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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 E3C31C10F14 for ; Thu, 18 Apr 2019 09:08:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B7DD62184B for ; Thu, 18 Apr 2019 09:08:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388696AbfDRJIG (ORCPT ); Thu, 18 Apr 2019 05:08:06 -0400 Received: from Galois.linutronix.de ([146.0.238.70]:34157 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388674AbfDRJIE (ORCPT ); Thu, 18 Apr 2019 05:08:04 -0400 Received: from localhost ([127.0.0.1] helo=nanos.tec.linutronix.de) by Galois.linutronix.de with esmtp (Exim 4.80) (envelope-from ) id 1hH309-0001su-Qw; Thu, 18 Apr 2019 11:06:38 +0200 Message-Id: <20190418084254.729689921@linutronix.de> User-Agent: quilt/0.65 Date: Thu, 18 Apr 2019 10:41:37 +0200 From: Thomas Gleixner To: LKML Cc: Josh Poimboeuf , x86@kernel.org, Andy Lutomirski , Steven Rostedt , Alexander Potapenko , Alexey Dobriyan , Andrew Morton , Pekka Enberg , linux-mm@kvack.org, David Rientjes , Christoph Lameter , Catalin Marinas , Dmitry Vyukov , Andrey Ryabinin , kasan-dev@googlegroups.com, Mike Rapoport , Akinobu Mita , iommu@lists.linux-foundation.org, Robin Murphy , Christoph Hellwig , Marek Szyprowski , Johannes Thumshirn , David Sterba , Chris Mason , Josef Bacik , linux-btrfs@vger.kernel.org, dm-devel@redhat.com, Mike Snitzer , Alasdair Kergon , intel-gfx@lists.freedesktop.org, Joonas Lahtinen , Maarten Lankhorst , dri-devel@lists.freedesktop.org, David Airlie , Jani Nikula , Daniel Vetter , Rodrigo Vivi , linux-arch@vger.kernel.org Subject: [patch V2 18/29] lockdep: Move stack trace logic into check_prev_add() References: <20190418084119.056416939@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There is only one caller of check_prev_add() which hands in a zeroed struct stack trace and a function pointer to save_stack(). Inside check_prev_add() the stack_trace struct is checked for being empty, which is always true. Based on that one code path stores a stack trace which is unused. The comment there does not make sense either. It's all leftovers from historical lockdep code (cross release). Move the variable into check_prev_add() itself and cleanup the nonsensical checks and the pointless stack trace recording. Signed-off-by: Thomas Gleixner --- kernel/locking/lockdep.c | 30 ++++++++---------------------- 1 file changed, 8 insertions(+), 22 deletions(-) --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -2158,10 +2158,10 @@ check_deadlock(struct task_struct *curr, */ static int check_prev_add(struct task_struct *curr, struct held_lock *prev, - struct held_lock *next, int distance, struct stack_trace *trace, - int (*save)(struct stack_trace *trace)) + struct held_lock *next, int distance) { struct lock_list *uninitialized_var(target_entry); + struct stack_trace trace; struct lock_list *entry; struct lock_list this; int ret; @@ -2196,17 +2196,8 @@ check_prev_add(struct task_struct *curr, this.class = hlock_class(next); this.parent = NULL; ret = check_noncircular(&this, hlock_class(prev), &target_entry); - if (unlikely(!ret)) { - if (!trace->entries) { - /* - * If @save fails here, the printing might trigger - * a WARN but because of the !nr_entries it should - * not do bad things. - */ - save(trace); - } + if (unlikely(!ret)) return print_circular_bug(&this, target_entry, next, prev); - } else if (unlikely(ret < 0)) return print_bfs_bug(ret); @@ -2253,7 +2244,7 @@ check_prev_add(struct task_struct *curr, return print_bfs_bug(ret); - if (!trace->entries && !save(trace)) + if (!save_trace(&trace)) return 0; /* @@ -2262,14 +2253,14 @@ check_prev_add(struct task_struct *curr, */ ret = add_lock_to_list(hlock_class(next), hlock_class(prev), &hlock_class(prev)->locks_after, - next->acquire_ip, distance, trace); + next->acquire_ip, distance, &trace); if (!ret) return 0; ret = add_lock_to_list(hlock_class(prev), hlock_class(next), &hlock_class(next)->locks_before, - next->acquire_ip, distance, trace); + next->acquire_ip, distance, &trace); if (!ret) return 0; @@ -2287,12 +2278,6 @@ check_prevs_add(struct task_struct *curr { int depth = curr->lockdep_depth; struct held_lock *hlock; - struct stack_trace trace = { - .nr_entries = 0, - .max_entries = 0, - .entries = NULL, - .skip = 0, - }; /* * Debugging checks. @@ -2318,7 +2303,8 @@ check_prevs_add(struct task_struct *curr * added: */ if (hlock->read != 2 && hlock->check) { - int ret = check_prev_add(curr, hlock, next, distance, &trace, save_trace); + int ret = check_prev_add(curr, hlock, next, distance); + if (!ret) return 0;