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Mon, 20 Jun 2022 08:00:57 +0000 (UTC) X-FDA: 79597868154.01.200205F Received: from eu-smtp-delivery-151.mimecast.com (eu-smtp-delivery-151.mimecast.com [185.58.86.151]) by imf26.hostedemail.com (Postfix) with ESMTP id 45EF51400B6 for ; Mon, 20 Jun 2022 08:00:57 +0000 (UTC) Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id uk-mta-403-45IbctrUOuGrwcXUsijd8g-1; Mon, 20 Jun 2022 09:00:53 +0100 X-MC-Unique: 45IbctrUOuGrwcXUsijd8g-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) by AcuMS.aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) with Microsoft SMTP Server (TLS) id 15.0.1497.36; Mon, 20 Jun 2022 09:00:50 +0100 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.036; Mon, 20 Jun 2022 09:00:50 +0100 From: David Laight To: 'Matthew Wilcox' CC: 'Kent Overstreet' , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "pmladek@suse.com" , "rostedt@goodmis.org" , "enozhatsky@chromium.org" , "linux@rasmusvillemoes.dk" Subject: RE: [PATCH v4 00/34] Printbufs - new data structure for building strings Thread-Topic: [PATCH v4 00/34] Printbufs - new data structure for building strings Thread-Index: AQHYhD6oUJ9HZdIC7US1XHhH4yp3Qa1XsEIg///6OQCAAEQQIA== Date: Mon, 20 Jun 2022 08:00:50 +0000 Message-ID: <576df7d75e3745cbacd3d265349d1a4a@AcuMS.aculab.com> References: <20220620004233.3805-1-kent.overstreet@gmail.com> <0a5901f8460f452a89c9b0cda32fb833@AcuMS.aculab.com> In-Reply-To: Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; 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dkim=none; dmarc=pass (policy=none) header.from=aculab.com; spf=pass (imf26.hostedemail.com: domain of david.laight@aculab.com designates 185.58.86.151 as permitted sender) smtp.mailfrom=david.laight@aculab.com X-Stat-Signature: qimpbp8t3y79qt3bpnwfes4p3utykifp X-Rspamd-Queue-Id: 45EF51400B6 X-HE-Tag: 1655712057-422603 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000227, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Matthew Wilcox > Sent: 20 June 2022 05:55 >=20 > On Mon, Jun 20, 2022 at 04:19:31AM +0000, David Laight wrote: > > I really think that is a bad idea. > > printk() already uses a lot of stack, anything doing a recursive > > call is just making that worse. > > Especially since these calls can often be in error paths > > which are not often tested and can already be on deep stacks. >=20 > You made this complaint last time and I challenged you to provide data. > You have not, as yet, provided data. There is already an issue with printk() needing 2k of stack and 'blowing' the stack in the stack overflow check. This is with KASAN, but that that probably doesn't make a massive difference - especially since it has more stack to play with. =09David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1= PT, UK Registration No: 1397386 (Wales)