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 70037C433E2 for ; Mon, 14 Sep 2020 20:00:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 32672207EA for ; Mon, 14 Sep 2020 20:00:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726013AbgINT7z (ORCPT ); Mon, 14 Sep 2020 15:59:55 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60850 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725964AbgINT7w (ORCPT ); Mon, 14 Sep 2020 15:59:52 -0400 Received: from shards.monkeyblade.net (shards.monkeyblade.net [IPv6:2620:137:e000::1:9]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B9910C06174A; Mon, 14 Sep 2020 12:59:51 -0700 (PDT) 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) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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