From d3a77d84a8c09c393673ead13cf2e5a52297a4e3 Mon Sep 17 00:00:00 2001 From: Gregory Haskins 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. ] [ Your display is set for the "iso-8859-1" character set. ] [ Some characters may be displayed incorrectly. ] From: Peter W.Morreale 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 Signed-off-by: Gregory Haskins Signed-off-by: Ingo Molnar Signed-off-by: Thomas Gleixner Signed-off-by: Paul Gortmaker --- kernel/rtmutex.c | 14 +++++++++----- 1 files changed, 9 insertions(+), 5 deletions(-) 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); } -- 1.7.0.4