From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id C201894F for ; Tue, 26 Jul 2016 14:40:24 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 32B2A1AB for ; Tue, 26 Jul 2016 14:40:24 +0000 (UTC) Message-ID: <1469544015.120686.324.camel@infradead.org> From: David Woodhouse To: Andy Lutomirski Date: Tue, 26 Jul 2016 15:40:15 +0100 In-Reply-To: References: <20160719034717.GA24189@swordfish> <535ebaec-1653-3077-d17b-feb847fd51d2@suse.com> <578EF192.3050808@huawei.com> <028967b8-6107-9d9c-453a-a7f25e967f70@suse.com> <1469097065.120686.124.camel@infradead.org> Content-Type: multipart/signed; micalg="sha-256"; protocol="application/x-pkcs7-signature"; boundary="=-/NMOVjOSNk26Ujb24zLs" Mime-Version: 1.0 Cc: "ksummit-discuss@lists.linuxfoundation.org" Subject: Re: [Ksummit-discuss] [TECH TOPIC] asynchronous printk List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , --=-/NMOVjOSNk26Ujb24zLs Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, 2016-07-21 at 08:05 -0700, Andy Lutomirski wrote: > On Thu, Jul 21, 2016 at 3:31 AM, David Woodhouse wr= ote: > > On Thu, 2016-07-21 at 07:59 +0200, Hannes Reinecke wrote: > > > > If we do all this stuff, can we also try to clean up earlyprintk a > > > > bit? The whole earlyconsole mechanism is a mess, and switching ove= r > > > > to the non-early console is only somewhat functional. I'd love to = see > > > > this all simplified: before there's any console at all available, j= ust > > > > buffer messages. Then, when a console shows up, write the buffer o= ut. > > > > Then earlyprintk can work just like regular printk. > > > >=20 > > > Begging the question how one would debug failures during that time. > > > The current earlyprintk stuff is at least able to print out _somethin= g_, > > > so that you have some idea what went wrong. > > > Without that things will become _really_ hard during board bringup. > >=20 > > No, you don't actually *delay* the console output. You still register > > the console as soon as you physically can, but you just don't have all > > that nasty special-casing of the "earlyprintk" nonsense; you just make > > sure the standard console output is capable of working as early as you > > need it to. >=20 > Agreed. >=20 > If we could convince fbcon to work early (which it really ought to), We had bootx on PowerPC which worked from extremely early. > But doing this really nicely does tie in to the async printk > discussion for a different reason. I think that we should always > initialize the obvious "early" consoles that can be cleanly enumerated > early (e.g. EFI). What we shouldn't do by default is *display* > anything to them unless we crash, because the distro people want a > clean boot to look pretty. ISTM the condition for flushing the async > printk buffers could be the same as the condition for actually writing > to pre-VT consoles. Me no like. That makes even *less* sense for early boot than it does during later runtime. Because even *more* of the 'we crash' scenarios during early boot are going to be uncontrolled "oh shit" happenings, not "oh dear, it looks like we're going to crash so let's helpfully dump out all the console messages before we do so". We already have *really* early command line parsing; we can use that to determine the console loglevel if we need to. No need to be printing debug messages to the console unconditionally and upsetting the graphical boot... --=20 dwmw2 --=-/NMOVjOSNk26Ujb24zLs Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0BBwEAAKCCEeAw ggXiMIIDyqADAgECAhBrp4p9CteI1lEK+Vnk57ThMA0GCSqGSIb3DQEBCwUAMH0xCzAJBgNVBAYT AklMMRYwFAYDVQQKEw1TdGFydENvbSBMdGQuMSswKQYDVQQLEyJTZWN1cmUgRGlnaXRhbCBDZXJ0 aWZpY2F0ZSBTaWduaW5nMSkwJwYDVQQDEyBTdGFydENvbSBDZXJ0aWZpY2F0aW9uIEF1dGhvcml0 eTAeFw0xNTEyMTYwMTAwMDVaFw0zMDEyMTYwMTAwMDVaMHUxCzAJBgNVBAYTAklMMRYwFAYDVQQK Ew1TdGFydENvbSBMdGQuMSkwJwYDVQQLEyBTdGFydENvbSBDZXJ0aWZpY2F0aW9uIEF1dGhvcml0 eTEjMCEGA1UEAxMaU3RhcnRDb20gQ2xhc3MgMSBDbGllbnQgQ0EwggEiMA0GCSqGSIb3DQEBAQUA A4IBDwAwggEKAoIBAQC9fdr3w6J9g/Zbgv3bW1+uHht1wLUZr5gkrLtXedg17AkefMyUGwrQdvwO bhajcVmnKVxhrUwkZPXRAwZZosRHfEIi5FH7x6SV/8Sp5lZEuiMnvMFG2MzLA84J6Ws5T4NfXZ0q 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