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=-2.1 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID, USER_AGENT_MUTT autolearn=ham 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 84CB1C43144 for ; Tue, 26 Jun 2018 09:38:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2AB1C25DA4 for ; Tue, 26 Jun 2018 09:38:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="epB0SYbg" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2AB1C25DA4 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934291AbeFZJir (ORCPT ); Tue, 26 Jun 2018 05:38:47 -0400 Received: from merlin.infradead.org ([205.233.59.134]:35046 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932206AbeFZJiq (ORCPT ); Tue, 26 Jun 2018 05:38:46 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.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:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=FIiVtCr1PGtxn9E7KPr2HNRbrWMOr6X5klzP2dE7yYo=; b=epB0SYbgFYwuFJEXmjkFn+bFJ 6BwT+hDtiumnv/F61UBZMPsoOuKVzXnuUZ2L7Ow+MF69FXEbqzNTGYXJW0l3NZ1pFycKBbGkaA6Ls kGysBghdlgPxGGEvYryOfaSgKuPgEsC2neVfg6vXvOT5ECEcqzofwdgn3CY2KEOaNRt8Y9uMORBMj JU9cYtvDSkHTh+CIaBucpn9R2YXF5Ew5PTD4SPHr8rP3CBFcpMclMAs+ebwHDM8cbTFf9QyW/Dkqg nY3EWKaN41pJ9WXCObNAocoAfzCvART9NhUBVcr4JG3S4QGJ+4mx16lIupjLXcevTjl73uCM9mdKF 6pgI7MMSw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1fXkQZ-0007Ha-9Z; Tue, 26 Jun 2018 09:38:23 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id E91062029FA0A; Tue, 26 Jun 2018 11:38:20 +0200 (CEST) Date: Tue, 26 Jun 2018 11:38:20 +0200 From: Peter Zijlstra To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org, Boqun Feng Subject: Re: [PATCH tip/core/rcu 2/2] rcu: Make expedited GPs handle CPU 0 being offline Message-ID: <20180626093820.GG2494@hirez.programming.kicks-ass.net> References: <20180625224308.GA10064@linux.vnet.ibm.com> <20180625224332.10596-2-paulmck@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180625224332.10596-2-paulmck@linux.vnet.ibm.com> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 25, 2018 at 03:43:32PM -0700, Paul E. McKenney wrote: > + preempt_disable(); > + for_each_leaf_node_possible_cpu(rnp, cpu) { > + if (cpu_is_offline(cpu)) /* Preemption disabled. */ > + continue; Create for_each_node_online_cpu() instead? Seems a bit pointless to iterate possible mask only to then check it against the online mask. Just iterate the online mask directly. Or better yet, write this as: preempt_disable(); cpu = cpumask_next(rnp->grplo - 1, cpu_online_mask); if (cpu > rnp->grphi) cpu = WORK_CPU_UNBOUND; queue_work_on(cpu, rcu_par_gp_wq, &rnp->rew.rew_work); preempt_enable(); Which is what it appears to be doing. > + queue_work_on(cpu, rcu_par_gp_wq, &rnp->rew.rew_work); > + rnp->exp_need_flush = true; > + break; > + } > + preempt_enable(); > + if (!rnp->exp_need_flush) { /* All offline, report QSes. */ > + queue_work(rcu_par_gp_wq, &rnp->rew.rew_work); > + rnp->exp_need_flush = true; > + } > } > > /* Wait for workqueue jobs (if any) to complete. */ > -- > 2.17.1 >