From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751491AbbLKNU4 (ORCPT ); Fri, 11 Dec 2015 08:20:56 -0500 Received: from mx2.suse.de ([195.135.220.15]:48193 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750908AbbLKNUy (ORCPT ); Fri, 11 Dec 2015 08:20:54 -0500 From: Petr Mladek To: akpm@linux-foundation.org Cc: linux-kernel@vger.kernel.org, Geert Uytterhoeven , Arnd Bergmann , jkosina@suse.com, pmladek@suse.com Subject: [PATCH v4 2/4] printk/nmi: Use IRQ work only when ready Date: Fri, 11 Dec 2015 14:20:50 +0100 Message-Id: <1449840052-10491-3-git-send-email-pmladek@suse.com> X-Mailer: git-send-email 1.8.5.6 In-Reply-To: <1449840052-10491-1-git-send-email-pmladek@suse.com> References: <1449840052-10491-1-git-send-email-pmladek@suse.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org NMIs could happen at any time. This patch makes sure that the safe printk() in NMI will schedule IRQ work only when the related structs are initialized. All pending messages are flushed when the IRQ work is being initialized. Signed-off-by: Petr Mladek Cc: Jan Kara Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Russell King Cc: Daniel Thompson Cc: Jiri Kosina Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Ralf Baechle Cc: Benjamin Herrenschmidt Cc: Martin Schwidefsky Cc: David Miller Signed-off-by: Andrew Morton --- kernel/printk/nmi.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/kernel/printk/nmi.c b/kernel/printk/nmi.c index b5d1359402c5..9a506bd18b9d 100644 --- a/kernel/printk/nmi.c +++ b/kernel/printk/nmi.c @@ -38,6 +38,7 @@ * were handled or when IRQs are blocked. */ DEFINE_PER_CPU(printk_func_t, printk_func) = vprintk_default; +static int printk_nmi_irq_ready; #define NMI_LOG_BUF_LEN (4096 - sizeof(atomic_t) - sizeof(struct irq_work)) @@ -84,8 +85,11 @@ again: goto again; /* Get flushed in a more safe context. */ - if (add) + if (add && printk_nmi_irq_ready) { + /* Make sure that IRQ work is really initialized. */ + smp_rmb(); irq_work_queue(&s->work); + } return add; } @@ -194,6 +198,13 @@ void __init printk_nmi_init(void) init_irq_work(&s->work, __printk_nmi_flush); } + + /* Make sure that IRQ works are initialized before enabling. */ + smp_wmb(); + printk_nmi_irq_ready = 1; + + /* Flush pending messages that did not have scheduled IRQ works. */ + printk_nmi_flush(); } void printk_nmi_enter(void) -- 1.8.5.6