From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932789AbaD1Qfx (ORCPT ); Mon, 28 Apr 2014 12:35:53 -0400 Received: from mga11.intel.com ([192.55.52.93]:31256 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755903AbaD1Qfm (ORCPT ); Mon, 28 Apr 2014 12:35:42 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.97,945,1389772800"; d="scan'208";a="529928156" From: "Shevchenko, Andriy" To: Jan Kara , Andrew Morton CC: "linux-kernel@vger.kernel.org" , "Steven Rostedt" Subject: lockdep warning after recent cleanup in console code Thread-Topic: lockdep warning after recent cleanup in console code Thread-Index: AQHPYv/bwdBQHvpujU+9YJZBYRAh9g== Date: Mon, 28 Apr 2014 16:35:26 +0000 Message-ID: <1398702925.11914.292.camel@smile.fi.intel.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.237.72.73] Content-Type: text/plain; charset="utf-8" Content-ID: <66DBDD546D622449882483A1A6E51D56@intel.com> MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by mail.home.local id s3SGaTeZ025240 Hei! During weekend the linux-next was being broken by introducing a lockdep warning in the console code [ 0.000000] BIOS-e820: [mem 0x00000000e0000000-0x00000000ffffffff] reserved [ 0.000000] [ 0.000000] ============================================= [ 0.000000] [ INFO: possible recursive locking detected ] [ 0.000000] 3.15.0-rc2-next-20140428-00030-gd3550d8 #38 Not tainted [ 0.000000] --------------------------------------------- [ 0.000000] swapper/0 is trying to acquire lock: [ 0.000000] (console_lock){......}, at: [] register_console+0x15e/0x295 [ 0.000000] [ 0.000000] but task is already holding lock: [ 0.000000] (console_lock){......}, at: [] vprintk_emit +0x381/0x3ea [ 0.000000] [ 0.000000] other info that might help us debug this: [ 0.000000] Possible unsafe locking scenario: [ 0.000000] [ 0.000000] CPU0 [ 0.000000] ---- [ 0.000000] lock(console_lock); [ 0.000000] lock(console_lock); [ 0.000000] [ 0.000000] *** DEADLOCK *** [ 0.000000] [ 0.000000] May be due to missing lock nesting notation [ 0.000000] [ 0.000000] 3 locks held by swapper/0: [ 0.000000] #0: (console_lock){......}, at: [] vprintk_emit+0x381/0x3ea [ 0.000000] #1: (console_lock){......}, at: [] vprintk_emit+0x381/0x3ea [ 0.000000] #2: (console_lock){......}, at: [] vprintk_emit+0x381/0x3ea [ 0.000000] [ 0.000000] stack backtrace: [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 3.15.0-rc2-next-20140428-00030-gd3550d8 #38 [ 0.000000] 00000000 00000000 c186de1c c15878ae c1daf840 c186de88 c106c154 c1794d9d [ 0.000000] c17958f7 c1794c9c 0000002a 00000000 00000000 c1daf840 c1983700 00000080 [ 0.000000] 04002001 c187a0b0 00000000 c1879ba0 c1879b40 c1879b40 00200046 00000000 [ 0.000000] Call Trace: [ 0.000000] [] dump_stack+0x49/0x73 [ 0.000000] [] __lock_acquire+0xb31/0xc7c [ 0.000000] [] lock_acquire+0x9c/0x111 [ 0.000000] [] ? register_console+0x15e/0x295 [ 0.000000] [] console_lock+0x41/0x46 [ 0.000000] [] ? register_console+0x15e/0x295 [ 0.000000] [] register_console+0x15e/0x295 [ 0.000000] [] early_console_register+0x33/0x35 [ 0.000000] [] setup_early_printk+0x144/0x151 [ 0.000000] [] do_early_param+0x41/0x73 [ 0.000000] [] ? loglevel+0x2c/0x2c [ 0.000000] [] parse_args+0x24f/0x307 [ 0.000000] [] ? loglevel+0x2c/0x2c [ 0.000000] [] parse_early_options+0x1c/0x21 [ 0.000000] [] ? parse_early_options+0x1c/0x21 [ 0.000000] [] ? loglevel+0x2c/0x2c [ 0.000000] [] parse_early_param+0x2a/0x36 [ 0.000000] [] setup_arch+0x3c9/0xc55 [ 0.000000] [] ? vprintk_emit+0x3c5/0x3ea [ 0.000000] [] ? printk+0x28/0x2d [ 0.000000] [] start_kernel+0x72/0x305 [ 0.000000] [] i386_start_kernel+0x82/0x86 [ 0.000000] bootconsole [earlyhsu0] enabled Bisecting shows the culprit (which I guessed before), namely commit 5dc90cb49691755faaad2a395d297d0162075eca ("printk: enable interrupts before calling console_trylock_for_printk()"). Following patch helps me, but I'm not familiar with console locking scheme, I believe there is a better solution. --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -1700,8 +1700,10 @@ asmlinkage int vprintk_emit(int facility, int level, * The release will print out buffers and wake up /dev/kmsg and syslog() * users. */ + lockdep_off(); if (console_trylock_for_printk()) console_unlock(); + lockdep_on(); preempt_enable(); return printed_len; -- Andy Shevchenko Intel Finland Oy --------------------------------------------------------------------- Intel Finland Oy Registered Address: PL 281, 00181 Helsinki Business Identity Code: 0357606 - 4 Domiciled in Helsinki This e-mail and any attachments may contain confidential material for the sole use of the intended recipient(s). Any review or distribution by others is strictly prohibited. If you are not the intended recipient, please contact the sender and delete all copies. {.n++%ݶw{.n+{G{ayʇڙ,jfhz_(階ݢj"mG?&~iOzv^m ?I