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=-8.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,USER_AGENT_MUTT 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 ECC76C43441 for ; Tue, 13 Nov 2018 04:31:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 976A5224E0 for ; Tue, 13 Nov 2018 04:31:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="H0420tbw" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 976A5224E0 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=roeck-us.net Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728758AbeKMO1m (ORCPT ); Tue, 13 Nov 2018 09:27:42 -0500 Received: from mail-pg1-f195.google.com ([209.85.215.195]:36229 "EHLO mail-pg1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726103AbeKMO1m (ORCPT ); Tue, 13 Nov 2018 09:27:42 -0500 Received: by mail-pg1-f195.google.com with SMTP id z17-v6so5077855pgv.3; Mon, 12 Nov 2018 20:31:26 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=VAdb5ULgmF6PRD2iWSOnSfqN5wEOlcOmJI3KVEm8qkU=; b=H0420tbw89YBwj3Mliaq5Yx/xd44sk/ZskWLrV2ZJsXNvupXvP1zqXbNFJtxdj4xiW HPRq0kI5UaTM/yyjzcJEPJULfQ0bIVVXEjzN4Egk0IQCx3Y/8kvw60wlES9EFZ395WBO XVagORFAM/0cMxxwlGwPDOty2/RoYuDeRbICkbfWvxEs7ll4WXzJjbzOiG41JAqISmI4 WZBTh5WsNfFVu1yF/EGQgzCpoB1rI2uPt8f4AHfFotwFNeJI45CkcLJhCenRbQPgQgeB SL+QT4Z7h3qh0SYRtxgfSRp1Im6P7/L/QUdjPmFvp4kaF/no65YCKPPCNQeUr0/hi8Nv V3iw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to:user-agent; bh=VAdb5ULgmF6PRD2iWSOnSfqN5wEOlcOmJI3KVEm8qkU=; b=rySk0EQUXcQvDoLsxp8FsRrovXEy0A2K/7iTy2L7wg6s02K107VOOrNoZcd/Mo318i 9btrfZw2G+K/aqTtz9XGIYpI09So+59PLPEFzemepU5bDTXa9ArUvwBmgmE+ndBJ2dQm RtuBqZla5+ebDmzyF35GWL4TEboYz9CWGwQZL2F9jKzHuDk+fe5cHozvUNLHYaLOGAlN MrpMhEQlhhL+6qf8Z9/YPF9d6YyzkO4t2XmdeoATD3Y3+RG8htc0DB9jSouOici4tTqK wksXKzn/SuhQ1KXeCy+cMgQM92bjs6AyyLY6uvMi+XsVZf6DmxodO2mG7GVmMNNW4mTD sKKg== X-Gm-Message-State: AGRZ1gItYor5Vqt8pJk3qwwGffSxHqaGa/+J6dnrDn6iHKAI5ZqyjkPJ Yk1mjUNq3Wdzr6Pgf6Ot55Q= X-Google-Smtp-Source: AJdET5f6jWujWwTQX94V7MiesSv/6EATVlxKoff3cwCD8tG25TlH3ZXwNo+y40yPDxjPktLwP6Nbng== X-Received: by 2002:a63:6ecf:: with SMTP id j198mr3412322pgc.3.1542083485512; Mon, 12 Nov 2018 20:31:25 -0800 (PST) Received: from localhost ([2600:1700:e321:62f0:329c:23ff:fee3:9d7c]) by smtp.gmail.com with ESMTPSA id r12sm12547189pgv.83.2018.11.12.20.31.23 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 12 Nov 2018 20:31:24 -0800 (PST) Date: Mon, 12 Nov 2018 20:31:22 -0800 From: Guenter Roeck To: Nicolin Chen Cc: jdelvare@suse.com, linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] hwmon (ina3221) Add mutex lock to shunt nodes Message-ID: <20181113043122.GA11205@roeck-us.net> References: <20181113042324.852-1-nicoleotsuka@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181113042324.852-1-nicoleotsuka@gmail.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 12, 2018 at 08:23:24PM -0800, Nicolin Chen wrote: > The shunt resistor values are used to calculate shunt voltages > and currents. As a part of sysfs nodes, it would be better to > get protected with the same mutex too as other sysfs ABI nodes, > although this is not very critical because the mutex was added > to mainly protect register access. > > So this patch adds the mutex lock to protect the shunt node. > I am missing something here. I don't see the point of this mutex. It just reads a variable and reports the result. When setting, it just writes a value. Protecting the conversion of the passed value with a mutex is pointless. Protecting writing the value against reading it is just as pointless. Guenter > Signed-off-by: Nicolin Chen > --- > drivers/hwmon/ina3221.c | 17 +++++++++++++++-- > 1 file changed, 15 insertions(+), 2 deletions(-) > > diff --git a/drivers/hwmon/ina3221.c b/drivers/hwmon/ina3221.c > index 86281afd2619..f7a09ab6c440 100644 > --- a/drivers/hwmon/ina3221.c > +++ b/drivers/hwmon/ina3221.c > @@ -532,8 +532,15 @@ static ssize_t ina3221_show_shunt(struct device *dev, > struct ina3221_data *ina = dev_get_drvdata(dev); > unsigned int channel = sd_attr->index; > struct ina3221_input *input = &ina->inputs[channel]; > + ssize_t ret; > > - return snprintf(buf, PAGE_SIZE, "%d\n", input->shunt_resistor); > + mutex_lock(&ina->lock); > + > + ret = snprintf(buf, PAGE_SIZE, "%d\n", input->shunt_resistor); > + > + mutex_unlock(&ina->lock); > + > + return ret; > } > > static ssize_t ina3221_set_shunt(struct device *dev, > @@ -547,14 +554,20 @@ static ssize_t ina3221_set_shunt(struct device *dev, > int val; > int ret; > > + mutex_lock(&ina->lock); > + > ret = kstrtoint(buf, 0, &val); > - if (ret) > + if (ret) { > + mutex_unlock(&ina->lock); > return ret; > + } > > val = clamp_val(val, 1, INT_MAX); > > input->shunt_resistor = val; > > + mutex_unlock(&ina->lock); > + > return count; > } > > -- > 2.17.1 >