From patchwork Wed Mar 30 15:53:27 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Petr Mladek X-Patchwork-Id: 8699221 Return-Path: X-Original-To: patchwork-linux-sh@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id B8E38C0553 for ; Wed, 30 Mar 2016 15:55:45 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 14A7D2038F for ; Wed, 30 Mar 2016 15:55:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1B24920389 for ; Wed, 30 Mar 2016 15:55:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754641AbcC3Pxz (ORCPT ); Wed, 30 Mar 2016 11:53:55 -0400 Received: from mx2.suse.de ([195.135.220.15]:40563 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753005AbcC3Pxy (ORCPT ); Wed, 30 Mar 2016 11:53:54 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 5B1F2ADE8; Wed, 30 Mar 2016 15:53:51 +0000 (UTC) From: Petr Mladek To: Andrew Morton Cc: Peter Zijlstra , Steven Rostedt , Russell King , Daniel Thompson , Jiri Kosina , Ingo Molnar , Thomas Gleixner , Sergey Senozhatsky , Chris Metcalf , linux-kernel@vger.kernel.org, x86@kernel.org, linux-arm-kernel@lists.infradead.org, adi-buildroot-devel@lists.sourceforge.net, linux-cris-kernel@axis.com, linux-mips@linux-mips.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, Petr Mladek , Jan Kara , Ralf Baechle , Benjamin Herrenschmidt , Martin Schwidefsky , David Miller Subject: [PATCH v4 2/5] printk/nmi: use IRQ work only when ready Date: Wed, 30 Mar 2016 17:53:27 +0200 Message-Id: <1459353210-20260-3-git-send-email-pmladek@suse.com> X-Mailer: git-send-email 1.8.5.6 In-Reply-To: <1459353210-20260-1-git-send-email-pmladek@suse.com> References: <1459353210-20260-1-git-send-email-pmladek@suse.com> Sender: linux-sh-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-sh@vger.kernel.org X-Spam-Status: No, score=-2.9 required=5.0 tests=BAYES_00,RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP 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 479e0764203c..303cf0d15e57 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; } @@ -195,6 +199,13 @@ 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)