_canfd_global_interrupt() in entered due to Rx available, - napi_schedule_prep() is called, and sets NAPIF_STATE_SCHED in state - Rx fifo interrupts are masked, - rcar_canfd_global_interrupt() is entered again, this time due to error interrupt (e.g. due to overflow), - since scheduled napi poller has not yet executed, condition for calling napi_schedule_prep() from rcar_canfd_global_interrupt() remains true, thus napi_schedule_prep() gets called and sets NAPIF_STATE_MISSED flag in state, - later, napi poller function rcar_canfd_rx_poll() gets executed, and calls napi_complete_done(), - due to NAPIF_STATE_MISSED flag in state, this call does not clear NAPIF_STATE_SCHED flag from state, - on return from napi_complete_done(), rcar_canfd_rx_poll() unmasks Rx interrutps, - Rx interrupt happens, rcar_canfd_global_interrupt() gets called and calls napi_schedule_prep(), - since NAPIF_STATE_SCHED is set in state at this time, this call returns false, - due to that false return, rcar_canfd_global_interrupt() returns without masking Rx interrupt - and this results into IRQ storm: unmasked Rx interrupt happens again and again is misprocessed in the same way. This patch fixes that scenario by unmasking Rx interrupts only when napi_complete_done() returns true, which means it has cleared NAPIF_STATE_SCHED in state. Signed-off-by: Nikita Yushchenko Signed-off-by: Vladimir Barinov --- drivers/net/can/rcar/rcar_can.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/drivers/net/can/rcar/rcar_can.c b/drivers/net/can/rcar/rcar_can.c index 8d2c709..b06bfc2 100644 --- a/drivers/net/can/rcar/rcar_can.c +++ b/drivers/net/can/rcar/rcar_can.c @@ -705,9 +705,10 @@ static int rcar_can_rx_poll(struct napi_struct *napi, int quota) } /* All packets processed */ if (num_pkts < quota) { - napi_complete_done(napi, num_pkts); - priv->ier |= RCAR_CAN_IER_RXFIE; - writeb(priv->ier, &priv->regs->ier); + if (napi_complete_done(napi, num_pkts)) { + priv->ier |= RCAR_CAN_IER_RXFIE; + writeb(priv->ier, &priv->regs->ier); + } } return num_pkts; } -- 2.7.4