[PATCH RT 08/36] rtmutex: Simplify remove_waiter()

Steven Rostedt
2015-03-12T19:34:58Z

[-- Attachment #1: 0008-rtmutex-Simplify-remove_waiter.patch --]
[-- Type: text/plain, Size: 2583 bytes --]

3.12.38-rt53-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Thomas Gleixner <tglx@linutronix.de>

upstream commit: 1ca7b86062ec8473d03c5cdfd336abc8b1c8098c

Exit right away, when the removed waiter was not the top priority
waiter on the lock. Get rid of the extra indent level.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

Conflicts:
kernel/rtmutex.c
---
kernel/rtmutex.c | 33 ++++++++++++++++++---------------
1 file changed, 18 insertions(+), 15 deletions(-)

diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c
index dd1309ed0fa2..215efab038cb 100644
--- a/kernel/rtmutex.c
+++ b/kernel/rtmutex.c
@@ -914,7 +914,7 @@ static void wakeup_next_waiter(struct rt_mutex *lock)
static void remove_waiter(struct rt_mutex *lock,
struct rt_mutex_waiter *waiter)
{
- int first = (waiter == rt_mutex_top_waiter(lock));
+ bool is_top_waiter = (waiter == rt_mutex_top_waiter(lock));
struct task_struct *owner = rt_mutex_owner(lock);
struct rt_mutex *next_lock = NULL;
unsigned long flags;
@@ -924,31 +924,34 @@ static void remove_waiter(struct rt_mutex *lock,
current->pi_blocked_on = NULL;
raw_spin_unlock_irqrestore(&current->pi_lock, flags);

- if (!owner)
+ /*
+ * Only update priority if the waiter was the highest priority
+ * waiter of the lock and there is an owner to update.
+ */
+ if (!owner || !is_top_waiter)
return;

- if (first) {
-
- raw_spin_lock_irqsave(&owner->pi_lock, flags);
+ raw_spin_lock_irqsave(&owner->pi_lock, flags);

- rt_mutex_dequeue_pi(owner, waiter);
+ rt_mutex_dequeue_pi(owner, waiter);

- if (rt_mutex_has_waiters(lock)) {
- struct rt_mutex_waiter *next;
+ if (rt_mutex_has_waiters(lock))
+ rt_mutex_enqueue_pi(owner, rt_mutex_top_waiter(lock));

- next = rt_mutex_top_waiter(lock);
- rt_mutex_enqueue_pi(owner, next);
- }
- __rt_mutex_adjust_prio(owner);
+ __rt_mutex_adjust_prio(owner);

- /* Store the lock on which owner is blocked or NULL */
+ /* Store the lock on which owner is blocked or NULL */
+ if (rt_mutex_real_waiter(owner->pi_blocked_on))
next_lock = task_blocked_on_lock(owner);

- raw_spin_unlock_irqrestore(&owner->pi_lock, flags);
- }
+ raw_spin_unlock_irqrestore(&owner->pi_lock, flags);

WARN_ON(!plist_node_empty(&waiter->pi_list_entry));

+ /*
+ * Don't walk the chain, if the owner task is not blocked
+ * itself.
+ */
if (!next_lock)
return;

--
2.1.4