From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753806AbaBJNeI (ORCPT ); Mon, 10 Feb 2014 08:34:08 -0500 Received: from terminus.zytor.com ([198.137.202.10]:33387 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753104AbaBJNeA (ORCPT ); Mon, 10 Feb 2014 08:34:00 -0500 Date: Mon, 10 Feb 2014 05:33:08 -0800 From: tip-bot for Oleg Nesterov Message-ID: Cc: linux-kernel@vger.kernel.org, sasha.levin@oracle.com, hpa@zytor.com, mingo@kernel.org, stern@rowland.harvard.edu, torvalds@linux-foundation.org, peterz@infradead.org, davej@redhat.com, gregkh@linuxfoundation.org, paulmck@linux.vnet.ibm.com, rostedt@goodmis.org, tglx@linutronix.de, oleg@redhat.com Reply-To: mingo@kernel.org, hpa@zytor.com, sasha.levin@oracle.com, linux-kernel@vger.kernel.org, stern@rowland.harvard.edu, torvalds@linux-foundation.org, peterz@infradead.org, davej@redhat.com, paulmck@linux.vnet.ibm.com, gregkh@linuxfoundation.org, rostedt@goodmis.org, oleg@redhat.com, tglx@linutronix.de In-Reply-To: <20140120182010.GA26498@redhat.com> References: <20140120182010.GA26498@redhat.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:core/locking] lockdep: Don' t create the wrong dependency on hlock->check == 0 Git-Commit-ID: 1b5ff816cab708ba44c7d7b56b613516269eb577 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.1 (terminus.zytor.com [127.0.0.1]); Mon, 10 Feb 2014 05:33:15 -0800 (PST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 1b5ff816cab708ba44c7d7b56b613516269eb577 Gitweb: http://git.kernel.org/tip/1b5ff816cab708ba44c7d7b56b613516269eb577 Author: Oleg Nesterov AuthorDate: Mon, 20 Jan 2014 19:20:10 +0100 Committer: Ingo Molnar CommitDate: Sun, 9 Feb 2014 21:18:57 +0100 lockdep: Don't create the wrong dependency on hlock->check == 0 Test-case: DEFINE_MUTEX(m1); DEFINE_MUTEX(m2); DEFINE_MUTEX(mx); void lockdep_should_complain(void) { lockdep_set_novalidate_class(&mx); // m1 -> mx -> m2 mutex_lock(&m1); mutex_lock(&mx); mutex_lock(&m2); mutex_unlock(&m2); mutex_unlock(&mx); mutex_unlock(&m1); // m2 -> m1 ; should trigger the warning mutex_lock(&m2); mutex_lock(&m1); mutex_unlock(&m1); mutex_unlock(&m2); } this doesn't trigger any warning, lockdep can't detect the trivial deadlock. This is because lock(&mx) correctly avoids m1 -> mx dependency, it skips validate_chain() due to mx->check == 0. But lock(&m2) wrongly adds mx -> m2 and thus m1 -> m2 is not created. rcu_lock_acquire()->lock_acquire(check => 0) is fine due to read == 2, so currently only __lockdep_no_validate__ can trigger this problem. Signed-off-by: Oleg Nesterov Cc: Dave Jones Cc: Greg Kroah-Hartman Cc: Linus Torvalds Cc: Paul McKenney Cc: Steven Rostedt Cc: Alan Stern Cc: Sasha Levin Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/20140120182010.GA26498@redhat.com Signed-off-by: Ingo Molnar --- kernel/locking/lockdep.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 8c85a0d..f7eba92 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -1936,12 +1936,12 @@ check_prevs_add(struct task_struct *curr, struct held_lock *next) for (;;) { int distance = curr->lockdep_depth - depth + 1; - hlock = curr->held_locks + depth-1; + hlock = curr->held_locks + depth - 1; /* * Only non-recursive-read entries get new dependencies * added: */ - if (hlock->read != 2) { + if (hlock->read != 2 && hlock->check) { if (!check_prev_add(curr, hlock, next, distance, trylock_loop)) return 0;