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 3C959C3A5A6 for ; Thu, 19 Sep 2019 17:38:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F207E2196E for ; Thu, 19 Sep 2019 17:38:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=efficios.com header.i=@efficios.com header.b="Wxm7fGN+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404410AbfISRiw (ORCPT ); Thu, 19 Sep 2019 13:38:52 -0400 Received: from mail.efficios.com ([167.114.142.138]:33808 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404041AbfISRif (ORCPT ); Thu, 19 Sep 2019 13:38:35 -0400 Received: from localhost (ip6-localhost [IPv6:::1]) by mail.efficios.com (Postfix) with ESMTP id A99453318DC; 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 vxAVBfIg62Gm; Thu, 19 Sep 2019 13:38:34 -0400 (EDT) Received: from localhost (ip6-localhost [IPv6:::1]) by mail.efficios.com (Postfix) with ESMTP id 427EA3318D5; Thu, 19 Sep 2019 13:38:34 -0400 (EDT) DKIM-Filter: OpenDKIM Filter v2.10.3 mail.efficios.com 427EA3318D5 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=efficios.com; s=default; t=1568914714; bh=72Das0OPV9KlLsKcm7XxjdznJXHbh2C41hlTCYLQ4U4=; h=From:To:Date:Message-Id; b=Wxm7fGN+28QkUTtldNV/lmnXeYsbE8HTm8B6Piv1RUSB8UggV1DY6Yct1bWdLz+4e Aa+R73vxJnIF7arhF9FDq3BrU9ED9RZbKnyIavLEQbv/fokndUHP6D4KSPZG7MocnZ 6h/Fiu5zgS6WBymuroM9SYjEmL/iAwP4His9VE81Y5C3AXaZOgGuCC1Fx3LvvJRqP9 PhajqSp7uq69BGBDdHoSU30w5w1DIV9YU2/8bD2hZBjzjDNsp5Me0NcfDSN0/AO9Rg 54GvSBgc3qtwcRHnRbVG7JhjUzL1105sKpvrA/G14m93H6lFJyN+gdtqAIVNC0Gznj USgchkPWWaZww== 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 AgMXqXRzIKNY; Thu, 19 Sep 2019 13:38:34 -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 0FDD2331896; Thu, 19 Sep 2019 13:38:32 -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 7/7] sched/membarrier: Return -ENOMEM to userspace on memory allocation failure Date: Thu, 19 Sep 2019 13:37:05 -0400 Message-Id: <20190919173705.2181-8-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 Remove the IPI fallback code from membarrier to deal with very infrequent cpumask memory allocation failure. Use GFP_KERNEL rather than GFP_NOWAIT, and relax the blocking guarantees for the expedited membarrier system call commands, allowing it to block if waiting for memory to be made available. In addition, now -ENOMEM can be returned to user-space if the cpumask memory allocation fails. 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 | 61 ++++++++++++--------------------------- 1 file changed, 19 insertions(+), 42 deletions(-) diff --git a/kernel/sched/membarrier.c b/kernel/sched/membarrier.c index 8afbdf92be0a..1420c656e8f0 100644 --- a/kernel/sched/membarrier.c +++ b/kernel/sched/membarrier.c @@ -66,7 +66,6 @@ void membarrier_exec_mmap(struct mm_struct *mm) static int membarrier_global_expedited(void) { int cpu; - bool fallback = false; cpumask_var_t tmpmask; if (num_online_cpus() == 1) @@ -78,15 +77,8 @@ static int membarrier_global_expedited(void) */ smp_mb(); /* system call entry is not a mb. */ - /* - * Expedited membarrier commands guarantee that they won't - * block, hence the GFP_NOWAIT allocation flag and fallback - * implementation. - */ - if (!zalloc_cpumask_var(&tmpmask, GFP_NOWAIT)) { - /* Fallback for OOM. */ - fallback = true; - } + if (!zalloc_cpumask_var(&tmpmask, GFP_KERNEL)) + return -ENOMEM; cpus_read_lock(); rcu_read_lock(); @@ -117,18 +109,15 @@ static int membarrier_global_expedited(void) if (p->flags & PF_KTHREAD) continue; - if (!fallback) - __cpumask_set_cpu(cpu, tmpmask); - else - smp_call_function_single(cpu, ipi_mb, NULL, 1); + __cpumask_set_cpu(cpu, tmpmask); } rcu_read_unlock(); - if (!fallback) { - preempt_disable(); - smp_call_function_many(tmpmask, ipi_mb, NULL, 1); - preempt_enable(); - free_cpumask_var(tmpmask); - } + + preempt_disable(); + smp_call_function_many(tmpmask, ipi_mb, NULL, 1); + preempt_enable(); + + free_cpumask_var(tmpmask); cpus_read_unlock(); /* @@ -143,7 +132,6 @@ static int membarrier_global_expedited(void) static int membarrier_private_expedited(int flags) { int cpu; - bool fallback = false; cpumask_var_t tmpmask; struct mm_struct *mm = current->mm; @@ -168,15 +156,8 @@ static int membarrier_private_expedited(int flags) */ smp_mb(); /* system call entry is not a mb. */ - /* - * Expedited membarrier commands guarantee that they won't - * block, hence the GFP_NOWAIT allocation flag and fallback - * implementation. - */ - if (!zalloc_cpumask_var(&tmpmask, GFP_NOWAIT)) { - /* Fallback for OOM. */ - fallback = true; - } + if (!zalloc_cpumask_var(&tmpmask, GFP_KERNEL)) + return -ENOMEM; cpus_read_lock(); rcu_read_lock(); @@ -194,20 +175,16 @@ 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 == mm) { - if (!fallback) - __cpumask_set_cpu(cpu, tmpmask); - else - smp_call_function_single(cpu, ipi_mb, NULL, 1); - } + if (p && p->mm == mm) + __cpumask_set_cpu(cpu, tmpmask); } rcu_read_unlock(); - if (!fallback) { - preempt_disable(); - smp_call_function_many(tmpmask, ipi_mb, NULL, 1); - preempt_enable(); - free_cpumask_var(tmpmask); - } + + preempt_disable(); + smp_call_function_many(tmpmask, ipi_mb, NULL, 1); + preempt_enable(); + + free_cpumask_var(tmpmask); cpus_read_unlock(); /* -- 2.17.1