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 2A3FFC2BA4C for ; Wed, 26 Jan 2022 15:31:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242845AbiAZPbW (ORCPT ); Wed, 26 Jan 2022 10:31:22 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45462 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242823AbiAZPbV (ORCPT ); Wed, 26 Jan 2022 10:31:21 -0500 Received: from mail-qk1-x730.google.com (mail-qk1-x730.google.com [IPv6:2607:f8b0:4864:20::730]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 73253C06161C for ; Wed, 26 Jan 2022 07:31:21 -0800 (PST) Received: by mail-qk1-x730.google.com with SMTP id s12so28573774qkg.6 for ; Wed, 26 Jan 2022 07:31:21 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=sender:date:from:to:cc:subject:message-id:reply-to:references :mime-version:content-disposition:in-reply-to; bh=tuAwDuCZNYp0iGAO00ew96R+E+k/Li3kJqdbAoMlqDA=; b=XxiKAfF2rgXWe+VtsLPZa3DK5VCtxOwZz0P3m2tkGRvpJaozAGvhVyPYH3FqjY/KfD puonl2ptqCydJBcgXQ9om7ictAVEYT6OJy5wSDk1r4uGnSyvoV8sEurxQQD3AI1untmQ zgr/z0IbMslz7n48hWdWUaKExe6iNxZQevWSP2j0bxFWBkf5FoRuneeOiWWLEQc/qokr HRQd6wVFl2J1O5Dj6hWYav6KyE7SniLNMKIZAubuV38tnfLCQjdLFbx0f5zXpbhXpN0I 3ZarIuzDY6MB/Fu709JZ0gcsXtj26kl5S9dEz9vvt4/mAbpnM65VQEFNqSKXOou/uTBn avvg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :reply-to:references:mime-version:content-disposition:in-reply-to; bh=tuAwDuCZNYp0iGAO00ew96R+E+k/Li3kJqdbAoMlqDA=; b=73R2jboxraTg4mUxvPK8UtJAJCDZvWVv5NF3QJ7tAgi1wsJzilbpKT0fqMoMb8D+53 xfDBs9bLRRgNoOVFe3pJvh6DQyjjLfZCp0IMNNvlNtmVyFMgtR3eoL9VMgAf8vfnhQym BCtlf0x+O2Gvh8rh3rKY6oDm2yjnYqL/pqKstsVBxkBTm7peLfIRywKTgV66l+lHfMq2 Xk+1LZ6Cl19x+PFDpvYHgVV/+s4U6TsvMI/okUAP4tOwpipByP8J853Zl9+0cSELr7Rf Iw7SxqckCAXCRx0U/EFUR1rDYFWW1BmDT3yEUt9526P4QJOIQ1syP1lHmIuzYozRXqDk Scng== X-Gm-Message-State: AOAM531/YY9WxbvU2zrjrwKMxNBV0aPK7EVJO3EK6SwbGz8pWP2tElmR FGtGHTFvV0T0PlIQX3V/RA== X-Google-Smtp-Source: ABdhPJzQZYzEQZeKdD3J/ksROYUm394TENDPD0j1YNrEtW7UWPb2URik2SuytfQE2a+4Hk83jC4gbQ== X-Received: by 2002:a37:9c8e:: with SMTP id f136mr13156652qke.575.1643211080472; Wed, 26 Jan 2022 07:31:20 -0800 (PST) Received: from serve.minyard.net ([47.184.144.75]) by smtp.gmail.com with ESMTPSA id e6sm10756255qte.6.2022.01.26.07.31.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 26 Jan 2022 07:31:19 -0800 (PST) Sender: Corey Minyard Received: from minyard.net (unknown [IPv6:2001:470:b8f6:1b:4de2:5f2e:d934:1026]) by serve.minyard.net (Postfix) with ESMTPSA id C85C1180004; Wed, 26 Jan 2022 15:31:18 +0000 (UTC) Date: Wed, 26 Jan 2022 09:31:17 -0600 From: Corey Minyard To: Juergen Gross Cc: Ingo Molnar , "Paul E. McKenney" , LKML Subject: Re: Possible reproduction of CSD locking issue Message-ID: <20220126153117.GU34919@minyard.net> Reply-To: minyard@acm.org References: <20220125182737.GO34919@minyard.net> <4609fe56-7d88-8176-a378-0f465670b37d@suse.com> <20220126135639.GS34919@minyard.net> <70245998-b99e-ebe7-e932-f8a1b46f6ac7@suse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <70245998-b99e-ebe7-e932-f8a1b46f6ac7@suse.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 26, 2022 at 03:51:36PM +0100, Juergen Gross wrote: > On 26.01.22 14:56, Corey Minyard wrote: > > On Wed, Jan 26, 2022 at 07:08:22AM +0100, Juergen Gross wrote: snip.. > > > > csd: cnt(63d8e1f): 0003->0037 queue > > csd: cnt(63d8e20): 0003->0037 ipi > > csd: cnt(63d8e21): 0003->0037 ping > > > > In __smp_call_single_queue_debug CPU 3 sends another message to > > CPU 55 and sends an IPI. But there should be a pinged entry > > after this. > > > > csd: cnt(63d8e22): 0003->0037 queue > > csd: cnt(63d8e23): 0003->0037 noipi > > This is interesting. Those are 5 consecutive entries without any > missing in between (see the counter values). Could it be that after > the ping there was an interrupt and the code was re-entered for > sending another IPI? This would clearly result in a hang as seen. Since preempt is enabled, wouldn't it eventually come back to the first thread and send the IPI? Unless CPU 3 is stuck in an interrupt or interrupt storm. -corey