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=-16.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 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 E99DFC4338F for ; Sat, 31 Jul 2021 17:51:45 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 99AB461050 for ; Sat, 31 Jul 2021 17:51:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 99AB461050 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=o1ZVYUY9hwnbCrEaYbivVKeb/wWwQk9uf/QHVoqqui0=; b=gRwGstOP2HGxN2 rh/W8aVMjPPTcgS6oUT/SQNrGmrRE0VKC+hOH48ZK6/4xtbU0T0PhxFUQiHvNOkT3olxzgmfcZRUZ s0M1PoICWlsCGx9GyBdO+qmgVgkQjsa1T7fRh/XKEDVnRLuyuo42szaatwyF+/hGD4mJlIf2x0aqs W78q8ftheGnDxN2CnGcshclplro2PX1pA9vF4pFE25p+aL0x2TgbumjZ1jK1XMuF2dgZumCmy5AlT LiIZNBPadL+TKlG6dgVRSZpKtLB6GUgq97mHiyns9+OWYApIXrKitDOtJItflXripen8TyVT71kYn xSIiHmMRbmNRNBRsvGsg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1m9t7F-00C14H-6d; Sat, 31 Jul 2021 17:49:41 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1m9t7B-00C13k-Tq; Sat, 31 Jul 2021 17:49:39 +0000 Received: from jic23-huawei (cpc108967-cmbg20-2-0-cust86.5-4.cable.virginm.net [81.101.6.87]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 11CD661042; Sat, 31 Jul 2021 17:49:31 +0000 (UTC) Date: Sat, 31 Jul 2021 18:52:10 +0100 From: Jonathan Cameron To: "hui.liu" Cc: , , , , , , , , , , , , , , Subject: Re: [PATCH] iio: mtk-auxadc: add mutex_destroy Message-ID: <20210731185210.7acb5f79@jic23-huawei> In-Reply-To: <1627300994.11261.11.camel@mhfsdcap03> References: <20210715093523.29844-1-hui.liu@mediatek.com> <20210715093523.29844-2-hui.liu@mediatek.com> <20210717174432.7e69e4e9@jic23-huawei> <1627042875.27985.15.camel@mhfsdcap03> <20210724183003.6f3bc1d5@jic23-huawei> <1627300994.11261.11.camel@mhfsdcap03> X-Mailer: Claws Mail 4.0.0 (GTK+ 3.24.30; x86_64-pc-linux-gnu) MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210731_104938_051553_6B8137F9 X-CRM114-Status: GOOD ( 48.76 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, 26 Jul 2021 20:03:14 +0800 hui.liu wrote: > On Sat, 2021-07-24 at 18:30 +0100, Jonathan Cameron wrote: > > On Fri, 23 Jul 2021 20:21:15 +0800 > > hui.liu wrote: > > > > > On Sat, 2021-07-17 at 17:44 +0100, Jonathan Cameron wrote: > > > > On Thu, 15 Jul 2021 17:35:23 +0800 > > > > Hui Liu wrote: > > > > > > > > > Add mutex_destroy when probe fail and remove device. > > > > > > > > > > Signed-off-by: Hui Liu > > > > Hi Hui Liu, > > > > > > > > We very very rarely bother to call mutex_destroy(). The reason is > > > > that it is only a non noop in when mutex debugging is enabled and > > > > that is only useful if there is a plausible route in which it could > > > > be used after the mutex_destroy. Given these are both at the ends > > > > of removal paths, I don't think this is useful. That's why you will > > > > rarely find mutex_destroy() being called. > > > > > > > > Thanks, > > > > > > > > Jonathan > > > > > > Hi Jonathon, > > > > > > I think this patch could assurance the integrity of code. > > > mutex_init will be called when driver probe. If driver probe fail or > > > device removed, mutex_destroy could set lock->magic to NULL. > > > > I'm not seeing the use case here given the location doesn't leave > > a huge amount of code that could have such a bug. There might have been > > something if we had any route to increment the reference count of the > > structure this mutex is ultimately embedded in and so have it outlast > > the remove function or error path. In this driver it looks like there is > > no such path. Hence you are protecting against a automated > > cleanup of core code (nothing in the driver itself) which is obviously > > not going to try taking a driver specific mutex. > > > > A few side notes: > > > > You are calling it wrong place in remove. The ordering in remove > > should be the opposite of that in probe so the mutex_destroy should either > > be a few lines earlier, or you should have a comment there to say why you > > are doing it where you have chosen to do so. > > > > The style of this probe is to do error handling in a block at the end. > > So this handling should be there, not in the if statement. > > > > Jonathan > > > > > Hi Jonathon, > > Base on your helpful opinion, We will to do two changes in patch v2. > 1. In probe: move mutex_destroy from the if statement to error handling > path(err_power_off). > 2. In remove: calling mutex_destroy right after iio_device_unregister. > > Do we need some more change? Thanks. Ah. Sorry I missed this in the flood of emails during the week. Anyhow, I've replied to the v1 posting. Jonathan > > > > > > > > Thanks. > > > Hui > > > > > > > > > > > > --- > > > > > drivers/iio/adc/mt6577_auxadc.c | 2 ++ > > > > > 1 file changed, 2 insertions(+) > > > > > > > > > > diff --git a/drivers/iio/adc/mt6577_auxadc.c b/drivers/iio/adc/mt6577_auxadc.c > > > > > index 79c1dd68b909..d57243037ad6 100644 > > > > > --- a/drivers/iio/adc/mt6577_auxadc.c > > > > > +++ b/drivers/iio/adc/mt6577_auxadc.c > > > > > @@ -289,6 +289,7 @@ static int mt6577_auxadc_probe(struct platform_device *pdev) > > > > > ret = iio_device_register(indio_dev); > > > > > if (ret < 0) { > > > > > dev_err(&pdev->dev, "failed to register iio device\n"); > > > > > + mutex_destroy(&adc_dev->lock); > > > > > goto err_power_off; > > > > > } > > > > > > > > > > @@ -313,6 +314,7 @@ static int mt6577_auxadc_remove(struct platform_device *pdev) > > > > > 0, MT6577_AUXADC_PDN_EN); > > > > > > > > > > clk_disable_unprepare(adc_dev->adc_clk); > > > > > + mutex_destroy(&adc_dev->lock); > > > > > > > > > > return 0; > > > > > } > > > > > > > > > > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel