From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io1-f69.google.com (mail-io1-f69.google.com [209.85.166.69]) by kanga.kvack.org (Postfix) with ESMTP id D70176B0006 for ; Tue, 2 Oct 2018 13:21:52 -0400 (EDT) Received: by mail-io1-f69.google.com with SMTP id s15-v6so2997070iob.11 for ; Tue, 02 Oct 2018 10:21:52 -0700 (PDT) Received: from mail-sor-f41.google.com (mail-sor-f41.google.com. [209.85.220.41]) by mx.google.com with SMTPS id z189-v6sor7825465itd.16.2018.10.02.10.21.51 for (Google Transport Security); Tue, 02 Oct 2018 10:21:51 -0700 (PDT) MIME-Version: 1.0 References: <20180927194601.207765-1-wonderfly@google.com> <20181001152324.72a20bea@gandalf.local.home> <20181002084225.6z2b74qem3mywukx@pathway.suse.cz> In-Reply-To: <20181002084225.6z2b74qem3mywukx@pathway.suse.cz> From: Daniel Wang Date: Tue, 2 Oct 2018 10:21:39 -0700 Message-ID: Subject: Re: 4.14 backport request for dbdda842fe96f: "printk: Add console owner and waiter logic to load balance console writes" Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-256; boundary="00000000000055478705774228ad" Sender: owner-linux-mm@kvack.org List-ID: To: Petr Mladek Cc: 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 --00000000000055478705774228ad Content-Type: text/plain; charset="UTF-8" On Tue, Oct 2, 2018 at 1:42 AM Petr Mladek wrote: > Well, I still wonder why it helped and why you do not see it with 4.4. > I have a feeling that the console owner switch helped only by chance. So do I. I don't think Steven had the deadlock in mind when working on that patch, but with that patch and that patch alone, the deadlock disappeared. > In fact, you might be affected by a race in > printk_safe_flush_on_panic() that was fixed by the commit: > > 554755be08fba31c7 printk: drop in_nmi check from printk_safe_flush_on_panic() > > The above one commit might be enough. Well, there was one more Thanks for the pointer. Let me test this out. > NMI-related race that was fixed by: > > ba552399954dde1b printk: Split the code for storing a message into the log buffer > a338f84dc196f44b printk: Create helper function to queue deferred console handling > 03fc7f9c99c1e7ae printk/nmi: Prevent deadlock when accessing the main log buffer in NMI > > Best Regards, > Petr On Tue, Oct 2, 2018 at 1:17 AM Sergey Senozhatsky wrote: > Sorry, I'm missing something here. Steven's patch deals with lockups and > I understand why you want to backport the patch set; but console output > deadlock on panic() is another thing. Understood. But it did fix the deadlock for me and without it I hit the deadlock pretty consistently. Let me test the patch Petr pointed out and will update here. -- Best, Daniel --00000000000055478705774228ad 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 AQoCggEBALR23lKtjlZW/17kthzYcMHHKFgywfc4vLIjfq42NmMWbXkNUabIgS8KX4PnIFsTlD6F GO2fqnsTygvYPFBSMX4OCFtJXoikP2CQlEvO7WooyE94tqmqD+w0YtyP2IB5j4KvOIeNv1Gbnnes BIUWLFxs1ERvYDhmk+OrvW7Vd8ZfpRJj71Rb+QQsUpkyTySaqALXnyztTDp1L5d1bABJN/bJbEU3 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