From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754522AbbJSTas (ORCPT ); Mon, 19 Oct 2015 15:30:48 -0400 Received: from mail-lf0-f50.google.com ([209.85.215.50]:35548 "EHLO mail-lf0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752402AbbJSTaq (ORCPT ); Mon, 19 Oct 2015 15:30:46 -0400 From: j.glisse@gmail.com To: linux-kernel@vger.kernel.org Cc: =?UTF-8?q?J=C3=A9r=C3=B4me=20Glisse?= , Ingo Molnar , Peter Zijlstra , Sasha Levin Subject: [PATCH] locking/lockdep: Fix expected depth value in __lock_release() Date: Mon, 19 Oct 2015 15:30:28 -0400 Message-Id: <1445283028-7865-1-git-send-email-j.glisse@gmail.com> X-Mailer: git-send-email 1.8.3.1 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Jérôme Glisse In __lock_release() we are removing one entry from the stack and rebuilding the hash chain by re-adding entry above the entry we just removed. If the entry removed was between 2 entry of same class then this 2 entry might be coalesced into one single entry which in turns means that the lockdep_depth value will not be incremented and thus the expected lockdep_depth value after this operation will be wrong triggering an unjustified WARN_ONCE() at the end of __lock_release(). This patch adjust the expect depth value by decrementing it if what was previously 2 entry inside the stack are coalesced into only one entry. Note that __lock_set_class() does not suffer from same issue as it adds a new class and thus can not lead to coalescing of stack entry. Signed-off-by: Jérôme Glisse Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Sasha Levin --- kernel/locking/lockdep.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 4e49cc4..cac5e21 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -3428,6 +3428,8 @@ found_it: curr->curr_chain_key = hlock->prev_chain_key; for (i++; i < depth; i++) { + int tmp = curr->lockdep_depth; + hlock = curr->held_locks + i; if (!__lock_acquire(hlock->instance, hlock_class(hlock)->subclass, hlock->trylock, @@ -3435,6 +3437,13 @@ found_it: hlock->nest_lock, hlock->acquire_ip, hlock->references, hlock->pin_count)) return 0; + /* + * If nest_lock is true and the lock we just removed allow two + * lock of same class to be consolidated in only one held_lock + * then the lockdep_depth count will not increase as we expect + * it to. So adjust the expected depth value accordingly. + */ + depth -= (curr->lockdep_depth == tmp); } /* -- 1.8.3.1