The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From d4b890aec4bea7334ca2ca56fd3b12fb48a00cd1 Mon Sep 17 00:00:00 2001
From: Nikita Yushchenko nikita.yoush@cogentembedded.com Date: Wed, 26 Jun 2019 16:08:48 +0300 Subject: [PATCH] can: rcar_canfd: 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.
Fixes: dd3bd23eb438 ("can: rcar_canfd: Add Renesas R-Car CAN FD driver") Signed-off-by: Nikita Yushchenko nikita.yoush@cogentembedded.com Cc: linux-stable stable@vger.kernel.org Signed-off-by: Marc Kleine-Budde mkl@pengutronix.de
diff --git a/drivers/net/can/rcar/rcar_canfd.c b/drivers/net/can/rcar/rcar_canfd.c index 05410008aa6b..de34a4b82d4a 100644 --- a/drivers/net/can/rcar/rcar_canfd.c +++ b/drivers/net/can/rcar/rcar_canfd.c @@ -1508,10 +1508,11 @@ static int rcar_canfd_rx_poll(struct napi_struct *napi, int quota)
/* All packets processed */ if (num_pkts < quota) { - napi_complete_done(napi, num_pkts); - /* Enable Rx FIFO interrupts */ - rcar_canfd_set_bit(priv->base, RCANFD_RFCC(ridx), - RCANFD_RFCC_RFIE); + if (napi_complete_done(napi, num_pkts)) { + /* Enable Rx FIFO interrupts */ + rcar_canfd_set_bit(priv->base, RCANFD_RFCC(ridx), + RCANFD_RFCC_RFIE); + } } return num_pkts; }