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From: Davidlohr Bueso <dave@stgolabs.net>
To: akpm@linux-foundation.org
Cc: mingo@kernel.org, peterz@infradead.org, jack@suse.cz,
	torvalds@linux-foundation.org, kirill.shutemov@linux.intel.com,
	hch@infradead.org, ldufour@linux.vnet.ibm.com, mhocko@suse.com,
	mgorman@techsingularity.net, dave@stgolabs.net,
	linux-kernel@vger.kernel.org, Davidlohr Bueso <dbueso@suse.de>
Subject: [PATCH 09/17] locking/rtmutex: replace top-waiter and pi_waiters leftmost caching
Date: Tue, 18 Jul 2017 18:45:55 -0700
Message-ID: <20170719014603.19029-10-dave@stgolabs.net> (raw)
In-Reply-To: <20170719014603.19029-1-dave@stgolabs.net>

... with the generic rbtree flavor instead. No changes
in semantics whatsoever.

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
---
 include/linux/init_task.h       |  5 ++---
 include/linux/rtmutex.h         | 11 +++++------
 include/linux/sched.h           |  3 +--
 kernel/fork.c                   |  3 +--
 kernel/locking/rtmutex-debug.c  |  2 +-
 kernel/locking/rtmutex.c        | 35 +++++++++++------------------------
 kernel/locking/rtmutex_common.h | 12 ++++++------
 7 files changed, 27 insertions(+), 44 deletions(-)

diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index a2f6707e9fc0..2008de121705 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -181,9 +181,8 @@ extern struct cred init_cred;
 
 #ifdef CONFIG_RT_MUTEXES
 # define INIT_RT_MUTEXES(tsk)						\
-	.pi_waiters = RB_ROOT,						\
-	.pi_top_task = NULL,						\
-	.pi_waiters_leftmost = NULL,
+	.pi_waiters = RB_ROOT_CACHED,					\
+	.pi_top_task = NULL,
 #else
 # define INIT_RT_MUTEXES(tsk)
 #endif
diff --git a/include/linux/rtmutex.h b/include/linux/rtmutex.h
index 44fd002f7cd5..53fcbe9de7fd 100644
--- a/include/linux/rtmutex.h
+++ b/include/linux/rtmutex.h
@@ -22,18 +22,17 @@ extern int max_lock_depth; /* for sysctl */
  * The rt_mutex structure
  *
  * @wait_lock:	spinlock to protect the structure
- * @waiters:	rbtree root to enqueue waiters in priority order
- * @waiters_leftmost: top waiter
+ * @waiters:	rbtree root to enqueue waiters in priority order;
+ *              caches top-waiter (leftmost node).
  * @owner:	the mutex owner
  */
 struct rt_mutex {
 	raw_spinlock_t		wait_lock;
-	struct rb_root          waiters;
-	struct rb_node          *waiters_leftmost;
+	struct rb_root_cached   waiters;
 	struct task_struct	*owner;
 #ifdef CONFIG_DEBUG_RT_MUTEXES
 	int			save_state;
-	const char 		*name, *file;
+	const char		*name, *file;
 	int			line;
 	void			*magic;
 #endif
@@ -84,7 +83,7 @@ do { \
 
 #define __RT_MUTEX_INITIALIZER(mutexname) \
 	{ .wait_lock = __RAW_SPIN_LOCK_UNLOCKED(mutexname.wait_lock) \
-	, .waiters = RB_ROOT \
+	, .waiters = RB_ROOT_CACHED \
 	, .owner = NULL \
 	__DEBUG_RT_MUTEX_INITIALIZER(mutexname) \
 	__DEP_MAP_RT_MUTEX_INITIALIZER(mutexname)}
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 8337e2db0bb2..99753c3e470d 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -811,8 +811,7 @@ 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 rb_root_cached		pi_waiters;
 	/* Updated under owner's pi_lock and rq lock */
 	struct task_struct		*pi_top_task;
 	/* Deadlock detection and priority inheritance handling: */
diff --git a/kernel/fork.c b/kernel/fork.c
index 17921b0390b4..4235905fe9d1 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1458,8 +1458,7 @@ 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_waiters = RB_ROOT_CACHED;
 	p->pi_top_task = NULL;
 	p->pi_blocked_on = NULL;
 #endif
diff --git a/kernel/locking/rtmutex-debug.c b/kernel/locking/rtmutex-debug.c
index ac35e648b0e5..f4a74e78d467 100644
--- a/kernel/locking/rtmutex-debug.c
+++ b/kernel/locking/rtmutex-debug.c
@@ -58,7 +58,7 @@ static void printk_lock(struct rt_mutex *lock, int print_owner)
 
