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=-3.8 required=3.0 tests=BAYES_00,FAKE_REPLY_C, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 791E8C6377A for ; Mon, 19 Jul 2021 05:39:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6124E61184 for ; Mon, 19 Jul 2021 05:39:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233635AbhGSFmy (ORCPT ); Mon, 19 Jul 2021 01:42:54 -0400 Received: from helcar.hmeau.com ([216.24.177.18]:51442 "EHLO deadmen.hmeau.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229777AbhGSFmx (ORCPT ); Mon, 19 Jul 2021 01:42:53 -0400 Received: from gondobar.mordor.me.apana.org.au ([192.168.128.4] helo=gondobar) by deadmen.hmeau.com with esmtp (Exim 4.92 #5 (Debian)) id 1m5Lzk-0004RI-3h; Mon, 19 Jul 2021 13:39:12 +0800 Received: from herbert by gondobar with local (Exim 4.92) (envelope-from ) id 1m5LzP-0004N7-JA; Mon, 19 Jul 2021 13:38:51 +0800 Date: Mon, 19 Jul 2021 13:38:51 +0800 From: Herbert Xu To: Russell King Oracle Cc: hch@lst.de, torvalds@linux-foundation.org, akpm@linux-foundation.org, James.Bottomley@hansenpartnership.com, guoren@kernel.org, tsbogend@alpha.franken.de, nickhu@andestech.com, green.hu@gmail.com, deanbo422@gmail.com, deller@gmx.de, ysato@users.sourceforge.jp, dalias@libc.org, geoff@infradead.org, paul@crapouillou.net, ulf.hansson@linaro.org, alexs@kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-csky@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-sh@vger.kernel.org, linux-mmc@vger.kernel.org, linux-scsi@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org Subject: Re: flush_kernel_dcache_page fixes and removal Message-ID: <20210719053851.GA16780@gondor.apana.org.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210713084648.GF22278@shell.armlinux.org.uk> X-Newsgroups: apana.lists.os.linux.doc,apana.lists.os.linux.kernel,apana.lists.os.linux.scsi Organization: Core User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-sh@vger.kernel.org Russell King Oracle wrote: > > I think you need to be careful - I seem to have a recollection that the > reason we ended up with flush_kernel_dcache_page() was the need to avoid > the taking of the mmap lock for 32-bit ARM VIVT based CPUs in > flush_dcache_page(). 32-bit ARM flush_dcache_page() can block. > > If you're sure that all these changes you're making do not end up > calling flush_dcache_page() from a path where we are atomic, then fine. The Crypto API has been calling flush_dcache_page from softirq context since before the advent of git (see crypto/scatterwalk.c from the initial import). So if 32-bit ARM blocks on it then this has been broken for almost 20 years. Cheers, -- Email: Herbert Xu Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt