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From f64aaea45c16fd3f34e4130b62a14389fb174b13 Mon Sep 17 00:00:00 2001
From: Vladimir Barinov <vladimir.barinov@cogentembedded.com>
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 <nikita.yoush@cogentembedded.com>
Signed-off-by: Vladimir Barinov <vladimir.barinov@cogentembedded.com>
---
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
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