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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 84502CD4F2B for ; Fri, 22 Sep 2023 08:02:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Content-Type: Content-Transfer-Encoding:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:From:References:Cc:To:Subject: MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=pnOeVahU35VNupWJ6LlrSmi8kfamOgb0GCNm7BbS6wI=; b=m9McrN64dQAUrZ ET5dDm43pMCwReCF17ie8BinZmFz9GxMpWGlUGnXOd+d19n11OwdS9KTuW6cqhw4ADAxgDlbZcj2p DjLOZzQ3BFhX320Gzyctq1dKnI1Cjxg7F37xdANgoG7+Vr6GAdmHpE98XeDzAvKH/Tfk0ENo0GblF 0rbWgLGwvtH5Kfm34+TOkqAfIiuENBaF/tfcWtZet88QaANSKHmeY1a/BUOYPsyf3N1pYphMfA0uL uLc8s1Ib6NWQAI3bEcqgPJhfgunkLcBeaMQK+OSVMbTIgOARr+Yzi8cWXx3GZTbQri5fWWNykqAtD 8XWIIVPW3aBqlGAy81EA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1qjb7O-008JpS-1O; Fri, 22 Sep 2023 08:02:30 +0000 Received: from desiato.infradead.org ([2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1qjb7M-008Jnk-2M for linux-um@bombadil.infradead.org; Fri, 22 Sep 2023 08:02:28 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=Content-Transfer-Encoding:Content-Type :In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date:Message-ID: Sender:Reply-To:Content-ID:Content-Description; bh=+q6YS+JCStw/X0O8j/UmxtxEKeNp0xVR0fZ+3s/njVs=; b=YQuJnADrJJTtTmOsyWYrMKU4Bm oMb90R+s8ERVflVx/4ojVHSgeJxnF7O4rqX9nlfeixmLrGnnuVpy7hQ7m8SWz53kdAZa76fmYWfHs Zk5O/c4Q8enMOYvqBOfgel8DvglaUP+8UXv3kbVWZ85WC6J6uUxVz5MAQmDKDc2azSum5mPfTWCi+ CaoxPD0QDk0gMXo5hGyBZoJBs2uGOnSNem3KTWeZxzZrPoLJgZM5J3itBSUDPttG++3nhkifcZnFq pRCv1zvtU8vEPJ6BNOx7DU7I32qQaaacvvyhusm9JrfmWLk0aPQPqgea8ndGBHK6GgPXXq2IMZT+L wCjCxJ2A==; Received: from ns1.kot-begemot.co.uk ([217.160.28.25] helo=www.kot-begemot.co.uk) by desiato.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1qjb7C-00G8ZY-2Z for linux-um@lists.infradead.org; Fri, 22 Sep 2023 08:02:27 +0000 Received: from [192.168.17.6] (helo=jain.kot-begemot.co.uk) by www.kot-begemot.co.uk with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1qjb6s-002bAa-19; Fri, 22 Sep 2023 08:01:58 +0000 Received: from jain.kot-begemot.co.uk ([192.168.3.3]) by jain.kot-begemot.co.uk with esmtp (Exim 4.94.2) (envelope-from ) id 1qjb6p-0026ha-9K; Fri, 22 Sep 2023 09:01:57 +0100 Message-ID: <28f0be57-829b-9ddf-7b0d-a6c84932cbda@cambridgegreys.com> Date: Fri, 22 Sep 2023 09:01:54 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.10.0 Subject: Re: [PATCH v5] um: Enable preemption in UML Content-Language: en-US To: Johannes Berg , linux-um@lists.infradead.org Cc: richard@nod.at References: <20230922065212.484385-1-anton.ivanov@cambridgegreys.com> <2de07f54b33dc060b75d982d4d8189f12e0d4c45.camel@sipsolutions.net> From: Anton Ivanov In-Reply-To: <2de07f54b33dc060b75d982d4d8189f12e0d4c45.camel@sipsolutions.net> X-Clacks-Overhead: GNU Terry Pratchett X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230922_090220_491556_E73322FC X-CRM114-Status: GOOD ( 17.32 ) X-BeenThere: linux-um@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-um" Errors-To: linux-um-bounces+linux-um=archiver.kernel.org@lists.infradead.org On 22/09/2023 08:40, Johannes Berg wrote: > On Fri, 2023-09-22 at 08:38 +0100, Anton Ivanov wrote: >>> I had enabled CONFIG_DEBUG_ATOMIC_SLEEP because that's actually >>> something I'd really like to have in our testing. >>> >>> But with that issue I don't even know how we get there really. It >>> doesn't even happen every time we fork? >>> >>> I'll dig a little bit, but did you try enabling >>> CONFIG_DEBUG_ATOMIC_SLEEP also? >> Will do. I have no crashes over here so I need to trigger this one first. >> >> Though, frankly, if it is a race in a tlb flush it may be subject to local conditions. So it will be difficult to reproduce. >> > Yes, it might be a race in the fork handler maybe? IOW, whenever we > actually do fork, it depends on what conditions the rest is in? I'm not > sure I fully figured out right now how the fork handler is doing all > this, but I sent my mail before I could since you were discussing :) > > But it shouldn't be impossible - while I don't see it for every fork, it > does happen 8 or 9 times in a very simple test that just boots, pings a > bit, and then shuts down, so ... My favorite test which I run on all changes is: find /usr -type f -exec cat {} > /dev/null \; On Debian this forks /bin/cat for each file and does IO on it. That test passes here every time :( However, I did not have debug turned on. So, I would not be surprised if something in the debug portion of the config makes the crashes more likely. Otherwise, each fork is a forced tlb_flush_all, so it is a massive tlb exercise. Any bugs, locking, etc are likely to show up. > > johannes > -- Anton R. Ivanov Cambridgegreys Limited. Registered in England. Company Number 10273661 https://www.cambridgegreys.com/ _______________________________________________ linux-um mailing list linux-um@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-um