From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DB232C7618B for ; Wed, 24 Jul 2019 13:03:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B9ABE21901 for ; Wed, 24 Jul 2019 13:03:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727345AbfGXNDb (ORCPT ); Wed, 24 Jul 2019 09:03:31 -0400 Received: from metis.ext.pengutronix.de ([85.220.165.71]:54295 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726312AbfGXND2 (ORCPT ); Wed, 24 Jul 2019 09:03:28 -0400 Received: from heimdall.vpn.pengutronix.de ([2001:67c:670:205:1d::14] helo=blackshift.org) by metis.ext.pengutronix.de with esmtp (Exim 4.92) (envelope-from ) id 1hqGvW-0006gK-67; Wed, 24 Jul 2019 15:03:26 +0200 From: Marc Kleine-Budde To: netdev@vger.kernel.org Cc: davem@davemloft.net, linux-can@vger.kernel.org, kernel@pengutronix.de, Nikita Yushchenko , linux-stable , Marc Kleine-Budde Subject: [PATCH 2/7] can: rcar_canfd: fix possible IRQ storm on high load Date: Wed, 24 Jul 2019 15:03:17 +0200 Message-Id: <20190724130322.31702-3-mkl@pengutronix.de> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190724130322.31702-1-mkl@pengutronix.de> References: <20190724130322.31702-1-mkl@pengutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-SA-Exim-Connect-IP: 2001:67c:670:205:1d::14 X-SA-Exim-Mail-From: mkl@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: netdev@vger.kernel.org Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Nikita Yushchenko 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 Cc: linux-stable Signed-off-by: Marc Kleine-Budde --- drivers/net/can/rcar/rcar_canfd.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) 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; } -- 2.20.1