From nobody Sun Jun 28 04:44:19 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9DCEDC4332F for ; Mon, 14 Feb 2022 23:48:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232218AbiBNXsw (ORCPT ); Mon, 14 Feb 2022 18:48:52 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:37022 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229665AbiBNXsu (ORCPT ); Mon, 14 Feb 2022 18:48:50 -0500 Received: from smtp.smtpout.orange.fr (smtp05.smtpout.orange.fr [80.12.242.127]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 918F71402E for ; Mon, 14 Feb 2022 15:48:40 -0800 (PST) Received: from localhost.localdomain ([124.33.176.97]) by smtp.orange.fr with ESMTPA id Jl4ynKYlVPEU7Jl59na5Tp; Tue, 15 Feb 2022 00:48:37 +0100 X-ME-Helo: localhost.localdomain X-ME-Auth: MDU0YmViZGZmMDIzYiBlMiM2NTczNTRjNWZkZTMwOGRiOGQ4ODf3NWI1ZTMyMzdiODlhOQ== X-ME-Date: Tue, 15 Feb 2022 00:48:37 +0100 X-ME-IP: 124.33.176.97 From: Vincent Mailhol To: netdev@vger.kernel.org, linux-can@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Marc Kleine-Budde , Maximilian Schneider , Vincent Mailhol Subject: [RFC PATCH v1] can: gs_usb: change active_channels's type from atomic_t to u8 Date: Tue, 15 Feb 2022 08:48:14 +0900 Message-Id: <20220214234814.1321599-1-mailhol.vincent@wanadoo.fr> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" The driver uses an atomic_t variable: gs_usb:active_channels to keep track of the number of opened channels in order to only allocate memory for the URBs when this count changes from zero to one. However, the driver does not decrement the counter when an error occurs in gs_can_open(). This issue is fixed by changing the type from atomic_t to u8 and by simplifying the logic accordingly. It is safe to use an u8 here because the network stack big kernel lock (a.k.a. rtnl_mutex) is being hold. For details, please refer to [1]. [1] https://lore.kernel.org/linux-can/CAMZ6Rq+sHpiw34ijPsmp7vbUpDtJwvVtdV7C= vRZJsLixjAFfrg@mail.gmail.com/T/#t Fixes: d08e973a77d1 ("can: gs_usb: Added support for the GS_USB CAN devices") Signed-off-by: Vincent Mailhol --- drivers/net/can/usb/gs_usb.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/drivers/net/can/usb/gs_usb.c b/drivers/net/can/usb/gs_usb.c index b487e3fe770a..d35749fad1ef 100644 --- a/drivers/net/can/usb/gs_usb.c +++ b/drivers/net/can/usb/gs_usb.c @@ -191,8 +191,8 @@ struct gs_can { struct gs_usb { struct gs_can *canch[GS_MAX_INTF]; struct usb_anchor rx_submitted; - atomic_t active_channels; struct usb_device *udev; + u8 active_channels; }; =20 /* 'allocate' a tx context. @@ -589,7 +589,7 @@ static int gs_can_open(struct net_device *netdev) if (rc) return rc; =20 - if (atomic_add_return(1, &parent->active_channels) =3D=3D 1) { + if (!parent->active_channels) { for (i =3D 0; i < GS_MAX_RX_URBS; i++) { struct urb *urb; u8 *buf; @@ -690,6 +690,7 @@ static int gs_can_open(struct net_device *netdev) =20 dev->can.state =3D CAN_STATE_ERROR_ACTIVE; =20 + parent->active_channels++; if (!(dev->can.ctrlmode & CAN_CTRLMODE_LISTENONLY)) netif_start_queue(netdev); =20 @@ -705,7 +706,8 @@ static int gs_can_close(struct net_device *netdev) netif_stop_queue(netdev); =20 /* Stop polling */ - if (atomic_dec_and_test(&parent->active_channels)) + parent->active_channels--; + if (!parent->active_channels) usb_kill_anchored_urbs(&parent->rx_submitted); =20 /* Stop sending URBs */ @@ -984,8 +986,6 @@ static int gs_usb_probe(struct usb_interface *intf, =20 init_usb_anchor(&dev->rx_submitted); =20 - atomic_set(&dev->active_channels, 0); - usb_set_intfdata(intf, dev); dev->udev =3D interface_to_usbdev(intf); =20 --=20 2.34.1