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=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 F253BC10F11 for ; Wed, 10 Apr 2019 11:06:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CCB80218D2 for ; Wed, 10 Apr 2019 11:06:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731187AbfDJLGS (ORCPT ); Wed, 10 Apr 2019 07:06:18 -0400 Received: from Galois.linutronix.de ([146.0.238.70]:58975 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731125AbfDJLGP (ORCPT ); Wed, 10 Apr 2019 07:06:15 -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 1hEB3V-0005EJ-ML; Wed, 10 Apr 2019 13:06:13 +0200 Message-Id: <20190410103646.667572056@linutronix.de> User-Agent: quilt/0.65 Date: Wed, 10 Apr 2019 12:28:28 +0200 From: Thomas Gleixner To: LKML Cc: Josh Poimboeuf , x86@kernel.org, Andy Lutomirski , Steven Rostedt , Alexander Potapenko Subject: [RFC patch 34/41] lockdep: Move stack trace logic into check_prev_add() References: <20190410102754.387743324@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. 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;