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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_2 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 24EEAC3A5A9 for ; Wed, 4 Sep 2019 12:14:28 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id DF0D62339E for ; Wed, 4 Sep 2019 12:14:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=lca.pw header.i=@lca.pw header.b="QnuouqMm" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DF0D62339E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lca.pw Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 7F8F86B0003; Wed, 4 Sep 2019 08:14:27 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7A82E6B0006; Wed, 4 Sep 2019 08:14:27 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 670A96B0007; Wed, 4 Sep 2019 08:14:27 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0148.hostedemail.com [216.40.44.148]) by kanga.kvack.org (Postfix) with ESMTP id 3ECC06B0003 for ; Wed, 4 Sep 2019 08:14:27 -0400 (EDT) Received: from smtpin08.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with SMTP id 9BA07181AC9B6 for ; Wed, 4 Sep 2019 12:14:26 +0000 (UTC) X-FDA: 75897130932.08.door90_26bb1ec03781d X-HE-Tag: door90_26bb1ec03781d X-Filterd-Recvd-Size: 5104 Received: from mail-qt1-f193.google.com (mail-qt1-f193.google.com [209.85.160.193]) by imf01.hostedemail.com (Postfix) with ESMTP for ; Wed, 4 Sep 2019 12:14:26 +0000 (UTC) Received: by mail-qt1-f193.google.com with SMTP id l22so11811469qtp.10 for ; Wed, 04 Sep 2019 05:14:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=lca.pw; s=google; h=message-id:subject:from:to:cc:date:in-reply-to:references :mime-version:content-transfer-encoding; bh=bl6KGDbxyH9xibYLFzb2mGM47IhCp8dCBtbeKfHElvA=; b=QnuouqMmL8Ruk+R6jgbyEXsFKtEUI5jAhWEUccMzoIFT3hIMpBl5QgvXmfPajbeZgi d2iMXBHvzXkhD7THAH6LnGOC8s/EcsqTzcVeAI3UnGtcjpKZGJt9NPTdmm5cTcnuw2XO N7Hi3qrBbJdk3+mwG9Milp6EEDXrhwxY1Uvt0wOyxopI4PH9pLEML/64jmM/Ls+0o47e ktXGLGHcIC5QGyLUWDJb1dIU4+DiP5SK1Z8QCMsBF1GWBujQzoXO1C5jS6EoUMD6kApL qjrI+wfMsyPkw9IUz1frp0Vpe+I20t/JM75jAVRP8cFXMe71o4zxTvut7gNWwNvoMf5a NXkw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:message-id:subject:from:to:cc:date:in-reply-to :references:mime-version:content-transfer-encoding; bh=bl6KGDbxyH9xibYLFzb2mGM47IhCp8dCBtbeKfHElvA=; b=SJGZVUE5XaJSOX1hgGFJZCRfWUXkM+AR+SbxLVa56HT7FHcTANmOP7gFTZLgO3qZGX ZH5RtnLqBBXtYSL6s+IS/y4AV4fpp7oA89mnYPUTMN7vyBbtRU5l5riyAdYX1odjNkS0 RjGN/Qb0C98IaAt1MIZ4S5zh9Fb7qilBvZuVVAE5+K0fsro3Fbtwk3WJw9yfC8lDXXjQ Vh+JwtZZ51BnRjMFOdHMjSqWy1oJ5q9JffUKpX6ccAb4FOJqFi00WSN/L1JyO5CvZz6f EfzqNVboo8ul6zqX6PvkIvjCybku9fm8K3fRFH2tdwr1eRPc535Jdco7ahrZuIAXu0hP NOHA== X-Gm-Message-State: APjAAAUJ+cUL5yuGnIWzan7KWvd6slM4ZIUQI9Cy5X2JFfqJzRykwiQO fssZeFXv0BhkakB8scDvx6Qb2A6j3uY= X-Google-Smtp-Source: APXvYqwVMedOXPfbW97QL3Tml18XfuCAjaFmLYqEjgyl13jtOyVoXSys9SE3TEG9CouaQn2bE7sZGw== X-Received: by 2002:a0c:8ad0:: with SMTP id 16mr14055557qvw.237.1567599265215; Wed, 04 Sep 2019 05:14:25 -0700 (PDT) Received: from dhcp-41-57.bos.redhat.com (nat-pool-bos-t.redhat.com. [66.187.233.206]) by smtp.gmail.com with ESMTPSA id 29sm7794713qkp.86.2019.09.04.05.14.23 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 04 Sep 2019 05:14:24 -0700 (PDT) Message-ID: <1567599263.5576.72.camel@lca.pw> Subject: Re: [PATCH] net/skbuff: silence warnings under memory pressure From: Qian Cai To: Sergey Senozhatsky , Michal Hocko Cc: Eric Dumazet , davem@davemloft.net, netdev@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Petr Mladek , Sergey Senozhatsky , Steven Rostedt Date: Wed, 04 Sep 2019 08:14:23 -0400 In-Reply-To: <20190904074312.GA25744@jagdpanzerIV> References: <1567178728.5576.32.camel@lca.pw> <229ebc3b-1c7e-474f-36f9-0fa603b889fb@gmail.com> <20190903132231.GC18939@dhcp22.suse.cz> <1567525342.5576.60.camel@lca.pw> <20190903185305.GA14028@dhcp22.suse.cz> <1567546948.5576.68.camel@lca.pw> <20190904061501.GB3838@dhcp22.suse.cz> <20190904064144.GA5487@jagdpanzerIV> <20190904065455.GE3838@dhcp22.suse.cz> <20190904071911.GB11968@jagdpanzerIV> <20190904074312.GA25744@jagdpanzerIV> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6 (3.22.6-10.el7) Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, 2019-09-04 at 16:43 +0900, Sergey Senozhatsky wrote: > On (09/04/19 16:19), Sergey Senozhatsky wrote: > > Hmm. I need to look at this more... wake_up_klogd() queues work only = once > > on particular CPU: irq_work_queue(this_cpu_ptr(&wake_up_klogd_work)); > >=20 > > bool irq_work_queue() > > { > > /* Only queue if not already pending */ > > if (!irq_work_claim(work)) > > return false; > >=20 > > __irq_work_queue_local(work); > > } >=20 > Plus one more check - waitqueue_active(&log_wait). printk() adds > pending irq_work only if there is a user-space process sleeping on > log_wait and irq_work is not already scheduled. If the syslog is > active or there is noone to wakeup then we don't queue irq_work. Another possibility for this potential livelock is that those printk() fr= om warn_alloc(), dump_stack() and show_mem() increase the time it needs to p= rocess build_skb() allocation failures significantly under memory pressure. As t= he result, ksoftirqd() could be rescheduled during that time via a different= CPU (this is a large x86 NUMA system anyway), [83605.577256][=C2=A0=C2=A0=C2=A0C31]=C2=A0=C2=A0run_ksoftirqd+0x1f/0x40 [83605.577256][=C2=A0=C2=A0=C2=A0C31]=C2=A0=C2=A0smpboot_thread_fn+0x255/= 0x440 [83605.577256][=C2=A0=C2=A0=C2=A0C31]=C2=A0=C2=A0kthread+0x1df/0x200 [83605.577256][=C2=A0=C2=A0=C2=A0C31]=C2=A0=C2=A0ret_from_fork+0x35/0x40 In addition, those printk() will deal with console drivers or even a netw= orking console, so it is probably not unusual that it could call irq_exit()- >__do_softirq() at one point and then this livelock.