From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de ([195.135.220.15]:37936 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934046AbeF0OI2 (ORCPT ); Wed, 27 Jun 2018 10:08:28 -0400 From: Petr Mladek To: Sergey Senozhatsky , Steven Rostedt Cc: Peter Zijlstra , Tetsuo Handa , Sergey Senozhatsky , linux-kernel@vger.kernel.org, stable@vger.kernel.org, Petr Mladek Subject: [PATCH v2 0/3] printk: Deadlock in NMI regression Date: Wed, 27 Jun 2018 16:08:14 +0200 Message-Id: <20180627140817.27764-1-pmladek@suse.com> Sender: stable-owner@vger.kernel.org List-ID: The commit 719f6a7040f1bdaf96 ("printk: Use the main logbuf in NMI when logbuf_lock is available") brought back the possible deadlocks in printk() and NMI. This is rework of the proposed fix, see https://lkml.kernel.org/r/20180606111557.xzs6l3lkvg7lq3ts@pathway.suse.cz I realized that we could rather easily move the check to vprintk_func() and still avoid any race. I believe that this is a win-win solution. Changes against v1: + Move the check from vprintk_emit() to vprintk_func() + More straightforward commit message + Fix build with CONFIG_PRINTK_NMI disabled Petr Mladek (3): printk: Split the code for storing a message into the log buffer printk: Create helper function to queue deferred console handling printk/nmi: Prevent deadlock when accessing the main log buffer in NMI include/linux/printk.h | 4 ++++ kernel/printk/internal.h | 9 ++++++- kernel/printk/printk.c | 57 +++++++++++++++++++++++++++----------------- kernel/printk/printk_safe.c | 58 +++++++++++++++++++++++++++++---------------- kernel/trace/trace.c | 4 +++- lib/nmi_backtrace.c | 3 --- 6 files changed, 87 insertions(+), 48 deletions(-) -- 2.13.7