Messages in this thread Patch in this message | | | From | Gregory Haskins <> | Subject | [PATCH [RT] 06/14] optimize rt lock wakeup | Date | Thu, 21 Feb 2008 10:26:56 -0500 |
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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@novell.com> Signed-off-by: Peter Morreale <pmorreale@novell.com> ---
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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