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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,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 B4D0EC47404 for ; Wed, 9 Oct 2019 13:51:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8826B21835 for ; Wed, 9 Oct 2019 13:51:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570629119; bh=UNc/8F9d9S64kVqPjtUhAd+6LIUympZdKfhz72oz8B4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=Nm6g9XKtfpXBnDD3et44mQfygk4iR8l73I0lGdLCWb77z3FTyv3QNi2Z4mxflID/a 7IvN0Qi9Ycm9GKyHJOBN4qL1HoLv9f0oi5NV8IJjnSCzuNcIETmT+EyWSGASy7KNre 7dQRZtgqUdMCPxV5q65YatMU9y4MGpP/6nC4d/YM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731315AbfJINv6 (ORCPT ); Wed, 9 Oct 2019 09:51:58 -0400 Received: from mx2.suse.de ([195.135.220.15]:39914 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729883AbfJINv6 (ORCPT ); Wed, 9 Oct 2019 09:51:58 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 287BDAF6B; Wed, 9 Oct 2019 13:51:56 +0000 (UTC) Date: Wed, 9 Oct 2019 15:51:55 +0200 From: Michal Hocko To: Qian Cai Cc: Petr Mladek , Christian Borntraeger , Heiko Carstens , sergey.senozhatsky.work@gmail.com, rostedt@goodmis.org, peterz@infradead.org, linux-mm@kvack.org, john.ogness@linutronix.de, akpm@linux-foundation.org, Vasily Gorbik , Peter Oberparleiter , david@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] mm/page_isolation: fix a deadlock with printk() Message-ID: <20191009135155.GC6681@dhcp22.suse.cz> References: <1570550917.5576.303.camel@lca.pw> <20191008183525.GQ6681@dhcp22.suse.cz> <1570561573.5576.307.camel@lca.pw> <20191008191728.GS6681@dhcp22.suse.cz> <1570563324.5576.309.camel@lca.pw> <20191009114903.aa6j6sa56z2cssom@pathway.suse.cz> <1570626402.5937.1.camel@lca.pw> <20191009132746.GA6681@dhcp22.suse.cz> <1570628593.5937.3.camel@lca.pw> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1570628593.5937.3.camel@lca.pw> 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 Wed 09-10-19 09:43:13, Qian Cai wrote: > On Wed, 2019-10-09 at 15:27 +0200, Michal Hocko wrote: > > On Wed 09-10-19 09:06:42, Qian Cai wrote: > > [...] > > > https://lore.kernel.org/linux-mm/1570460350.5576.290.camel@lca.pw/ > > > > > > [  297.425964] -> #1 (&port_lock_key){-.-.}: > > > [  297.425967]        __lock_acquire+0x5b3/0xb40 > > > [  297.425967]        lock_acquire+0x126/0x280 > > > [  297.425968]        _raw_spin_lock_irqsave+0x3a/0x50 > > > [  297.425969]        serial8250_console_write+0x3e4/0x450 > > > [  297.425970]        univ8250_console_write+0x4b/0x60 > > > [  297.425970]        console_unlock+0x501/0x750 > > > [  297.425971]        vprintk_emit+0x10d/0x340 > > > [  297.425972]        vprintk_default+0x1f/0x30 > > > [  297.425972]        vprintk_func+0x44/0xd4 > > > [  297.425973]        printk+0x9f/0xc5 > > > [  297.425974]        register_console+0x39c/0x520 > > > [  297.425975]        univ8250_console_init+0x23/0x2d > > > [  297.425975]        console_init+0x338/0x4cd > > > [  297.425976]        start_kernel+0x534/0x724 > > > [  297.425977]        x86_64_start_reservations+0x24/0x26 > > > [  297.425977]        x86_64_start_kernel+0xf4/0xfb > > > [  297.425978]        secondary_startup_64+0xb6/0xc0 > > > > > > where the report again show the early boot call trace for the locking > > > dependency, > > > > > > console_owner --> port_lock_key > > > > > > but that dependency clearly not only happen in the early boot. > > > > Can you provide an example of the runtime dependency without any early > > boot artifacts? Because this discussion really doens't make much sense > > without a clear example of a _real_ lockdep report that is not a false > > possitive. All of them so far have been concluded to be false possitive > > AFAIU. > > An obvious one is in the above link. Just replace the trace in #1 above with > printk() from anywhere, i.e., just ignore the early boot calls there as they are > not important. > > printk() > console_unlock() > console_lock_spinning_enable() --> console_owner_lock > call_console_drivers() > serial8250_console_write() --> port->lock Can you paste the full lock chain graph to be sure we are on the same page? -- Michal Hocko SUSE Labs