| From 735d5151fa32358753d9b05add1eb1bf5f7a656b Mon Sep 17 00:00:00 2001 |
| From: Gregory Haskins <ghaskins@novell.com> |
| Date: Fri, 3 Jul 2009 08:44:22 -0500 |
| Subject: [PATCH] rtmutex: Adjust pi_lock usage in wakeup |
| |
| commit 26ba8e4b70af50b0049ff964f9366a56f7f60293 in tip. |
| |
| [ The following text is in the "utf-8" character set. ] |
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| |
| From: Peter W.Morreale <pmorreale@novell.com> |
| |
| In wakeup_next_waiter(), we take the pi_lock, and then find out whether |
| we have another waiter to add to the pending owner. We can reduce |
| contention on the pi_lock for the pending owner if we first obtain the |
| pointer to the next waiter outside of the pi_lock. |
| |
| Signed-off-by: Peter W. Morreale <pmorreale@novell.com> |
| Signed-off-by: Gregory Haskins <ghaskins@novell.com> |
| Signed-off-by: Ingo Molnar <mingo@elte.hu> |
| Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |
| |
| diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c |
| index 6435b54..5017ecb 100644 |
| --- a/kernel/rtmutex.c |
| +++ b/kernel/rtmutex.c |
| @@ -507,6 +507,7 @@ static void wakeup_next_waiter(struct rt_mutex *lock, int savestate) |
| { |
| struct rt_mutex_waiter *waiter; |
| struct task_struct *pendowner; |
| + struct rt_mutex_waiter *next; |
| |
| raw_spin_lock(¤t->pi_lock); |
| |
| @@ -569,6 +570,12 @@ static void wakeup_next_waiter(struct rt_mutex *lock, int savestate) |
| * waiter with higher priority than pending-owner->normal_prio |
| * is blocked on the unboosted (pending) owner. |
| */ |
| + |
| + if (rt_mutex_has_waiters(lock)) |
| + next = rt_mutex_top_waiter(lock); |
| + else |
| + next = NULL; |
| + |
| raw_spin_lock(&pendowner->pi_lock); |
| |
| WARN_ON(!pendowner->pi_blocked_on); |
| @@ -577,12 +584,9 @@ static void wakeup_next_waiter(struct rt_mutex *lock, int savestate) |
| |
| pendowner->pi_blocked_on = NULL; |
| |
| - if (rt_mutex_has_waiters(lock)) { |
| - struct rt_mutex_waiter *next; |
| - |
| - next = rt_mutex_top_waiter(lock); |
| + if (next) |
| plist_add(&next->pi_list_entry, &pendowner->pi_waiters); |
| - } |
| + |
| raw_spin_unlock(&pendowner->pi_lock); |
| } |
| |
| -- |
| 1.7.1.1 |
| |