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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 DD40EC4338F for ; Wed, 18 Aug 2021 11:56:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C002C60462 for ; Wed, 18 Aug 2021 11:56:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234872AbhHRL4f (ORCPT ); Wed, 18 Aug 2021 07:56:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42466 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232574AbhHRL4U (ORCPT ); Wed, 18 Aug 2021 07:56:20 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 50F40C061764; Wed, 18 Aug 2021 04:55:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=D6iemufMr2b/qeAUmVa3U7ugTs+hnH9TTpLcRzXpGLw=; b=HNIGBYXuOLuf/lXvjO9O83UPQ7 om2IyVQGCUigapiedkWriTOLxcCJ4qmBMuKWxY25raV2fYL2Bs6Crurp/aO02dc2oCrNvZ0ChNqGF a5n4TFrYp+8x+DWYzLn9UZNJosybpHXFOLIx9jCr4lpLZv3/Wc9+sAM+VO8/xEs7EIG7uBkJpxwBz BJs36qSbWjGrvl5gRZQ4zNeN4dDOAD2aB34KRCKmyYe7nXiGoZIkzi33NUNdZXXxQM3g/yuRyNCRq byD34aUA30Ac8t071fMzM7uD/y0YLKxlMdIi8FZPPusHizzK0pxg5EtjdKVYtqB5w/UXKZj9kmcJ5 LPlLDiWw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1mGK8P-003mac-LY; Wed, 18 Aug 2021 11:53:44 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 900E6300233; Wed, 18 Aug 2021 13:53:28 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 7303F2027DC71; Wed, 18 Aug 2021 13:53:28 +0200 (CEST) Date: Wed, 18 Aug 2021 13:53:28 +0200 From: Peter Zijlstra To: Will Deacon Cc: linux-arm-kernel@lists.infradead.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, Catalin Marinas , Marc Zyngier , Greg Kroah-Hartman , Morten Rasmussen , Qais Yousef , Suren Baghdasaryan , Quentin Perret , Tejun Heo , Johannes Weiner , Ingo Molnar , Juri Lelli , Vincent Guittot , "Rafael J. Wysocki" , Dietmar Eggemann , Daniel Bristot de Oliveira , Valentin Schneider , Mark Rutland , kernel-team@android.com Subject: Re: [PATCH v11 08/16] sched: Allow task CPU affinity to be restricted on asymmetric systems Message-ID: References: <20210730112443.23245-1-will@kernel.org> <20210730112443.23245-9-will@kernel.org> <20210818104227.GA13828@willie-the-truck> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 18, 2021 at 12:56:41PM +0200, Peter Zijlstra wrote: > On Wed, Aug 18, 2021 at 11:42:28AM +0100, Will Deacon wrote: > > I think the idea looks good, but perhaps we could wrap things up a bit: > > > > /* Comment about why this is useful with RT */ > > static cpumask_t *clear_user_cpus_ptr(struct task_struct *p) > > { > > struct cpumask *user_mask = NULL; > > > > swap(user_mask, p->user_cpus_ptr); > > return user_mask; > > } > > > > void release_user_cpus_ptr(struct task_struct *p) > > { > > kfree(clear_user_cpus_ptr(p)); > > } > > > > Then just use clear_user_cpus_ptr() in sched/core.c where we know what > > we're doing (well, at least one of us does!). > > OK, I'll go make it like that. Something like so then? --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2497,10 +2497,18 @@ int dup_user_cpus_ptr(struct task_struct return 0; } +static inline struct cpumask *clear_user_cpus_ptr(struct task_struct *p) +{ + struct cpumask *user_mask = NULL; + + swap(p->user_cpus_ptr, user_mask); + + return user_mask; +} + void release_user_cpus_ptr(struct task_struct *p) { - kfree(p->user_cpus_ptr); - p->user_cpus_ptr = NULL; + kfree(clear_user_cpus_ptr(p)); } /* @@ -2733,6 +2741,7 @@ static int __set_cpus_allowed_ptr_locked const struct cpumask *cpu_allowed_mask = task_cpu_possible_mask(p); const struct cpumask *cpu_valid_mask = cpu_active_mask; bool kthread = p->flags & PF_KTHREAD; + struct cpumask *user_mask = NULL; unsigned int dest_cpu; int ret = 0; @@ -2792,9 +2801,13 @@ static int __set_cpus_allowed_ptr_locked __do_set_cpus_allowed(p, new_mask, flags); if (flags & SCA_USER) - release_user_cpus_ptr(p); + user_mask = clear_user_cpus_ptr(p); - return affine_move_task(rq, p, rf, dest_cpu, flags); + ret = affine_move_task(rq, p, rf, dest_cpu, flags); + + kfree(user_mask); + + return ret; out: task_rq_unlock(rq, p, rf); @@ -2941,20 +2954,22 @@ __sched_setaffinity(struct task_struct * */ void relax_compatible_cpus_allowed_ptr(struct task_struct *p) { + struct cpumask *user_mask = p->user_cpus_ptr; unsigned long flags; - struct cpumask *mask = p->user_cpus_ptr; /* * Try to restore the old affinity mask. If this fails, then * we free the mask explicitly to avoid it being inherited across * a subsequent fork(). */ - if (!mask || !__sched_setaffinity(p, mask)) + if (!user_mask || !__sched_setaffinity(p, user_mask)) return; raw_spin_lock_irqsave(&p->pi_lock, flags); - release_user_cpus_ptr(p); + user_mask = clear_user_cpus_ptr(p); raw_spin_unlock_irqrestore(&p->pi_lock, flags); + + kfree(user_mask); } void set_task_cpu(struct task_struct *p, unsigned int new_cpu)