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=-9.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 5B2FDC49ED7 for ; Thu, 19 Sep 2019 17:38:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 25D1421D79 for ; Thu, 19 Sep 2019 17:38:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=efficios.com header.i=@efficios.com header.b="ts/CR1lk" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404287AbfISRij (ORCPT ); Thu, 19 Sep 2019 13:38:39 -0400 Received: from mail.efficios.com ([167.114.142.138]:33778 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404007AbfISRif (ORCPT ); Thu, 19 Sep 2019 13:38:35 -0400 Received: from localhost (ip6-localhost [IPv6:::1]) by mail.efficios.com (Postfix) with ESMTP id 30CD63318CA; Thu, 19 Sep 2019 13:38:34 -0400 (EDT) Received: from mail.efficios.com ([IPv6:::1]) by localhost (mail02.efficios.com [IPv6:::1]) (amavisd-new, port 10032) with ESMTP id c9qwR2L27jPs; Thu, 19 Sep 2019 13:38:33 -0400 (EDT) Received: from localhost (ip6-localhost [IPv6:::1]) by mail.efficios.com (Postfix) with ESMTP id CB3FC3318C3; Thu, 19 Sep 2019 13:38:33 -0400 (EDT) DKIM-Filter: OpenDKIM Filter v2.10.3 mail.efficios.com CB3FC3318C3 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=efficios.com; s=default; t=1568914713; bh=Y+foybCeNbY5nGOuie70SNczfUyOhWGU3VGcIe+vLvk=; h=From:To:Date:Message-Id; b=ts/CR1lkpviQ4sXmC8h0iLzZsvtJEsIGHWZllOqGUTjgs1CTA4aLhmEwWc1POC+tw Kbd+JWVB9DDO8QbY2Li+S5Ang0g3oGdvL+zMaxi6I49j2BtcxsmcyL5CRRfZthyFLn wh9qIgPJ27A5KquBPuvyHjWJHE6v5JewCY5YKWz9AGUaB2pYvLXn0hkc0DYZI/QgHH Hcaa5zpbhaTFJlqPjBMuW8CTAGEtQZJiNJ2DO33hnPI53BG76MBzQ2Cwxmg72Xzgna BC9tEkNVDGT15kj7qLnTRovTmwH2swTPcYfZAfAXc3KA+mJrJiHvhQUztFFiJlxUnU Pme5diEaARyPA== X-Virus-Scanned: amavisd-new at efficios.com Received: from mail.efficios.com ([IPv6:::1]) by localhost (mail02.efficios.com [IPv6:::1]) (amavisd-new, port 10026) with ESMTP id YUIHJmI0aXzJ; Thu, 19 Sep 2019 13:38:33 -0400 (EDT) Received: from localhost.localdomain (192-222-181-218.qc.cable.ebox.net [192.222.181.218]) by mail.efficios.com (Postfix) with ESMTPSA id BEFD933188E; Thu, 19 Sep 2019 13:38:31 -0400 (EDT) From: Mathieu Desnoyers To: Peter Zijlstra , "Paul E. McKenney" Cc: Ingo Molnar , linux-kernel@vger.kernel.org, Oleg Nesterov , "Eric W. Biederman" , Linus Torvalds , Russell King - ARM Linux admin , Chris Metcalf , Christoph Lameter , Kirill Tkhai , Mike Galbraith , Thomas Gleixner , Mathieu Desnoyers Subject: [RFC PATCH for 5.4 6/7] sched/membarrier: Skip IPIs when mm->mm_users == 1 Date: Thu, 19 Sep 2019 13:37:04 -0400 Message-Id: <20190919173705.2181-7-mathieu.desnoyers@efficios.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190919173705.2181-1-mathieu.desnoyers@efficios.com> References: <20190919173705.2181-1-mathieu.desnoyers@efficios.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If there is only a single mm_user for the mm, the private expedited membarrier command can skip the IPIs, because only a single thread is using the mm. Signed-off-by: Mathieu Desnoyers Cc: "Paul E. McKenney" Cc: Peter Zijlstra Cc: Oleg Nesterov Cc: "Eric W. Biederman" Cc: Linus Torvalds Cc: Russell King - ARM Linux admin Cc: Chris Metcalf Cc: Christoph Lameter Cc: Kirill Tkhai Cc: Mike Galbraith Cc: Thomas Gleixner Cc: Ingo Molnar --- kernel/sched/membarrier.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/kernel/sched/membarrier.c b/kernel/sched/membarrier.c index fce06a2e1d89..8afbdf92be0a 100644 --- a/kernel/sched/membarrier.c +++ b/kernel/sched/membarrier.c @@ -145,20 +145,21 @@ static int membarrier_private_expedited(int flags) int cpu; bool fallback = false; cpumask_var_t tmpmask; + struct mm_struct *mm = current->mm; if (flags & MEMBARRIER_FLAG_SYNC_CORE) { if (!IS_ENABLED(CONFIG_ARCH_HAS_MEMBARRIER_SYNC_CORE)) return -EINVAL; - if (!(atomic_read(¤t->mm->membarrier_state) & + if (!(atomic_read(&mm->membarrier_state) & MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE_READY)) return -EPERM; } else { - if (!(atomic_read(¤t->mm->membarrier_state) & + if (!(atomic_read(&mm->membarrier_state) & MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY)) return -EPERM; } - if (num_online_cpus() == 1) + if (atomic_read(&mm->mm_users) == 1 || num_online_cpus() == 1) return 0; /* @@ -193,7 +194,7 @@ static int membarrier_private_expedited(int flags) if (cpu == raw_smp_processor_id()) continue; p = task_rcu_dereference(&cpu_rq(cpu)->curr); - if (p && p->mm == current->mm) { + if (p && p->mm == mm) { if (!fallback) __cpumask_set_cpu(cpu, tmpmask); else -- 2.17.1