 void rt_mutex_debug_task_free(struct task_struct *task)
 {
-	DEBUG_LOCKS_WARN_ON(!RB_EMPTY_ROOT(&task->pi_waiters));
+	DEBUG_LOCKS_WARN_ON(!RB_EMPTY_ROOT(&task->pi_waiters.rb_root));
 	DEBUG_LOCKS_WARN_ON(task->pi_blocked_on);
 }
 
diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index 649dc9d3951a..6f3dba6e4e9e 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -271,10 +271,10 @@ rt_mutex_waiter_equal(struct rt_mutex_waiter *left,
 static void
 rt_mutex_enqueue(struct rt_mutex *lock, struct rt_mutex_waiter *waiter)
 {
-	struct rb_node **link = &lock->waiters.rb_node;
+	struct rb_node **link = &lock->waiters.rb_root.rb_node;
 	struct rb_node *parent = NULL;
 	struct rt_mutex_waiter *entry;
-	int leftmost = 1;
+	bool leftmost = true;
 
 	while (*link) {
 		parent = *link;
@@ -283,15 +283,12 @@ rt_mutex_enqueue(struct rt_mutex *lock, struct rt_mutex_waiter *waiter)
 			link = &parent->rb_left;
 		} else {
 			link = &parent->rb_right;
-			leftmost = 0;
+			leftmost = false;
 		}
 	}
 
-	if (leftmost)
-		lock->waiters_leftmost = &waiter->tree_entry;
-
 	rb_link_node(&waiter->tree_entry, parent, link);
-	rb_insert_color(&waiter->tree_entry, &lock->waiters);
+	rb_insert_color_cached(&waiter->tree_entry, &lock->waiters, leftmost);
 }
 
 static void
@@ -300,20 +297,17 @@ rt_mutex_dequeue(struct rt_mutex *lock, struct rt_mutex_waiter *waiter)
 	if (RB_EMPTY_NODE(&waiter->tree_entry))
 		return;
 
-	if (lock->waiters_leftmost == &waiter->tree_entry)
-		lock->waiters_leftmost = rb_next(&waiter->tree_entry);
-
-	rb_erase(&waiter->tree_entry, &lock->waiters);
+	rb_erase_cached(&waiter->tree_entry, &lock->waiters);
 	RB_CLEAR_NODE(&waiter->tree_entry);
 }
 
 static void
 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 **link = &task->pi_waiters.rb_root.rb_node;
 	struct rb_node *parent = NULL;
 	struct rt_mutex_waiter *entry;
-	int leftmost = 1;
+	bool leftmost = true;
 
 	while (*link) {
 		parent = *link;
@@ -322,15 +316,12 @@ rt_mutex_enqueue_pi(struct task_struct *task, struct rt_mutex_waiter *waiter)
 			link = &parent->rb_left;
 		} else {
 			link = &parent->rb_right;
-			leftmost = 0;
+			leftmost = false;
 		}
 	}
 
-	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);
+	rb_insert_color_cached(&waiter->pi_tree_entry, &task->pi_waiters, leftmost);
 }
 
 static void
@@ -339,10 +330,7 @@ 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_erase_cached(&waiter->pi_tree_entry, &task->pi_waiters);
 	RB_CLEAR_NODE(&waiter->pi_tree_entry);
 }
 
