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=-6.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS 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 BAFD3C43461 for ; Mon, 14 Sep 2020 19:59:49 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 334CB207EA for ; Mon, 14 Sep 2020 19:59:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 334CB207EA Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=davemloft.net Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 27FB26B0003; Mon, 14 Sep 2020 15:59:48 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 20AB66B0055; Mon, 14 Sep 2020 15:59:48 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1209F6B005D; Mon, 14 Sep 2020 15:59:48 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0032.hostedemail.com [216.40.44.32]) by kanga.kvack.org (Postfix) with ESMTP id EB53D6B0003 for ; Mon, 14 Sep 2020 15:59:47 -0400 (EDT) Received: from smtpin24.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 9F9E5362B for ; Mon, 14 Sep 2020 19:59:47 +0000 (UTC) X-FDA: 77262732414.24.waves71_1c0ae7b2710b Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin24.hostedemail.com (Postfix) with ESMTP id 674E21A4A7 for ; Mon, 14 Sep 2020 19:59:47 +0000 (UTC) X-HE-Tag: waves71_1c0ae7b2710b X-Filterd-Recvd-Size: 2096 Received: from shards.monkeyblade.net (shards.monkeyblade.net [23.128.96.9]) by imf17.hostedemail.com (Postfix) with ESMTP for ; Mon, 14 Sep 2020 19:59:46 +0000 (UTC) Received: from localhost (unknown [IPv6:2601:601:9f00:477::3d5]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) (Authenticated sender: davem-davemloft) by shards.monkeyblade.net (Postfix) with ESMTPSA id 0A5F912354CAC; Mon, 14 Sep 2020 12:42:57 -0700 (PDT) Date: Mon, 14 Sep 2020 12:59:42 -0700 (PDT) Message-Id: <20200914.125942.5644261129883859.davem@davemloft.net> To: npiggin@gmail.com Cc: linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, sparclinux@vger.kernel.org, aneesh.kumar@linux.ibm.com, akpm@linux-foundation.org, axboe@kernel.dk, peterz@infradead.org Subject: Re: [PATCH v2 3/4] sparc64: remove mm_cpumask clearing to fix kthread_use_mm race From: David Miller In-Reply-To: <20200914045219.3736466-4-npiggin@gmail.com> References: <20200914045219.3736466-1-npiggin@gmail.com> <20200914045219.3736466-4-npiggin@gmail.com> X-Mailer: Mew version 6.8 on Emacs 27.1 Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [2620:137:e000::1:9]); Mon, 14 Sep 2020 12:42:58 -0700 (PDT) X-Rspamd-Queue-Id: 674E21A4A7 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Nicholas Piggin Date: Mon, 14 Sep 2020 14:52:18 +1000 ... > The basic fix for sparc64 is to remove its mm_cpumask clearing code. The > optimisation could be effectively restored by sending IPIs to mm_cpumask > members and having them remove themselves from mm_cpumask. This is more > tricky so I leave it as an exercise for someone with a sparc64 SMP. > powerpc has a (currently similarly broken) example. > > Signed-off-by: Nicholas Piggin Sad to see this optimization go away, but what can I do: Acked-by: David S. Miller