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=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 CA2C5C43441 for ; Fri, 9 Nov 2018 06:48:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 938B82086C for ; Fri, 9 Nov 2018 06:48:14 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="RFKU9Xi3" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 938B82086C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728240AbeKIQ1V (ORCPT ); Fri, 9 Nov 2018 11:27:21 -0500 Received: from mail-pl1-f196.google.com ([209.85.214.196]:41869 "EHLO mail-pl1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728103AbeKIQ0y (ORCPT ); Fri, 9 Nov 2018 11:26:54 -0500 Received: by mail-pl1-f196.google.com with SMTP id p16-v6so491103plr.8; Thu, 08 Nov 2018 22:47:46 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=7nHh+0TwFk91NgvrGTFF3LoMskhUBh2w9Bte8yUfnA0=; b=RFKU9Xi3Yp7YCfNhsIPTJbv4o0IJi+S7PkI+LmIvqwAiCqyhXrBuvJTmzhM9zlw6Ir WzxkoAcciw+uvyPKITduXMHBhvsTupJxcN/s2NvKHsTRATBH8zBBA9Vf2srHPt2lWxcy 8i9ZVnPWYH7KtnatiNhPgo1rrFBNycRj4kdZT9/fRm+/d8Fi6RXGVwmNfkv2ekkIIIrp HcaO7ewU694DZwZpyRaTq7e5FU/9GaVv81kAXKRWnUp+vV2fxE7LsR33IP6vZGRriDlf MJz4heqFXFfvOv2cymYeo72N7SKRrkafY8hfRAZzC8cwamk5LjbSUoUmuc/mXePCngz7 8CFA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=7nHh+0TwFk91NgvrGTFF3LoMskhUBh2w9Bte8yUfnA0=; b=naiIzg2k+NdBS0cuISi/aAT90bcr9/E+UVrKZq0J8wk4llKF/OzUvH2rJXhEU/yxWZ mna2UUIeHfIJm8jdeak/X/LHaZdvzKbFt0SBTCg1+n+iaufbxRS17kJPow3K2FL9ACeG v923T6TewetSyLCarlY3jZYgRJSCJLSYP3YpzQEm4Vw4mEdJc8IxSUNc2H5B0Z49yYuT wIjTjIWukvFjzS3UdPVNCP0D/MwAhede6+muH0V31hRpL/yvXEvn7Bt02h+TVui+/M9l H1mhn/nmOtzb6C9ViHa1sP3xghFhudMLQR2Qtb13P83KtN4y4uN4FN5OfyYfcaCUhEdA NAyQ== X-Gm-Message-State: AGRZ1gLSClXBQLG8H3O6bCDzYuMZ7IlvlGwijnn8iHfBf0idri5EsyRw +7N3qMxvXCySjq9pQ5tGaX0= X-Google-Smtp-Source: AJdET5cSeg6AziPZlKY+z+eKf99vuS8f1VgEmHYIlkrwMwjNNbVMpEVRlTrUkou86T2d1KP4ZUKAjg== X-Received: by 2002:a17:902:3a5:: with SMTP id d34-v6mr7727657pld.110.1541746065505; Thu, 08 Nov 2018 22:47:45 -0800 (PST) Received: from localhost ([110.70.55.191]) by smtp.gmail.com with ESMTPSA id v20-v6sm11429198pfj.107.2018.11.08.22.47.43 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 08 Nov 2018 22:47:44 -0800 (PST) Date: Fri, 9 Nov 2018 15:47:40 +0900 From: Sergey Senozhatsky To: Daniel Wang Cc: sergey.senozhatsky.work@gmail.com, Petr Mladek , rostedt@goodmis.org, stable@vger.kernel.org, Alexander.Levin@microsoft.com, akpm@linux-foundation.org, byungchul.park@lge.com, dave.hansen@intel.com, hannes@cmpxchg.org, jack@suse.cz, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Mathieu Desnoyers , Mel Gorman , mhocko@kernel.org, pavel@ucw.cz, penguin-kernel@i-love.sakura.ne.jp, peterz@infradead.org, tj@kernel.org, torvalds@linux-foundation.org, vbabka@suse.cz, Cong Wang , Peter Feiner Subject: Re: 4.14 backport request for dbdda842fe96f: "printk: Add console owner and waiter logic to load balance console writes" Message-ID: <20181109064740.GE599@jagdpanzerIV> References: <20181003091400.rgdjpjeaoinnrysx@pathway.suse.cz> <20181003133704.43a58cf5@gandalf.local.home> <20181004074442.GA12879@jagdpanzerIV> <20181004083609.kcziz2ynwi2w7lcm@pathway.suse.cz> <20181004085515.GC12879@jagdpanzerIV> <20181022100952.GA1147@jagdpanzerIV> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (11/01/18 09:05), Daniel Wang wrote: > > Another deadlock scenario could be the following one: > > > > printk() > > console_trylock() > > down_trylock() > > raw_spin_lock_irqsave(&sem->lock, flags) > > > > panic() > > console_flush_on_panic() > > console_trylock() > > raw_spin_lock_irqsave(&sem->lock, flags) // deadlock > > > > There are no patches addressing this one at the moment. And it's > > unclear if you are hitting this scenario. > > I am not sure, but Steven's patches did make the deadlock I saw go away... You certainly can find cases when "busy spin on console_sem owner" logic can reduce some possibilities. But spin_lock(&lock); NMI; spin_lock(&lock); code is still in the kernel. > A little swamped by other things lately but I'll run a test with it. > If it works, would you recommend taking your patch alone Let's first figure out if it works. -ss