Received: by 2002:a05:6358:d09b:b0:dc:cd0c:909e with SMTP id jc27csp6554156rwb; Mon, 12 Dec 2022 03:33:55 -0800 (PST) X-Google-Smtp-Source: AA0mqf7189cgbe+ZLPIFSTGBbiwtknNCKzbt/D7PwN4mZCv/B8/7ZbTBToH6Gxhr1QMszd1KwTuV X-Received: by 2002:aa7:8b42:0:b0:566:900e:1d8c with SMTP id i2-20020aa78b42000000b00566900e1d8cmr16550968pfd.8.1670844835120; Mon, 12 Dec 2022 03:33:55 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1670844835; cv=none; d=google.com; s=arc-20160816; b=t26hTdj6cDM/P30Wm+Q5wuxL5DWFeiAqg0lKWKKXuy5KsuvnhDP9X7wbNrDM+DszoX 5hPNVTZ7qTLAqh4h1LV+dhARZYqwP7N2hsJ7cMR+2o2Il3N3Stz8WtDU6z73cPngksNe jZ6K04ZNqd3LD5rmUZ8Vs8nj9JKsXt3aLJzNy18YfvRl2R0sihtA212aSGjmciS4xvmx zlGDnIxrDW5VyEiRkPR+gm/RU2xaiWl0M+3g5/XLo0ood/luOPmFznw2ApZbdnc3PqCA RcJyXXIRBwQ8O8iZoXpuy0vpMTBYetL5fFSgQSX2aSoMI5hJKFRdO2C6OGWChrqIM0uG zjbQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:in-reply-to:content-disposition:mime-version :references:message-id:subject:cc:to:from:date:dkim-signature; bh=aPCq5QjQ7nVUQw50mTEY6sEu3k3UNBF5jPLWNgYPtCo=; b=O1y3qlaIhsJLaF9Fy1ZmBECzMbYzqOl9ackDzCE3Fx7oSZG1qXB1x/ePlb0HkGb9gl rzZZmVmvusQqY/fqGVAhw2Qr129zw0g5PaGmiN8ePladPh+wc3MFhUL493lf0cOsMChv cmyE6ab6bpAv/Lj6+Kmom7G1+/Wa4C2TdQkSZf84fdctlmklf5todhqp8nNC4NAnteqR gPp+wJFQ6gss2R3NWvjC2HIhjrCONJBAuiCP+1rUlsRJFPiZSY3P13zZI8wmokLMf6Os xxGxBmM7GiOTihIbKvjNxv8RW1I40jnOvGNaZiOTyrHcWggjTE6IZCVM0dYiSqB7ed7i /CMA== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@infradead.org header.s=desiato.20200630 header.b=VCOxZarE; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Return-Path: Received: from out1.vger.email (out1.vger.email. [2620:137:e000::1:20]) by mx.google.com with ESMTP id t14-20020a056a00138e00b00575d6a4ba9bsi9958834pfg.307.2022.12.12.03.33.44; Mon, 12 Dec 2022 03:33:55 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=desiato.20200630 header.b=VCOxZarE; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231408AbiLLL2x (ORCPT + 76 others); Mon, 12 Dec 2022 06:28:53 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41460 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231302AbiLLL2v (ORCPT ); Mon, 12 Dec 2022 06:28:51 -0500 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 07F6231E; Mon, 12 Dec 2022 03:28:51 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; 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=aPCq5QjQ7nVUQw50mTEY6sEu3k3UNBF5jPLWNgYPtCo=; b=VCOxZarE3hZ5ss5LXGp/ijHe1b /ntM61IKrd0dlYLrD3IGZ8OXhAtkYj9dZMNWZhAArywAgtrbb2KpCN3Wqp3zhzS8+vbsKEb+D2RpC O/vg1NBlFWQfmUl5jy8/NrHgbbhlk8spZ+B5heH5Q6kXhkxgzgLJk9YeggwhcL3FwZcbbU1vH5O0v IifRdNjkPZ2YlcFdtmchRz6Igd6pRCJd35BWocTIvogTMTpXf89l58aAdC4ddEzc1+Z1czngaoKvA Oq6mL24LGP1rrvwrssX4LE+yGVY2Bzmdg3dbhFPzKCduh0AN/aWTRnFyY0l/WHDDv0wNLA4AaLEbv PAn6ZPIQ==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1p4gz0-009lF1-F9; Mon, 12 Dec 2022 11:28:30 +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 (4096 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id E6354300293; Mon, 12 Dec 2022 12:28:29 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id C910E20B2B4EA; Mon, 12 Dec 2022 12:28:29 +0100 (CET) Date: Mon, 12 Dec 2022 12:28:29 +0100 From: Peter Zijlstra To: Tejun Heo Cc: torvalds@linux-foundation.org, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@kernel.org, joshdon@google.com, brho@google.com, pjt@google.com, derkling@google.com, haoluo@google.com, dvernet@meta.com, dschatzberg@meta.com, dskarlat@cs.cmu.edu, riel@surriel.com, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, kernel-team@meta.com Subject: Re: [PATCH 06/31] sched: Add sched_class->switching_to() and expose check_class_changing/changed() Message-ID: References: <20221130082313.3241517-1-tj@kernel.org> <20221130082313.3241517-7-tj@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221130082313.3241517-7-tj@kernel.org> X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED,SPF_HELO_NONE, SPF_NONE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 29, 2022 at 10:22:48PM -1000, Tejun Heo wrote: > When a task switches to a new sched_class, the prev and new classes are > notified through ->switched_from() and ->switched_to(), respectively, after > the switching is done. However, a new sched_class needs to prepare the task > state before it is enqueued on the new class for the first time. How and why isn't sched_fork() sufficient?