Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755323AbcDFM7t (ORCPT ); Wed, 6 Apr 2016 08:59:49 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60577 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751827AbcDFM7s (ORCPT ); Wed, 6 Apr 2016 08:59:48 -0400 From: Xunlei Pang To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , Thomas Gleixner , Juri Lelli , Ingo Molnar , Steven Rostedt , Xunlei Pang Subject: [PATCH v2 2/2] rtmutex: Kill pi_waiters_leftmost from task_struct Date: Wed, 6 Apr 2016 20:59:16 +0800 Message-Id: <1459947556-12332-2-git-send-email-xlpang@redhat.com> In-Reply-To: <1459947556-12332-1-git-send-email-xlpang@redhat.com> References: <1459947556-12332-1-git-send-email-xlpang@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3839 Lines: 110 Current code use pi_waiters_leftmost to record the leftmost waiter, but actually it can be get directly from task_struct::pi_waiters using rb_first(). The performance penalty introduced by rb_first() should be fine, because normally there aren't that many rtmutexes chained together for one task. We don't remove rt_mutex:pi_waiters_leftmost, as it is quite possible for many tasks sharing one rtmutex. Thus, hereby remove pi_waiters_leftmost from task_struct. Signed-off-by: Xunlei Pang --- include/linux/init_task.h | 1 - include/linux/sched.h | 1 - kernel/fork.c | 1 - kernel/locking/rtmutex.c | 13 ++----------- kernel/locking/rtmutex_common.h | 2 +- 5 files changed, 3 insertions(+), 15 deletions(-) diff --git a/include/linux/init_task.h b/include/linux/init_task.h index de834f3..a967dbf 100644 --- a/include/linux/init_task.h +++ b/include/linux/init_task.h @@ -162,7 +162,6 @@ extern struct task_group root_task_group; #ifdef CONFIG_RT_MUTEXES # define INIT_RT_MUTEXES(tsk) \ .pi_waiters = RB_ROOT, \ - .pi_waiters_leftmost = NULL, \ .pi_top_task = NULL, #else # define INIT_RT_MUTEXES(tsk) diff --git a/include/linux/sched.h b/include/linux/sched.h index b4d9347..6477e22 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1620,7 +1620,6 @@ struct task_struct { #ifdef CONFIG_RT_MUTEXES /* PI waiters blocked on a rt_mutex held by this task */ struct rb_root pi_waiters; - struct rb_node *pi_waiters_leftmost; struct task_struct *pi_top_task; /* Deadlock detection and priority inheritance handling */ struct rt_mutex_waiter *pi_blocked_on; diff --git a/kernel/fork.c b/kernel/fork.c index 3ad84c9..fc6e5d8 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1207,7 +1207,6 @@ static void rt_mutex_init_task(struct task_struct *p) raw_spin_lock_init(&p->pi_lock); #ifdef CONFIG_RT_MUTEXES p->pi_waiters = RB_ROOT; - p->pi_waiters_leftmost = NULL; p->pi_blocked_on = NULL; p->pi_top_task = NULL; #endif diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c index 6c3a806..b8e9300 100644 --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -223,22 +223,16 @@ rt_mutex_enqueue_pi(struct task_struct *task, struct rt_mutex_waiter *waiter) struct rb_node **link = &task->pi_waiters.rb_node; struct rb_node *parent = NULL; struct rt_mutex_waiter *entry; - int leftmost = 1; while (*link) { parent = *link; entry = rb_entry(parent, struct rt_mutex_waiter, pi_tree_entry); - if (rt_mutex_waiter_less(waiter, entry)) { + if (rt_mutex_waiter_less(waiter, entry)) link = &parent->rb_left; - } else { + else link = &parent->rb_right; - leftmost = 0; - } } - if (leftmost) - task->pi_waiters_leftmost = &waiter->pi_tree_entry; - rb_link_node(&waiter->pi_tree_entry, parent, link); rb_insert_color(&waiter->pi_tree_entry, &task->pi_waiters); } @@ -249,9 +243,6 @@ rt_mutex_dequeue_pi(struct task_struct *task, struct rt_mutex_waiter *waiter) if (RB_EMPTY_NODE(&waiter->pi_tree_entry)) return; - if (task->pi_waiters_leftmost == &waiter->pi_tree_entry) - task->pi_waiters_leftmost = rb_next(&waiter->pi_tree_entry); - rb_erase(&waiter->pi_tree_entry, &task->pi_waiters); RB_CLEAR_NODE(&waiter->pi_tree_entry); } diff --git a/kernel/locking/rtmutex_common.h b/kernel/locking/rtmutex_common.h index 93b0924..ccfa34a 100644 --- a/kernel/locking/rtmutex_common.h +++ b/kernel/locking/rtmutex_common.h @@ -63,7 +63,7 @@ static inline int task_has_pi_waiters(struct task_struct *p) static inline struct rt_mutex_waiter * task_top_pi_waiter(struct task_struct *p) { - return rb_entry(p->pi_waiters_leftmost, struct rt_mutex_waiter, + return rb_entry(rb_first(&p->pi_waiters), struct rt_mutex_waiter, pi_tree_entry); } -- 1.8.3.1