Received: by 2002:a05:6358:1087:b0:cb:c9d3:cd90 with SMTP id j7csp4075182rwi; Mon, 17 Oct 2022 00:43:13 -0700 (PDT) X-Google-Smtp-Source: AMsMyM4JJG5hjn5EDQWr3uNJ3OIgCJ+GEEWEc9cbsmd5LvyBZdUk4+/ZJ06N9SNhBKTy3yhW1RIw X-Received: by 2002:a17:90b:1e4c:b0:20d:8cf0:1a46 with SMTP id pi12-20020a17090b1e4c00b0020d8cf01a46mr12397324pjb.164.1665992592937; Mon, 17 Oct 2022 00:43:12 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1665992592; cv=none; d=google.com; s=arc-20160816; b=LrAR8Yf19dSLi8mB6n7R2Xv/So6Y7OlAs1Gp8Z9QLFeaXkbjqFNKRu/MfOMhsxP7cD wGgrfgrww6l/5KefOlGRE+5uR4CufE9Cb3+6EP/SM3n/byHRLOyMFiGLbYOIuQByt3SQ 2h0FswF+TZAmbSkhCPhpJllNQL6SvxO/AdQcyEkcN3kND53K9nCLZlmAD1Mti0So+Ho4 msI0hNRv99h9fAvcoi0KzSyT8wlTXYeJPKgmF7EX/ctgKGWqDKy0DkqOEwfdw9woZlDt Y+ei6GKQF2AFcOgAIFT5ITlK8FtJXpvPtOg8wnGSeXJ+k2fdWo4Ecm5AOv0SqF8eVTeQ /JRQ== 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=MQuxp9USYpLXeUl20/SiKvpty8XB9IEambUSzY8WQ8o=; b=0b8VPm/JED7LK6Ek0VTvqEWYB82k726OJk8LkpKFfWWOqP+MlBQY6dvvAidXjU1WPv /ZZDT8TJR4Ya9EMeT7R/qAPfOunapIJh6iKK6Fc8kQkTSQxFHMXTjF+3BNgaeD1hKfgo 4mW+uOTPAfTqNJKICaxGmMAJ+I8+/TgP4cuqNmlRouaF8w9ltJMbcNT6s2TXzxCIKHwl JdLLn/cr1TIJ4AycpoB7VsxstpYYE4wMnf6jLJU7o8oIwCOx3gF6sqJJZaPMQt0lUm9w SwYe3gJKrvRxUt933Vr4kesvtKvaxLknOZx7ELmE5YgPH8lTScF2lkr9JOlz1QW0+EJ0 vEPg== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@infradead.org header.s=casper.20170209 header.b=Lj0r3XlM; 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 y193-20020a638aca000000b0044c67258354si11314273pgd.800.2022.10.17.00.43.00; Mon, 17 Oct 2022 00:43:12 -0700 (PDT) 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=casper.20170209 header.b=Lj0r3XlM; 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 S229900AbiJQH05 (ORCPT + 99 others); Mon, 17 Oct 2022 03:26:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58090 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229818AbiJQH0y (ORCPT ); Mon, 17 Oct 2022 03:26:54 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 00D715A3D8 for ; Mon, 17 Oct 2022 00:26:51 -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=MQuxp9USYpLXeUl20/SiKvpty8XB9IEambUSzY8WQ8o=; b=Lj0r3XlMKD32EH5VQ+f3X/tmoH 8qKkGL33XRN0ktLamG5QlPl0ENcAEzBN05gx8Vy66gfLKBspm+Ck0ec8XrpmQ5kkVCKzb1ePk9pni G9zskSj6Ue1/exbwjajeTVSFSpgZn41F9/gZNpJvO0fl+PlsKiC/t6ONOw3Q80yk99htlb3ZkKSv6 EZ6gACxIyvWtXQy4UGC0bMp+Hk+WmItCFcD7ffgU0HP7oHw5lTrwoI+eDS1GclORHObYPVuFSxNrl SN0qjALwnd2DN50bu5jNxsD1cT8CXY2PvVwKytVoo+iHDAew++pt7rsbFF2TLb9TPf4Zdixi8/l3k tsOM63mQ==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1okKW9-009g1w-Ll; Mon, 17 Oct 2022 07:26:34 +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) server-digest SHA256) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 764DE300574; Mon, 17 Oct 2022 09:26:27 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 4F03420426DE2; Mon, 17 Oct 2022 09:26:27 +0200 (CEST) Date: Mon, 17 Oct 2022 09:26:27 +0200 From: Peter Zijlstra To: Steven Rostedt Cc: Joel Fernandes , Connor O'Brien , linux-kernel@vger.kernel.org, kernel-team@android.com, John Stultz , Qais Yousef , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Valentin Schneider , Will Deacon , Waiman Long , Boqun Feng , "Paul E . McKenney" , youssefesmat@google.com Subject: Re: [RFC PATCH 07/11] sched: Add proxy execution Message-ID: References: <20221003214501.2050087-1-connoro@google.com> <20221003214501.2050087-8-connoro@google.com> <20221016164809.6cd6871f@rorschach.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221016164809.6cd6871f@rorschach.local.home> 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 Sun, Oct 16, 2022 at 04:48:09PM -0400, Steven Rostedt wrote: > On Sat, 15 Oct 2022 15:53:19 +0200 > Peter Zijlstra wrote: > > > >From this it is easy to see that the critical secion executes with the > > direct sum of the blockchain as a whole (all of them will have donated > > their relative time to make the owner elegible again) -- provided the > > critical section is of course long enough for this to matter (or it's > > owner's weight small enough etc..). > > Does this mean that a lower priority task could do a sort of DOS attack > on a high priority task, if it creates a bunch of threads that > constantly grabs a shared lock from the higher priority task? That is, > the higher priority task could possibly lose a lot of its quota due to > other tasks running on its behalf in the critical section? Less than without PE; without PE the high prio task will be blocked and starved, with PE at least they'll help push the low prio thing ahead and get on with things. Additionally, the highest priotiy waiter will get the lock next.