From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756796AbZKRBGj (ORCPT ); Tue, 17 Nov 2009 20:06:39 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756753AbZKRBGi (ORCPT ); Tue, 17 Nov 2009 20:06:38 -0500 Received: from ey-out-2122.google.com ([74.125.78.26]:6829 "EHLO ey-out-2122.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756751AbZKRBGg (ORCPT ); Tue, 17 Nov 2009 20:06:36 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=from:to:cc:subject:date:message-id:x-mailer:in-reply-to:references; b=Vo4v66vjXEcu+BWCURGLqHggJleuKTQFxO/9TB1w6s3ewESBerZjOVPsNan+BXxiE7 oHraAAmeCUXwC/TM39VNCdN1YRC5WXgiVlzndZZ1d/XRJ59cm9OYTUt0JBYgnm7JCX0k d+5BwZi8GYdHxEs6dEmj2o+txOiyRqFnyEnGI= From: Frederic Weisbecker To: Ingo Molnar Cc: LKML , Frederic Weisbecker , Peter Zijlstra , Thomas Gleixner , Ming Lei Subject: [PATCH 2/2] lockdep: Don't only check recursive read locks once in a sequence Date: Wed, 18 Nov 2009 02:06:38 +0100 Message-Id: <1258506398-5151-3-git-send-email-fweisbec@gmail.com> X-Mailer: git-send-email 1.6.2.3 In-Reply-To: <1258506398-5151-1-git-send-email-fweisbec@gmail.com> References: <1258506398-5151-1-git-send-email-fweisbec@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Say we have the following locks: A (rwlock, Aw: writelock, Ar: recursive read lock) B (normal lock) and the following sequences: Ar -> B -> Ar Aw -> B This won't be detected as a lock inversion because in the sequence of locks held by the current task, if we have a same class acquired as read-recursive several times, only the first one will be checked in the tree (although all of them are checked for deadlocks in the current held sequence). Fix it by always adding recursive read locks in the dependency tree. Signed-off-by: Frederic Weisbecker Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Ming Lei --- kernel/lockdep.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/lockdep.c b/kernel/lockdep.c index a6f7440..13d1d54 100644 --- a/kernel/lockdep.c +++ b/kernel/lockdep.c @@ -1949,9 +1949,9 @@ static int validate_chain(struct task_struct *curr, struct lockdep_map *lock, hlock->read = 2; /* * Add dependency only if this lock is not the head - * of the chain, and if it's not a secondary read-lock: + * of the chain. */ - if (!chain_head && ret != 2) + if (!chain_head) if (!check_prevs_add(curr, hlock)) return 0; graph_unlock(); -- 1.6.2.3