From afffc6c1805d98e08e778cddb644a666e78cfcfd Mon Sep 17 00:00:00 2001 From: Davidlohr Bueso Date: Sun, 1 Feb 2015 22:16:24 -0800 Subject: [PATCH] locking/rtmutex: Optimize setting task running after being blocked We explicitly mark the task running after returning from a __rt_mutex_slowlock() call, which does the actual sleeping via wait-wake-trylocking. As such, this patch does two things: (1) refactors the code so that setting current to TASK_RUNNING is done by __rt_mutex_slowlock(), and not by the callers. The downside to this is that it becomes a bit unclear when at what point we block. As such I've added a comment that the task blocks when calling __rt_mutex_slowlock() so readers can figure out when it is running again. (2) relaxes setting current's state through __set_current_state(), instead of it's more expensive barrier alternative. There was no need for the implied barrier as we're obviously not planning on blocking. Signed-off-by: Davidlohr Bueso Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Link: http://lkml.kernel.org/r/1422857784.18096.1.camel@stgolabs.net Signed-off-by: Ingo Molnar --- kernel/locking/rtmutex.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c index 7c98873a3077..3059bc2f022d 100644 --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -1130,6 +1130,7 @@ __rt_mutex_slowlock(struct rt_mutex *lock, int state, set_current_state(state); } + __set_current_state(TASK_RUNNING); return ret; } @@ -1188,10 +1189,9 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state, ret = task_blocks_on_rt_mutex(lock, &waiter, current, chwalk); if (likely(!ret)) + /* sleep on the mutex */ ret = __rt_mutex_slowlock(lock, state, timeout, &waiter); - set_current_state(TASK_RUNNING); - if (unlikely(ret)) { remove_waiter(lock, &waiter); rt_mutex_handle_deadlock(ret, chwalk, &waiter); @@ -1626,10 +1626,9 @@ int rt_mutex_finish_proxy_lock(struct rt_mutex *lock, set_current_state(TASK_INTERRUPTIBLE); + /* sleep on the mutex */ ret = __rt_mutex_slowlock(lock, TASK_INTERRUPTIBLE, to, waiter); - set_current_state(TASK_RUNNING); - if (unlikely(ret)) remove_waiter(lock, waiter);