From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753794AbbC0JZj (ORCPT ); Fri, 27 Mar 2015 05:25:39 -0400 Received: from mail.skyhub.de ([78.46.96.112]:58680 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753508AbbC0JYx (ORCPT ); Fri, 27 Mar 2015 05:24:53 -0400 From: Borislav Petkov To: linux-edac Cc: Jiri Kosina , Borislav Petkov , "Rafael J. Wysocki" , Len Brown , Tony Luck , Tomasz Nowicki , "Chen, Gong" , Wolfram Sang , Lv Zheng , Naoya Horiguchi , linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [RFC PATCH 5/5] GHES: Make NMI handler have a single reader Date: Fri, 27 Mar 2015 10:22:58 +0100 Message-Id: <1427448178-20689-6-git-send-email-bp@alien8.de> X-Mailer: git-send-email 2.3.3 In-Reply-To: <1427448178-20689-1-git-send-email-bp@alien8.de> References: <1427448178-20689-1-git-send-email-bp@alien8.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Jiri Kosina Since GHES sources are global, we theoretically need only a single CPU reading them per NMI instead of a thundering herd of CPUs waiting on a spinlock in NMI context for no reason at all. Do that. Signed-off-by: Jiri Kosina Signed-off-by: Borislav Petkov --- drivers/acpi/apei/ghes.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c index 94a44bad5576..2bfd53cbfe80 100644 --- a/drivers/acpi/apei/ghes.c +++ b/drivers/acpi/apei/ghes.c @@ -729,10 +729,10 @@ static struct llist_head ghes_estatus_llist; static struct irq_work ghes_proc_irq_work; /* - * NMI may be triggered on any CPU, so ghes_nmi_lock is used for - * mutual exclusion. + * NMI may be triggered on any CPU, so ghes_in_nmi is used for + * having only one concurrent reader. */ -static DEFINE_RAW_SPINLOCK(ghes_nmi_lock); +static atomic_t ghes_in_nmi = ATOMIC_INIT(0); static LIST_HEAD(ghes_nmi); @@ -840,7 +840,9 @@ static int ghes_notify_nmi(unsigned int cmd, struct pt_regs *regs) struct ghes *ghes; int sev, ret = NMI_DONE; - raw_spin_lock(&ghes_nmi_lock); + if (!atomic_add_unless(&ghes_in_nmi, 1, 1)) + return ret; + list_for_each_entry_rcu(ghes, &ghes_nmi, list) { if (ghes_read_estatus(ghes, 1)) { ghes_clear_estatus(ghes); @@ -863,7 +865,7 @@ static int ghes_notify_nmi(unsigned int cmd, struct pt_regs *regs) #ifdef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG irq_work_queue(&ghes_proc_irq_work); #endif - raw_spin_unlock(&ghes_nmi_lock); + atomic_dec(&ghes_in_nmi); return ret; } -- 2.3.3