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,URIBL_BLOCKED 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 0DE27C43461 for ; Tue, 15 Sep 2020 19:43:00 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 81C0E2078E for ; Tue, 15 Sep 2020 19:42:59 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 81C0E2078E 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 A57A6900050; Tue, 15 Sep 2020 15:42:58 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A077C900028; Tue, 15 Sep 2020 15:42:58 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 91FA8900050; Tue, 15 Sep 2020 15:42:58 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0098.hostedemail.com [216.40.44.98]) by kanga.kvack.org (Postfix) with ESMTP id 7AA44900028 for ; Tue, 15 Sep 2020 15:42:58 -0400 (EDT) Received: from smtpin28.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 35D598249980 for ; Tue, 15 Sep 2020 19:42:58 +0000 (UTC) X-FDA: 77266318836.28.slave59_351606127113 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin28.hostedemail.com (Postfix) with ESMTP id 0DFB86C05 for ; Tue, 15 Sep 2020 19:42:58 +0000 (UTC) X-HE-Tag: slave59_351606127113 X-Filterd-Recvd-Size: 2470 Received: from shards.monkeyblade.net (shards.monkeyblade.net [23.128.96.9]) by imf40.hostedemail.com (Postfix) with ESMTP for ; Tue, 15 Sep 2020 19:42:57 +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 9299113678364; Tue, 15 Sep 2020 12:26:08 -0700 (PDT) Date: Tue, 15 Sep 2020 12:42:54 -0700 (PDT) Message-Id: <20200915.124254.1657521903825160294.davem@davemloft.net> To: npiggin@gmail.com Cc: akpm@linux-foundation.org, aneesh.kumar@linux.ibm.com, axboe@kernel.dk, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, peterz@infradead.org, sparclinux@vger.kernel.org Subject: Re: [PATCH v2 3/4] sparc64: remove mm_cpumask clearing to fix kthread_use_mm race From: David Miller In-Reply-To: <1600139445.qwycwjuwdq.astroid@bobo.none> References: <20200914045219.3736466-4-npiggin@gmail.com> <20200914.125942.5644261129883859.davem@davemloft.net> <1600139445.qwycwjuwdq.astroid@bobo.none> 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]); Tue, 15 Sep 2020 12:26:09 -0700 (PDT) X-Rspamd-Queue-Id: 0DFB86C05 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 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: Tue, 15 Sep 2020 13:24:07 +1000 > Excerpts from David Miller's message of September 15, 2020 5:59 am: >> 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 >> > > Thanks Dave, any objection if we merge this via the powerpc tree > to keep the commits together? No objection.