@@ -1657,8 +1645,7 @@ void __rt_mutex_init(struct rt_mutex *lock, const char *name,
 {
 	lock->owner = NULL;
 	raw_spin_lock_init(&lock->wait_lock);
-	lock->waiters = RB_ROOT;
-	lock->waiters_leftmost = NULL;
+	lock->waiters = RB_ROOT_CACHED;
 
 	if (name && key)
 		debug_rt_mutex_init(lock, name, key);
diff --git a/kernel/locking/rtmutex_common.h b/kernel/locking/rtmutex_common.h
index 72ad45a9a794..524beeee24b0 100644
--- a/kernel/locking/rtmutex_common.h
+++ b/kernel/locking/rtmutex_common.h
@@ -42,7 +42,7 @@ struct rt_mutex_waiter {
  */
 static inline int rt_mutex_has_waiters(struct rt_mutex *lock)
 {
-	return !RB_EMPTY_ROOT(&lock->waiters);
+	return !RB_EMPTY_ROOT(&lock->waiters.rb_root);
 }
 
 static inline struct rt_mutex_waiter *
@@ -50,8 +50,8 @@ rt_mutex_top_waiter(struct rt_mutex *lock)
 {
 	struct rt_mutex_waiter *w;
 
-	w = rb_entry(lock->waiters_leftmost, struct rt_mutex_waiter,
-		     tree_entry);
+	w = rb_entry(lock->waiters.rb_leftmost,
+		     struct rt_mutex_waiter, tree_entry);
 	BUG_ON(w->lock != lock);
 
 	return w;
@@ -59,14 +59,14 @@ rt_mutex_top_waiter(struct rt_mutex *lock)
 
 static inline int task_has_pi_waiters(struct task_struct *p)
 {
-	return !RB_EMPTY_ROOT(&p->pi_waiters);
+	return !RB_EMPTY_ROOT(&p->pi_waiters.rb_root);
 }
 
 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,
-			pi_tree_entry);
+	return rb_entry(p->pi_waiters.rb_leftmost,
+			struct rt_mutex_waiter, pi_tree_entry);
 }
 
 /*
-- 
2.12.0

  parent reply index

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-07-19  1:45 [PATCH -next v4 00/17] rbtree: cache leftmost node internally Davidlohr Bueso
2017-07-19  1:45 ` [PATCH 01/17] " Davidlohr Bueso
2017-07-19  1:45 ` [PATCH 02/17] rbtree: optimize root-check during rebalancing loop Davidlohr Bueso
2017-07-19  1:45 ` [PATCH 03/17] rbtree: add some additional comments for rebalancing cases Davidlohr Bueso
2017-07-19  1:45 ` [PATCH 04/17] lib/rbtree_test.c: make input module parameters Davidlohr Bueso
2017-07-19  1:45 ` [PATCH 05/17] lib/rbtree_test.c: add (inorder) traversal test Davidlohr Bueso
2017-07-19  1:45 ` [PATCH 06/17] lib/rbtree_test.c: support rb_root_cached Davidlohr Bueso
2017-07-19  1:45 ` [PATCH 07/17] sched/fair: replace cfs_rq->rb_leftmost Davidlohr Bueso
2017-07-19  1:45 ` [PATCH 08/17] sched/deadline: replace earliest dl and rq leftmost caching Davidlohr Bueso
2017-07-19  1:45 ` Davidlohr Bueso [this message]
2017-07-19  1:45 ` [PATCH 10/17] block/cfq: replace cfq_rb_root " Davidlohr Bueso
2017-07-19  7:46   ` Jan Kara
2017-07-19  1:45 ` [PATCH 11/17] lib/interval_tree: fast overlap detection Davidlohr Bueso
2017-07-22 17:52   ` Doug Ledford
2017-08-01 17:16   ` Michael S. Tsirkin
2017-07-19  1:45 ` [PATCH 12/17] lib/interval-tree: correct comment wrt generic flavor Davidlohr Bueso
2017-07-19  1:45 ` [PATCH 13/17] procfs: use faster rb_first_cached() Davidlohr Bueso
2017-07-19  1:46 ` [PATCH 14/17] fs/epoll: " Davidlohr Bueso
2017-07-19  1:46 ` [PATCH 15/17] fs/ext4: use cached rbtrees Davidlohr Bueso
2017-07-19  7:40   ` Jan Kara
2017-07-19 22:50     ` Davidlohr Bueso
2017-07-19  1:46 ` [PATCH 16/17] mem/memcg: cache rightmost node Davidlohr Bueso
2017-07-19  7:50   ` Michal Hocko
2017-07-26 21:09     ` Andrew Morton
2017-07-27  7:06       ` Michal Hocko
2017-07-19  1:46 ` [PATCH 17/17] block/cfq: cache rightmost rb_node Davidlohr Bueso
2017-07-19  7:59   ` Jan Kara

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