From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757893Ab0EGSlZ (ORCPT ); Fri, 7 May 2010 14:41:25 -0400 Received: from hera.kernel.org ([140.211.167.34]:46392 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757774Ab0EGSlV (ORCPT ); Fri, 7 May 2010 14:41:21 -0400 Date: Fri, 7 May 2010 18:40:59 GMT From: tip-bot for Yong Zhang Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@redhat.com, a.p.zijlstra@chello.nl, davem@davemloft.net, yong.zhang@windriver.com, tglx@linutronix.de, yong.zhang0@windriver.com, mingo@elte.hu Reply-To: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, a.p.zijlstra@chello.nl, davem@davemloft.net, yong.zhang@windriver.com, tglx@linutronix.de, yong.zhang0@windriver.com, mingo@elte.hu In-Reply-To: <20100504065711.GC10784@windriver.com> References: <20100504065711.GC10784@windriver.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:core/locking] lockdep: Reduce stack_trace usage Message-ID: Git-Commit-ID: 4726f2a617ebd868a4fdeb5679613b897e5f1676 X-Mailer: tip-git-log-daemon MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.3 (hera.kernel.org [127.0.0.1]); Fri, 07 May 2010 18:41:02 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 4726f2a617ebd868a4fdeb5679613b897e5f1676 Gitweb: http://git.kernel.org/tip/4726f2a617ebd868a4fdeb5679613b897e5f1676 Author: Yong Zhang AuthorDate: Tue, 4 May 2010 14:16:48 +0800 Committer: Ingo Molnar CommitDate: Fri, 7 May 2010 11:27:26 +0200 lockdep: Reduce stack_trace usage When calling check_prevs_add(), if all validations passed add_lock_to_list() will add new lock to dependency tree and alloc stack_trace for each list_entry. But at this time, we are always on the same stack, so stack_trace for each list_entry has the same value. This is redundant and eats up lots of memory which could lead to warning on low MAX_STACK_TRACE_ENTRIES. Use one copy of stack_trace instead. V2: As suggested by Peter Zijlstra, move save_trace() from check_prevs_add() to check_prev_add(). Add tracking for trylock dependence which is also redundant. Signed-off-by: Yong Zhang Cc: David S. Miller Signed-off-by: Peter Zijlstra LKML-Reference: <20100504065711.GC10784@windriver.com> Signed-off-by: Ingo Molnar --- kernel/lockdep.c | 29 +++++++++++++++++++++-------- 1 files changed, 21 insertions(+), 8 deletions(-) diff --git a/kernel/lockdep.c b/kernel/lockdep.c index 9cf7985..5108080 100644 --- a/kernel/lockdep.c +++ b/kernel/lockdep.c @@ -805,7 +805,8 @@ static struct lock_list *alloc_list_entry(void) * Add a new dependency to the head of the list: */ static int add_lock_to_list(struct lock_class *class, struct lock_class *this, - struct list_head *head, unsigned long ip, int distance) + struct list_head *head, unsigned long ip, + int distance, struct stack_trace *trace) { struct lock_list *entry; /* @@ -816,11 +817,9 @@ static int add_lock_to_list(struct lock_class *class, struct lock_class *this, if (!entry) return 0; - if (!save_trace(&entry->trace)) - return 0; - entry->class = this; entry->distance = distance; + entry->trace = *trace; /* * Since we never remove from the dependency list, the list can * be walked lockless by other CPUs, it's only allocation @@ -1622,12 +1621,20 @@ check_deadlock(struct task_struct *curr, struct held_lock *next, */ static int check_prev_add(struct task_struct *curr, struct held_lock *prev, - struct held_lock *next, int distance) + struct held_lock *next, int distance, int trylock_loop) { struct lock_list *entry; int ret; struct lock_list this; struct lock_list *uninitialized_var(target_entry); + /* + * Static variable, serialized by the graph_lock(). + * + * We use this static variable to save the stack trace in case + * we call into this function multiple times due to encountering + * trylocks in the held lock stack. + */ + static struct stack_trace trace; /* * Prove that the new -> dependency would not @@ -1675,20 +1682,23 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev, } } + if (!trylock_loop && !save_trace(&trace)) + return 0; + /* * Ok, all validations passed, add the new lock * to the previous lock's dependency list: */ ret = add_lock_to_list(hlock_class(prev), hlock_class(next), &hlock_class(prev)->locks_after, - next->acquire_ip, distance); + next->acquire_ip, distance, &trace); if (!ret) return 0; ret = add_lock_to_list(hlock_class(next), hlock_class(prev), &hlock_class(next)->locks_before, - next->acquire_ip, distance); + next->acquire_ip, distance, &trace); if (!ret) return 0; @@ -1718,6 +1728,7 @@ static int check_prevs_add(struct task_struct *curr, struct held_lock *next) { int depth = curr->lockdep_depth; + int trylock_loop = 0; struct held_lock *hlock; /* @@ -1743,7 +1754,8 @@ check_prevs_add(struct task_struct *curr, struct held_lock *next) * added: */ if (hlock->read != 2) { - if (!check_prev_add(curr, hlock, next, distance)) + if (!check_prev_add(curr, hlock, next, + distance, trylock_loop)) return 0; /* * Stop after the first non-trylock entry, @@ -1766,6 +1778,7 @@ check_prevs_add(struct task_struct *curr, struct held_lock *next) if (curr->held_locks[depth].irq_context != curr->held_locks[depth-1].irq_context) break; + trylock_loop = 1; } return 1; out_bug: