From: Alex Shi <alex.shi@linaro.org>
To: peterz@infradead.org, mingo@redhat.com, corbet@lwn.net,
linux-kernel@vger.kernel.org (open list:LOCKING PRIMITIVES)
Cc: linux-kernel@vger.kernel.org, Alex Shi <alex.shi@linaro.org>,
Steven Rostedt <rostedt@goodmis.org>,
Sebastian Siewior <bigeasy@linutronix.de>,
Thomas Gleixner <tglx@linutronix.de>
Subject: [PATCH 2/3] rtmutex: deboost priority conditionally when rt-mutex unlock
Date: Thu, 13 Apr 2017 22:02:53 +0800 [thread overview]
Message-ID: <1492092174-31734-3-git-send-email-alex.shi@linaro.org> (raw)
In-Reply-To: <1492092174-31734-1-git-send-email-alex.shi@linaro.org>
The rt_mutex_fastunlock() will deboost 'current' task when it should be.
but the rt_mutex_slowunlock() function will set the 'deboost' flag
unconditionally. That cause some unnecessary priority adjustment.
'current' release this lock, so 'current' should be a higher prio
task than the next top waiter, unless the current prio was gotten
from this top waiter, iff so, we need to deboost 'current' after
the lock release.
Signed-off-by: Alex Shi <alex.shi@linaro.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
To: linux-kernel@vger.kernel.org
To: Ingo Molnar <mingo@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
---
kernel/locking/rtmutex.c | 19 ++++++++++++++++---
1 file changed, 16 insertions(+), 3 deletions(-)
diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index 6edc32e..05ff685 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -1037,10 +1037,11 @@ static int task_blocks_on_rt_mutex(struct rt_mutex *lock,
*
* Called with lock->wait_lock held and interrupts disabled.
*/
-static void mark_wakeup_next_waiter(struct wake_q_head *wake_q,
+static bool mark_wakeup_next_waiter(struct wake_q_head *wake_q,
struct rt_mutex *lock)
{
struct rt_mutex_waiter *waiter;
+ bool deboost = false;
raw_spin_lock(¤t->pi_lock);
@@ -1055,6 +1056,15 @@ static void mark_wakeup_next_waiter(struct wake_q_head *wake_q,
rt_mutex_dequeue_pi(current, waiter);
/*
+ * 'current' release this lock, so 'current' should be a higher prio
+ * task than the next top waiter, unless the current prio was gotten
+ * from this top waiter, iff so, we need to deboost 'current' after
+ * the lock release.
+ */
+ if (current->prio == waiter->prio)
+ deboost = true;
+
+ /*
* As we are waking up the top waiter, and the waiter stays
* queued on the lock until it gets the lock, this lock
* obviously has waiters. Just set the bit here and this has
@@ -1067,6 +1077,8 @@ static void mark_wakeup_next_waiter(struct wake_q_head *wake_q,
raw_spin_unlock(¤t->pi_lock);
wake_q_add(wake_q, waiter->task);
+
+ return deboost;
}
/*
@@ -1336,6 +1348,7 @@ static bool __sched rt_mutex_slowunlock(struct rt_mutex *lock,
struct wake_q_head *wake_q)
{
unsigned long flags;
+ bool deboost = false;
/* irqsave required to support early boot calls */
raw_spin_lock_irqsave(&lock->wait_lock, flags);
@@ -1389,12 +1402,12 @@ static bool __sched rt_mutex_slowunlock(struct rt_mutex *lock,
*
* Queue the next waiter for wakeup once we release the wait_lock.
*/
- mark_wakeup_next_waiter(wake_q, lock);
+ deboost = mark_wakeup_next_waiter(wake_q, lock);
raw_spin_unlock_irqrestore(&lock->wait_lock, flags);
/* check PI boosting */
- return true;
+ return deboost;
}
/*
--
1.9.1
next prev parent reply other threads:[~2017-04-13 14:04 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-13 14:02 [RFC PATCH 0/3] rtmutex comments update and trival fix Alex Shi
2017-04-13 14:02 ` [PATCH 1/3] rtmutex: comments update Alex Shi
2017-04-13 15:54 ` Steven Rostedt
2017-04-14 8:52 ` Alex Shi
2017-04-14 18:43 ` Steven Rostedt
2017-04-18 8:38 ` Alex Shi
2017-04-13 16:00 ` Steven Rostedt
2017-04-13 14:02 ` Alex Shi [this message]
2017-04-13 14:23 ` [PATCH 2/3] rtmutex: deboost priority conditionally when rt-mutex unlock Sebastian Siewior
2017-04-13 14:39 ` Peter Zijlstra
2017-04-13 16:09 ` Steven Rostedt
2017-04-13 16:21 ` Peter Zijlstra
2017-04-13 16:40 ` Steven Rostedt
2017-04-13 16:51 ` Peter Zijlstra
2017-04-13 14:02 ` [PATCH 3/3] rtmutex: remove unnecessary adjust prio Alex Shi
2017-04-13 16:15 ` Steven Rostedt
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