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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 65A90EB64DD for ; Wed, 5 Jul 2023 08:58:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231851AbjGEI6G (ORCPT ); Wed, 5 Jul 2023 04:58:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37476 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229776AbjGEI6D (ORCPT ); Wed, 5 Jul 2023 04:58:03 -0400 Received: from mail-lj1-x22c.google.com (mail-lj1-x22c.google.com [IPv6:2a00:1450:4864:20::22c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5465010E2 for ; Wed, 5 Jul 2023 01:58:02 -0700 (PDT) Received: by mail-lj1-x22c.google.com with SMTP id 38308e7fff4ca-2b6a675743dso98857441fa.2 for ; Wed, 05 Jul 2023 01:58:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1688547480; x=1691139480; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=9ooezHDISTP5WoI5HS8olj7QDU0KGHHznlF81+KKRE8=; b=D9oW1xTf7E2yR2lfWEkBLxQIxeRX5NbGf+W+mwDpumZSGHlgUzAYw2E9JDFQ76Gz4b Nqgocvgbdi0W2FS7g103lv8St7rSKonWGjTnnNJJSquoHazZr8364aksiBzWU52/Lgts gyqjIfSZPRdQ7CE/oR3UYkr8SYKPm4devgUNFx/A5MMZ3zkRSJfhRypvkV8eUgIikfbm 3w1G0nGZEwJP1s3Y1ovJu1aPtvLY+ms4dAbVv0p9AFngiLE+oD0S67rYZiId+R/q7yHx UKUmjmkETZdczJ1xbX60oWshNi3KFel1qUcqjU6cFUJu6MltsHfAQQejRRj9JygzSy6U 6xCw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1688547480; x=1691139480; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=9ooezHDISTP5WoI5HS8olj7QDU0KGHHznlF81+KKRE8=; b=J2Wu7PRNY1T2yBqk4ETOy279NlDJxPjTRYJu0sX5DCt5XDwk3qa38zae8BuJSqPDRc /AHvLsCS7mQb2Ey64nmkVQYqHLBAd/5CKUQ6lhGVWRO+YzGxFlY31KtQCrJ0ybgOxbLV TrAoh7lxiBmPsYSWuKFTNQHNg5ABC+YxUlKB1QuVPXPVdiIKbKz2SNYid9PIkP5SbOTF Gdl4eDkR4V2tOytQNRbWoVTwWA4meZ0X7ok1JVi9dkfvga+K1/iAa8JmuA8RKNOB6IsK 0Oez8/MXFeHXDsldjzXjwnMvHFLnT88EA91WazkpDPp+nK70JZCCTrOAFDgAqZZXe1XX TTtg== X-Gm-Message-State: ABy/qLZkCWaA2Lo+pfffrtEm0wANM74kC4nr/zTTk7T+VltUYiD5D8CF /t9zulFot/B1ZYsgWtGhBU3SRSwEJx/FypvRA5o= X-Google-Smtp-Source: APBJJlFc17+4kniCtz+9dI4BXaX2+imC7dTdNItgNsm1bEK4fLRo3BnS/Cf8ScHAvr2uxbVirMO2eg== X-Received: by 2002:a2e:991a:0:b0:2b6:e332:d089 with SMTP id v26-20020a2e991a000000b002b6e332d089mr8444815lji.41.1688547480509; Wed, 05 Jul 2023 01:58:00 -0700 (PDT) Received: from [192.168.1.20] ([178.197.219.26]) by smtp.gmail.com with ESMTPSA id s21-20020a170906455500b00992b7ff3993sm7841810ejq.126.2023.07.05.01.57.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 05 Jul 2023 01:58:00 -0700 (PDT) Message-ID: Date: Wed, 5 Jul 2023 10:57:58 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.12.0 Subject: Re: [PATCH v2] watchdog: s3c2410: Fix potential deadlock on &wdt->lock Content-Language: en-US To: Chengfeng Ye , alim.akhtar@samsung.com, wim@linux-watchdog.org, linux@roeck-us.net Cc: linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-watchdog@vger.kernel.org, linux-kernel@vger.kernel.org References: <20230705072304.37741-1-dg573847474@gmail.com> From: Krzysztof Kozlowski In-Reply-To: <20230705072304.37741-1-dg573847474@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/07/2023 09:23, Chengfeng Ye wrote: > As &wdt->lock is acquired by hard irq s3c2410wdt_irq(), other > acquisition of the same lock under process context should > disable irq, otherwise deadlock could happen if the irq preempt > the execution while the lock is held in process context on the > same CPU. > > [Deadlock Scenario] > s3c2410wdt_suspend() > -> s3c2410wdt_stop() > -> spin_lock(&wdt->lock) > > -> s3c2410wdt_irq() > -> s3c2410wdt_keepalive() > -> spin_lock(&wdt->lock) (deadlock here) > > [Deadlock Scenario] > s3c2410wdt_probe() > -> s3c2410wdt_start() > -> spin_lock(&wdt->lock) > > -> s3c2410wdt_irq() > -> s3c2410wdt_keepalive() > -> spin_lock(&wdt->lock) (deadlock here) > > This flaw was found by an experimental static analysis tool I am > developing for irq-related deadlock, which reported the above > warning when analyzing the linux kernel 6.4-rc7 release. > > The tentative patch fix the potential deadlock by spin_lock_irqsave() > under process context. > > Signed-off-by: Chengfeng Ye > --- > drivers/watchdog/s3c2410_wdt.c | 10 ++++++---- > 1 file changed, 6 insertions(+), 4 deletions(-) > > diff --git a/drivers/watchdog/s3c2410_wdt.c b/drivers/watchdog/s3c2410_wdt.c > index 95416a9bdd4b..2dfc0d6a3004 100644 > --- a/drivers/watchdog/s3c2410_wdt.c > +++ b/drivers/watchdog/s3c2410_wdt.c > @@ -399,10 +399,11 @@ static void __s3c2410wdt_stop(struct s3c2410_wdt *wdt) Why you didn't update also s3c2410wdt_keepalive()? Best regards, Krzysztof