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=-5.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 16449C48BE8 for ; Tue, 15 Jun 2021 19:04:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E4066610EA for ; Tue, 15 Jun 2021 19:04:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231283AbhFOTGE (ORCPT ); Tue, 15 Jun 2021 15:06:04 -0400 Received: from so254-9.mailgun.net ([198.61.254.9]:27609 "EHLO so254-9.mailgun.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231228AbhFOTGD (ORCPT ); Tue, 15 Jun 2021 15:06:03 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1623783839; h=Content-Transfer-Encoding: Content-Type: In-Reply-To: MIME-Version: Date: Message-ID: From: References: Cc: To: Subject: Sender; bh=zyP2fQXFjwwDeB2EvHRFt1B8KSq55Tn5N6T3MM9RaWw=; b=xSTaQEf6krwH27DkTHpAg79ZYmymn1yxWeZTxJxbP6gfmaN5bG4Ms0d+l4tEGj6DhNDA8AFV DUWjyVRlKh6PwVFadSP+75fMZILTfvRxXOeNzu71h4IO0q4FqBHDpmanQqnsWVLiQxXdSWJv c8/CXt8uwWo4R85aQggeRv15svQ= X-Mailgun-Sending-Ip: 198.61.254.9 X-Mailgun-Sid: WyI4ZWZiZiIsICJsaW51eC1yZW1vdGVwcm9jQHZnZXIua2VybmVsLm9yZyIsICJiZTllNGEiXQ== Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by smtp-out-n07.prod.us-east-1.postgun.com with SMTP id 60c8f982e27c0cc77f412c7e (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Tue, 15 Jun 2021 19:03:30 GMT Sender: sidgup=codeaurora.org@mg.codeaurora.org Received: by smtp.codeaurora.org (Postfix, from userid 1001) id E53F6C4360C; Tue, 15 Jun 2021 19:03:28 +0000 (UTC) Received: from [192.168.1.10] (cpe-75-83-25-192.socal.res.rr.com [75.83.25.192]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: sidgup) by smtp.codeaurora.org (Postfix) with ESMTPSA id BED07C4338A; Tue, 15 Jun 2021 19:03:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org BED07C4338A Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; spf=fail smtp.mailfrom=sidgup@codeaurora.org Subject: Re: [PATCH v3 1/4] remoteproc: core: Move cdev add before device add To: Greg KH Cc: bjorn.andersson@linaro.org, ohad@wizery.com, linux-remoteproc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, psodagud@codeaurora.org, stable@vger.kernel.org References: <1623723671-5517-1-git-send-email-sidgup@codeaurora.org> <1623723671-5517-2-git-send-email-sidgup@codeaurora.org> From: Siddharth Gupta Message-ID: <0a196786-f624-d9bb-8ef9-55c04ed57497@codeaurora.org> Date: Tue, 15 Jun 2021 12:03:26 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-remoteproc@vger.kernel.org On 6/14/2021 9:56 PM, Greg KH wrote: > On Mon, Jun 14, 2021 at 07:21:08PM -0700, Siddharth Gupta wrote: >> When cdev_add is called after device_add has been called there is no >> way for the userspace to know about the addition of a cdev as cdev_add >> itself doesn't trigger a uevent notification, or for the kernel to >> know about the change to devt. This results in two problems: >> - mknod is never called for the cdev and hence no cdev appears on >> devtmpfs. >> - sysfs links to the new cdev are not established. >> >> The cdev needs to be added and devt assigned before device_add() is >> called in order for the relevant sysfs and devtmpfs entries to be >> created and the uevent to be properly populated. > So this means no one ever ran this code on a system that used devtmpfs? > > How was it ever tested? My testing was done with toybox + Android's ueventd ramdisk. As I mentioned in the discussion, the race became evident recently. I will make sure to test all such changes without systemd/ueventd in the future. Thanks, Sid