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=-8.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_PASS,USER_IN_DEF_DKIM_WL 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 0D43AC0044C for ; Thu, 1 Nov 2018 16:05:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 80489205F4 for ; Thu, 1 Nov 2018 16:05:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="r130sYIV" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 80489205F4 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.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 S1729060AbeKBBJQ (ORCPT ); Thu, 1 Nov 2018 21:09:16 -0400 Received: from mail-it1-f194.google.com ([209.85.166.194]:35818 "EHLO mail-it1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728678AbeKBBJQ (ORCPT ); Thu, 1 Nov 2018 21:09:16 -0400 Received: by mail-it1-f194.google.com with SMTP id p64-v6so2723643itp.0 for ; Thu, 01 Nov 2018 09:05:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=SCd4CW0jvlSppGdK5PCNzM6flSTfHlFMcsrJ8NnvzCE=; b=r130sYIVOLkRAvwA6ftbBDlJ+c9Tk88CQZuge83rvdFTC5cTOuRe0iyOzQAstC1B0I RK/YpnwoH9DExSh4T+BvclzurV2uohDKVG7KB2MLr51o4rUyvK2zOHxLF4yD//QSm+YO Ij+EpdTG9UmX5yFTNOaJRMHy+1GDx2TQYT69WBJ9iatJD88YoWu6wqRcpklTFzojL8kF kN60X6v5q0EgfkVinwEvJPBlZtR0JZgDeRGBhCfh9DU9qO1G9W0O5cMgL+3jWtLOZ4bx mCF9C+Yw4GXUMmDdkqQXcC6JFHl/55lQjGSP2+zQlOZcwlolLeDqz9LmtRn+vri1qD2s 9MMQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=SCd4CW0jvlSppGdK5PCNzM6flSTfHlFMcsrJ8NnvzCE=; b=Dku1j3hRzGavUegbRfpEy0ngk9Fk7IYu36aaivTtpUJ0NGdUno7QSHEPa81EFUCJIe Ab/DGZ+StaTsnwrknbN6HCAG1SvhUAaAZxZpkfWcfleKvSrG4Hw3mXX1zh2uHWsLCrFT f4DCVuFtbbC0pjRCq1qBIpXjrLm/A7g4tDItwln4KIOHtSvcdA+3GqVytYsAKmjrwtu9 wq6qOoog+oDKMZ/0RGZss4BfLKtAYPxzj7/ZUl7uvP32oWMtXTXCWOogrjINLyI+fVYZ Y+sVraoex+0zpQn1uR25kK+ivBKrnoDJ4ntfPktjbhJ+TNhbpZLhBk859O4+d/OwE+aC AO1g== X-Gm-Message-State: AGRZ1gI3pf93AgI1VDTm3sJba7AiU3+FMnipEVHgSU6RqucmW6bDncH3 nKkqO6VNpci9JS4nb68FIDtnHuDtr9f/eFbvnBDrJg== X-Google-Smtp-Source: AJdET5c5OOMmjbazqs69A3CqGAkXb7UspTvw4wpw3YA+8TOAJ6+InEUNR75KgU2VMtH9rbIf637I/LV1JhBgokIbTy4= X-Received: by 2002:a24:7406:: with SMTP id o6-v6mr6119688itc.81.1541088339345; Thu, 01 Nov 2018 09:05:39 -0700 (PDT) MIME-Version: 1.0 References: <20181002212327.7aab0b79@vmware.local.home> <20181003091400.rgdjpjeaoinnrysx@pathway.suse.cz> <20181003133704.43a58cf5@gandalf.local.home> <20181004074442.GA12879@jagdpanzerIV> <20181004083609.kcziz2ynwi2w7lcm@pathway.suse.cz> <20181004085515.GC12879@jagdpanzerIV> <20181022100952.GA1147@jagdpanzerIV> In-Reply-To: <20181022100952.GA1147@jagdpanzerIV> From: Daniel Wang Date: Thu, 1 Nov 2018 09:05:27 -0700 Message-ID: Subject: Re: 4.14 backport request for dbdda842fe96f: "printk: Add console owner and waiter logic to load balance console writes" To: sergey.senozhatsky.work@gmail.com Cc: 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 Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-256; boundary="0000000000001a71ef05799c97a9" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --0000000000001a71ef05799c97a9 Content-Type: text/plain; charset="UTF-8" On Mon, Oct 22, 2018 at 3:10 AM Sergey Senozhatsky 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... > > > > I see that Sergey had sent an RFC series for similar things. Are those > > trying to solve the deadlock problem in a different way? > > Umm, I wouldn't call it "another way". It turns non-reentrant serial > consoles to re-entrable ones. Did you test patch [1] from that series > on you environment, by the way? 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 and not bother taking Steven's (since as you mentioned above even with his patches there's still possibility for other deadlocks) ? > > [1] lkml.kernel.org/r/20181016050428.17966-2-sergey.senozhatsky@gmail.com > > -ss -- Best, Daniel --0000000000001a71ef05799c97a9 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIIS7QYJKoZIhvcNAQcCoIIS3jCCEtoCAQExDzANBglghkgBZQMEAgEFADALBgkqhkiG9w0BBwGg ghBTMIIEXDCCA0SgAwIBAgIOSBtqDm4P/739RPqw/wcwDQYJKoZIhvcNAQELBQAwZDELMAkGA1UE BhMCQkUxGTAXBgNVBAoTEEdsb2JhbFNpZ24gbnYtc2ExOjA4BgNVBAMTMUdsb2JhbFNpZ24gUGVy c29uYWxTaWduIFBhcnRuZXJzIENBIC0gU0hBMjU2IC0gRzIwHhcNMTYwNjE1MDAwMDAwWhcNMjEw NjE1MDAwMDAwWjBMMQswCQYDVQQGEwJCRTEZMBcGA1UEChMQR2xvYmFsU2lnbiBudi1zYTEiMCAG A1UEAxMZR2xvYmFsU2lnbiBIViBTL01JTUUgQ0EgMTCCASIwDQYJKoZIhvcNAQEBBQADggEPADCC 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