netdev - Re: [PATCH] can: rcar_canfd: rcar_canfd_handle_global_receive(): fix IRQ storm on global FIFO receive

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Date:   Wed, 2 Nov 2022 02:36:43 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Biju Das <biju.das.jz@...renesas.com>
Cc:     Wolfgang Grandegger <wg@...ndegger.com>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        Pavel Machek <pavel@...x.de>, Sasha Levin <sashal@...nel.org>,
        linux-can@...r.kernel.org, netdev@...r.kernel.org,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Chris Paterson <chris.paterson2@...esas.com>,
        linux-renesas-soc@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] can: rcar_canfd: rcar_canfd_handle_global_receive(): fix
 IRQ storm on global FIFO receive

On Mon, Oct 31, 2022 at 09:04:20AM +0000, Biju Das wrote:
> commit 702de2c21eed04c67cefaaedc248ef16e5f6b293 upstream.
> 
> We are seeing an IRQ storm on the global receive IRQ line under heavy
> CAN bus load conditions with both CAN channels enabled.
> 
> Conditions:
> 
> The global receive IRQ line is shared between can0 and can1, either of
> the channels can trigger interrupt while the other channel's IRQ line
> is disabled (RFIE).
> 
> When global a receive IRQ interrupt occurs, we mask the interrupt in
> the IRQ handler. Clearing and unmasking of the interrupt is happening
> in rx_poll(). There is a race condition where rx_poll() unmasks the
> interrupt, but the next IRQ handler does not mask the IRQ due to
> NAPIF_STATE_MISSED flag (e.g.: can0 RX FIFO interrupt is disabled and
> can1 is triggering RX interrupt, the delay in rx_poll() processing
> results in setting NAPIF_STATE_MISSED flag) leading to an IRQ storm.
> 
> This patch fixes the issue by checking IRQ active and enabled before
> handling the IRQ on a particular channel.
> 
> Fixes: dd3bd23eb438 ("can: rcar_canfd: Add Renesas R-Car CAN FD driver")
> Suggested-by: Marc Kleine-Budde <mkl@...gutronix.de>
> Signed-off-by: Biju Das <biju.das.jz@...renesas.com>
> Link: https://lore.kernel.org/all/20221025155657.1426948-2-biju.das.jz@bp.renesas.com
> Cc: stable@...r.kernel.org # 4.9.x
> [mkl: adjust commit message]
> Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
> [biju: removed gpriv from RCANFD_RFCC_RFIE macro]
> Signed-off-by: Biju Das <biju.das.jz@...renesas.com>
> ---
> Resending to 4.9 with confilcts[1] fixed
> [1] https://lore.kernel.org/stable/OS0PR01MB59226F2443DFCE7C5D73778786379@OS0PR01MB5922.jpnprd01.prod.outlook.com/T/#t
> ---
>  drivers/net/can/rcar/rcar_canfd.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)

All now queued up, thanks.

greg k-h