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=-6.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 68D8CC433E0 for ; Mon, 27 Jul 2020 15:42:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 408C1206E7 for ; Mon, 27 Jul 2020 15:42:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=broadcom.com header.i=@broadcom.com header.b="N64yA6en" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730938AbgG0Pmm (ORCPT ); Mon, 27 Jul 2020 11:42:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49924 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730527AbgG0Pml (ORCPT ); Mon, 27 Jul 2020 11:42:41 -0400 Received: from mail-wm1-x344.google.com (mail-wm1-x344.google.com [IPv6:2a00:1450:4864:20::344]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 165A1C0619D2 for ; Mon, 27 Jul 2020 08:42:41 -0700 (PDT) Received: by mail-wm1-x344.google.com with SMTP id p14so14231065wmg.1 for ; Mon, 27 Jul 2020 08:42:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=broadcom.com; s=google; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=q30VrVY5X0HHdrGzlOgbzohfZx9h3nY4CKObZ9uief0=; b=N64yA6enn2h2KhVpllPNrEdDz0RrQ7jqd01zk5ciCF9VgY1wF6gi8LNAggzubBmIfk 4uGhhEPE2QX/cY7tKM+QCjTPoj/KkOGBlDnJ8TiZHV/gEKNVAlTmgNsfoNvQZPhbpaVK OiOAEVmyXwW432/bO8bsIg67ZINiqTIrjqc9k= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=q30VrVY5X0HHdrGzlOgbzohfZx9h3nY4CKObZ9uief0=; b=GRbTQ1qhJS27CKQEOujqjJ0k43ptysNekBlawHUmeFHkyn+14vbLvbRGGsN1JdeVol F3zaqcSrF73qJPjxHY1HDCb1Vpqg/2qUXwfrook6/C0/jxhx8Fa/jPp9IfG5HV4453bU 9Npx84fVYHMrU+YTl+vHG1WxAdGHBu9AUEhiPTu/lS91YqwKddaSzjLfjLjgsE4ZXIuD RiXIh4tnMm8B/yZ7fU4fAbp6EyJvUIb1Y8hytbvWUn24fAeJPvnycWoSt1bJo9nIeAM+ dIjsO/vhbF2BdZhu2c6wShD3K1Zpu8MF4naa9AoerqoONJcnNcj/JEMuqbzOYvNasj7t YT1A== X-Gm-Message-State: AOAM533cljfLULn9J5ggcSAgU4l8Tfv7H7rGyarcweXb9lB4Xd8HfQq6 r5HhH3Dd5TyF6SiBjQVCX6+SGBDFkKhLin1F X-Google-Smtp-Source: ABdhPJw2AFsLQ3QfoNPjcQVXUMOo94VGbLrWaNX6UgSpcDfrl2zhz/5cV8jTG+eKSfbeiAD3UuccXA== X-Received: by 2002:a1c:9914:: with SMTP id b20mr20577167wme.15.1595864559486; Mon, 27 Jul 2020 08:42:39 -0700 (PDT) Received: from [10.136.8.246] ([192.19.228.250]) by smtp.gmail.com with ESMTPSA id c25sm1318wml.18.2020.07.27.08.42.37 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 27 Jul 2020 08:42:38 -0700 (PDT) Subject: Re: [PATCH] i2c: iproc: fix race between client unreg and isr To: Wolfram Sang Cc: Dhananjay Phadke , Rayagonda Kokatanur , linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org, Ray Jui , bcm-kernel-feedback-list@broadcom.com References: <1595115599-100054-1-git-send-email-dphadke@linux.microsoft.com> <116ac90c-8b49-ca89-90a4-9a28f43a7c50@broadcom.com> <20200722104128.GK1030@ninjato> <5048cf44-e2c2-ee31-a9fb-b823f16c2c7d@broadcom.com> <20200725101815.GA1519@ninjato> From: Ray Jui Message-ID: <4cf12c92-889d-ffbf-f8de-c1e08cfb8ce9@broadcom.com> Date: Mon, 27 Jul 2020 08:42:33 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200725101815.GA1519@ninjato> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Wolfram, On 7/25/2020 3:18 AM, Wolfram Sang wrote: > >> I think the following sequence needs to be implemented to make this >> safe, i.e., after 'synchronize_irq', no further slave interrupt will be >> fired. >> >> In 'bcm_iproc_i2c_unreg_slave': >> >> 1. Set an atomic variable 'unreg_slave' (I'm bad in names so please come >> up with a better name than this) >> >> 2. Disable all slave interrupts >> >> 3. synchronize_irq >> >> 4. Set slave to NULL >> >> 5. Erase slave addresses > > What about this in unreg_slave? > > 1. disable_irq() > This includes synchronize_irq() and avoids the race. Because irq > will be masked at interrupt controller level, interrupts coming > in at the I2C IP core level should still be pending once we > reenable the irq. > Can you confirm that even if we have irq pending at the i2c IP core level, as long as we execute Step 2. below (to disable/mask all slave interrupts), after 'enable_irq' is called, we still will not receive any further i2c slave interrupt? Basically I'm asking if interrupts will be "cached" at the GIC controller level after 'disable_irq' is called. As long as that is not the case, then I think we are good. The goal of course is to ensure there's no further slave interrupts after 'enable_irq' in Step 3 below. Thanks! > 2. disable all slave interrupts > > 3. enable_irq() > > 4. clean up the rest (pointer, address) > > Or am I overlooking something? >