From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 455CAC072B5 for ; Fri, 24 May 2019 20:15:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 243FE2133D for ; Fri, 24 May 2019 20:15:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391814AbfEXUPt (ORCPT ); Fri, 24 May 2019 16:15:49 -0400 Received: from mga04.intel.com ([192.55.52.120]:33088 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391738AbfEXUPr (ORCPT ); Fri, 24 May 2019 16:15:47 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga003.jf.intel.com ([10.7.209.27]) by fmsmga104.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 24 May 2019 13:15:46 -0700 X-ExtLoop1: 1 Received: from ideak-desk.fi.intel.com ([10.237.72.204]) by orsmga003.jf.intel.com with ESMTP; 24 May 2019 13:15:44 -0700 From: Imre Deak To: LKML Cc: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= , Peter Zijlstra , Ingo Molnar , Will Deacon Subject: [PATCH v2 2/2] lockdep: Fix merging of hlocks with non-zero references Date: Fri, 24 May 2019 23:15:09 +0300 Message-Id: <20190524201509.9199-2-imre.deak@intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190524201509.9199-1-imre.deak@intel.com> References: <20190524201509.9199-1-imre.deak@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The sequence static DEFINE_WW_CLASS(test_ww_class); struct ww_acquire_ctx ww_ctx; struct ww_mutex ww_lock_a; struct ww_mutex ww_lock_b; struct ww_mutex ww_lock_c; struct mutex lock_c; ww_acquire_init(&ww_ctx, &test_ww_class); ww_mutex_init(&ww_lock_a, &test_ww_class); ww_mutex_init(&ww_lock_b, &test_ww_class); ww_mutex_init(&ww_lock_c, &test_ww_class); mutex_init(&lock_c); ww_mutex_lock(&ww_lock_a, &ww_ctx); mutex_lock(&lock_c); ww_mutex_lock(&ww_lock_b, &ww_ctx); ww_mutex_lock(&ww_lock_c, &ww_ctx); mutex_unlock(&lock_c); (*) ww_mutex_unlock(&ww_lock_c); ww_mutex_unlock(&ww_lock_b); ww_mutex_unlock(&ww_lock_a); ww_acquire_fini(&ww_ctx); (**) will trigger the following error in __lock_release() when calling mutex_release() at **: DEBUG_LOCKS_WARN_ON(depth <= 0) The problem is that the hlock merging happening at * updates the references for test_ww_class incorrectly to 3 whereas it should've updated it to 4 (representing all the instances for ww_ctx and ww_lock_[abc]). Fix this by updating the references during merging correctly taking into account that we can have non-zero references (both for the hlock that we merge into another hlock or for the hlock we are merging into). Cc: Ville Syrjälä Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Will Deacon Signed-off-by: Imre Deak --- kernel/locking/lockdep.c | 23 +++++++++++++---------- 1 file changed, 13 insertions(+), 10 deletions(-) diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 967352d32af1..9e2a4ab6c731 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -3637,6 +3637,11 @@ print_lock_nested_lock_not_held(struct task_struct *curr, static int __lock_is_held(const struct lockdep_map *lock, int read); +static int hlock_reference(int reference) +{ + return reference ? : 1; +} + /* * This gets called for every mutex_lock*()/spin_lock*() operation. * We maintain the dependency maps and validate the locking attempt: @@ -3702,17 +3707,15 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass, if (depth) { hlock = curr->held_locks + depth - 1; if (hlock->class_idx == class_idx && nest_lock) { - if (hlock->references) { - /* - * Check: unsigned int references overflow. - */ - if (DEBUG_LOCKS_WARN_ON(hlock->references == UINT_MAX)) - return 0; + /* + * Check: unsigned int references overflow. + */ + if (DEBUG_LOCKS_WARN_ON(hlock_reference(hlock->references) > + UINT_MAX - hlock_reference(references))) + return 0; - hlock->references++; - } else { - hlock->references = 2; - } + hlock->references = hlock_reference(hlock->references) + + hlock_reference(references); return 2; } -- 2.17.1