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=-3.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, 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 2F6E3C56201 for ; Thu, 19 Nov 2020 18:08:56 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id A65592225B for ; Thu, 19 Nov 2020 18:08:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="oFY2qZtN" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A65592225B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:MIME-Version:Date:In-reply-to:Message-ID:Subject:To: From:References:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=yo3qP0uZnam6dBVbuYHx0vZJYtyLlIeD9F3QOVHw7I8=; b=oFY2qZtNj0OMKUcVCcR9Qjaw5 wWpsmV3ZFB4vOUd9x+Ud+soYCPbTQBx4XyZFQbfxlQwwsJ4NOIV9xb3RkUSLsywdF6KZ3JceEi8md /LbLTpAgK5jEDQsBZxsd3nJRFHu2prSllJI4BP8w+g/YXzZQL5O8u3cNF2nAU6VYzEeaFCuNwccAR aG5uQ140J9LIQptBChqlP4RiBYxDLb4gRZk7QdZSy1Qycr1ec8lPCOBY+wMnhkXAHj0tiqCCRrbOn H/sbGgG4VOL93c7Wlv3xTdBwF7rEK85l1sVWTd/CP5A91bD5JmSVEF4OYNCk+M4f7h79uewlfmZRg h0NB2BQcw==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kfoLe-0003yB-BQ; Thu, 19 Nov 2020 18:07:58 +0000 Received: from foss.arm.com ([217.140.110.172]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kfnFT-0005iZ-Bk for linux-arm-kernel@lists.infradead.org; Thu, 19 Nov 2020 16:57:33 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id D5C441396; Thu, 19 Nov 2020 08:57:29 -0800 (PST) Received: from e113632-lin (e113632-lin.cambridge.arm.com [10.1.194.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 868F53F718; Thu, 19 Nov 2020 08:57:27 -0800 (PST) References: <20201113093720.21106-1-will@kernel.org> <20201113093720.21106-8-will@kernel.org> <20201119131319.GE4331@willie-the-truck> <20201119160944.GP3121392@hirez.programming.kicks-ass.net> User-agent: mu4e 0.9.17; emacs 26.3 From: Valentin Schneider To: Peter Zijlstra Subject: Re: [PATCH v3 07/14] sched: Introduce restrict_cpus_allowed_ptr() to limit task CPU affinity Message-ID: In-reply-to: <20201119160944.GP3121392@hirez.programming.kicks-ass.net> Date: Thu, 19 Nov 2020 16:57:22 +0000 MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201119_115731_545461_CFF6D9E1 X-CRM114-Status: GOOD ( 10.74 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, Juri Lelli , kernel-team@android.com, Vincent Guittot , Ingo Molnar , Greg Kroah-Hartman , Catalin Marinas , Quentin Perret , linux-kernel@vger.kernel.org, Qais Yousef , Suren Baghdasaryan , Johannes Weiner , Li Zefan , Marc Zyngier , Tejun Heo , Will Deacon , Morten Rasmussen , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 19/11/20 16:09, Peter Zijlstra wrote: > On Thu, Nov 19, 2020 at 01:13:20PM +0000, Will Deacon wrote: > >> Sure, but I was talking about what userspace sees, and I don't think it ever >> sees CPUs that have been hotplugged off, right? That is, sched_getaffinity() >> masks its result with the active_mask. > > # for i in /sys/devices/system/cpu/cpu*/online; do echo -n $i ":"; cat $i; done > /sys/devices/system/cpu/cpu1/online :0 > /sys/devices/system/cpu/cpu2/online :1 > /sys/devices/system/cpu/cpu3/online :1 > /sys/devices/system/cpu/cpu4/online :1 > /sys/devices/system/cpu/cpu5/online :1 > /sys/devices/system/cpu/cpu6/online :1 > /sys/devices/system/cpu/cpu7/online :1 > > # grep Cpus_allowed /proc/self/status > Cpus_allowed: ff > Cpus_allowed_list: 0-7 > > > :-) Harumph, so there is that... $ while true; do continue; done & $ PID=$! $ taskset -pc 0-1 $PID pid 849's current affinity list: 0-5 pid 849's new affinity list: 0,1 $ echo 0 > /sys/devices/system/cpu/cpu1/online [12578.545726] CPU1: shutdown [12578.548454] psci: CPU1 killed (polled 0 ms) $ taskset -pc $PID pid 849's current affinity list: 0 $ cat /proc/$PID/status | grep Cpus Cpus_allowed: 03 Cpus_allowed_list: 0-1 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel