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=-16.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 BC0DDC4320E for ; Sun, 25 Jul 2021 06:33:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9771E60F23 for ; Sun, 25 Jul 2021 06:33:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230258AbhGYFwf (ORCPT ); Sun, 25 Jul 2021 01:52:35 -0400 Received: from mail.kernel.org ([198.145.29.99]:43510 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229460AbhGYFwe (ORCPT ); Sun, 25 Jul 2021 01:52:34 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 1501760F13; Sun, 25 Jul 2021 06:33:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1627194784; bh=wlXW6USsZex8XdiwmwtjzhgxjC6oifv3Uj+wH6B39gM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=lmT3R1OgC+HAe1MwvwkIeU+qo8cAgYd34TMKQfMqAngmhTXkemgZvp9jthyRHAYdW goc+oAwqSYX3M5VX66MGJzFzocozaH6KO/0dBJ7/2rjefSU3adu+Vm3Wo0VY641aCI I6CYsDKQ3UQBvxMpgqGTb0RDyncXKcwXZPbNJJnk= Date: Sun, 25 Jul 2021 08:33:01 +0200 From: Greg KH To: Hin-Tak Leung Cc: Herton Ronaldo Krzesinski , Larry Finger , Kalle Valo , "David S. Miller" , Jakub Kicinski , Salah Triki , linux-wireless@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] wireless: rtl8187: replace udev with usb_get_dev() Message-ID: References: <20210724183457.GA470005@pc> <53895498.1259278.1627160074135@mail.yahoo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <53895498.1259278.1627160074135@mail.yahoo.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jul 24, 2021 at 08:54:34PM +0000, Hin-Tak Leung wrote: > > > On Saturday, 24 July 2021, 19:35:12 BST, Salah Triki wrote: > > > > Replace udev with usb_get_dev() in order to make code cleaner. > > > Signed-off-by: Salah Triki > > --- > > drivers/net/wireless/realtek/rtl818x/rtl8187/dev.c | 4 +--- > > 1 file changed, 1 insertion(+), 3 deletions(-) > > > diff --git a/drivers/net/wireless/realtek/rtl818x/rtl8187/dev.c b/drivers/net/wireless/realtek/rtl818x/rtl8187/dev.c > > index eb68b2d3caa1..30bb3c2b8407 100644 > > --- a/drivers/net/wireless/realtek/rtl818x/rtl8187/dev.c > > +++ b/drivers/net/wireless/realtek/rtl818x/rtl8187/dev.c > > @@ -1455,9 +1455,7 @@ static int rtl8187_probe(struct usb_interface *intf, > > >     SET_IEEE80211_DEV(dev, &intf->dev); > >     usb_set_intfdata(intf, dev); > > -    priv->udev = udev; > > - > > -    usb_get_dev(udev); > > +    priv->udev = usb_get_dev(udev); > > >     skb_queue_head_init(&priv->rx_queue); > > > -- > > 2.25.1 > > It is not cleaner - the change is not functionally equivalent. Before the change, the reference count is increased after the assignment; and after the change, before the assignment. So my question is, does the reference count increasing a little earlier matters? What can go wrong between very short time where the reference count increases, and priv->udev not yet assigned? I think there might be a race condition where the probbe function is called very shortly twice. > Especially if the time of running the reference count function is non-trivial. Probe functions are called in order, this should not be an issue. This patch changes nothing, I do not think it is needed at all. thanks, greg k-h