From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753923Ab1DVMUx (ORCPT ); Fri, 22 Apr 2011 08:20:53 -0400 Received: from hera.kernel.org ([140.211.167.34]:57038 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753446Ab1DVMUv (ORCPT ); Fri, 22 Apr 2011 08:20:51 -0400 Date: Fri, 22 Apr 2011 12:20:29 GMT From: tip-bot for Steven Rostedt Message-ID: Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@redhat.com, torvalds@linux-foundation.org, a.p.zijlstra@chello.nl, fweisbec@gmail.com, akpm@linux-foundation.org, rostedt@goodmis.org, srostedt@redhat.com, tglx@linutronix.de, mingo@elte.hu Reply-To: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, a.p.zijlstra@chello.nl, torvalds@linux-foundation.org, fweisbec@gmail.com, akpm@linux-foundation.org, rostedt@goodmis.org, srostedt@redhat.com, tglx@linutronix.de, mingo@elte.hu In-Reply-To: <20110421014259.643930104@goodmis.org> References: <20110421014259.643930104@goodmis.org> To: linux-tip-commits@vger.kernel.org Subject: [tip:core/locking] lockdep: Print a nicer description for simple deadlocks Git-Commit-ID: 48702ecf308e53f176c1f6fdc193d622ded54ac0 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.3 (hera.kernel.org [127.0.0.1]); Fri, 22 Apr 2011 12:20:29 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 48702ecf308e53f176c1f6fdc193d622ded54ac0 Gitweb: http://git.kernel.org/tip/48702ecf308e53f176c1f6fdc193d622ded54ac0 Author: Steven Rostedt AuthorDate: Wed, 20 Apr 2011 21:41:56 -0400 Committer: Ingo Molnar CommitDate: Fri, 22 Apr 2011 11:06:58 +0200 lockdep: Print a nicer description for simple deadlocks Lockdep output can be pretty cryptic, having nicer output can save a lot of head scratching. When a simple deadlock scenario is detected by lockdep (lock A -> lock A) we now get the following new output: other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&(lock)->rlock); lock(&(lock)->rlock); *** DEADLOCK *** Signed-off-by: Steven Rostedt Acked-by: Peter Zijlstra Cc: Frederic Weisbecker Cc: Linus Torvalds Cc: Andrew Morton Link: http://lkml.kernel.org/r/20110421014259.643930104@goodmis.org Signed-off-by: Ingo Molnar --- kernel/lockdep.c | 21 +++++++++++++++++++++ 1 files changed, 21 insertions(+), 0 deletions(-) diff --git a/kernel/lockdep.c b/kernel/lockdep.c index 73cebd7..c4cc5d1 100644 --- a/kernel/lockdep.c +++ b/kernel/lockdep.c @@ -1664,6 +1664,26 @@ static inline void inc_chains(void) #endif +static void +print_deadlock_scenario(struct held_lock *nxt, + struct held_lock *prv) +{ + struct lock_class *next = hlock_class(nxt); + struct lock_class *prev = hlock_class(prv); + + printk(" Possible unsafe locking scenario:\n\n"); + printk(" CPU0\n"); + printk(" ----\n"); + printk(" lock("); + __print_lock_name(prev); + printk(");\n"); + printk(" lock("); + __print_lock_name(next); + printk(");\n"); + printk("\n *** DEADLOCK ***\n\n"); + printk(" May be due to missing lock nesting notation\n\n"); +} + static int print_deadlock_bug(struct task_struct *curr, struct held_lock *prev, struct held_lock *next) @@ -1682,6 +1702,7 @@ print_deadlock_bug(struct task_struct *curr, struct held_lock *prev, print_lock(prev); printk("\nother info that might help us debug this:\n"); + print_deadlock_scenario(next, prev); lockdep_print_held_locks(curr); printk("\nstack backtrace:\n");