It is redundant to wake the grantee task if it is already running
Credit goes to Peter for the general idea.
Signed-off-by: Gregory Haskins <ghaskins@xxxxxxxxxx>
Signed-off-by: Peter Morreale <pmorreale@xxxxxxxxxx>
---
kernel/rtmutex.c | 23 ++++++++++++++++++-----
1 files changed, 18 insertions(+), 5 deletions(-)
diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c
index 15fc6e6..cb27b08 100644
--- a/kernel/rtmutex.c
+++ b/kernel/rtmutex.c
@@ -511,6 +511,24 @@ static void wakeup_next_waiter(struct rt_mutex *lock, int savestate)
pendowner = waiter->task;
waiter->task = NULL;
+ /*
+ * Do the wakeup before the ownership change to give any spinning
+ * waiter grantees a headstart over the other threads that will
+ * trigger once owner changes.
+ */
+ if (!savestate)
+ wake_up_process(pendowner);
+ else {
+ smp_mb();
+ /*
+ * This may appear to be a race, but the barriers close the
+ * window.
+ */
+ if ((pendowner->state != TASK_RUNNING)
+ && (pendowner->state != TASK_RUNNING_MUTEX))
+ wake_up_process_mutex(pendowner);
+ }
+
rt_mutex_set_owner(lock, pendowner, RT_MUTEX_OWNER_PENDING);
spin_unlock(¤t->pi_lock);
@@ -537,11 +555,6 @@ static void wakeup_next_waiter(struct rt_mutex *lock, int savestate)
plist_add(&next->pi_list_entry, &pendowner->pi_waiters);
}
spin_unlock(&pendowner->pi_lock);
-
- if (savestate)
- wake_up_process_mutex(pendowner);
- else
- wake_up_process(pendowner);
}
/*
-
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