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Subject[tip:locking/core] rtmutex: Clean up
Commit-ID:  aa2bfe55366552cb7e93e8709d66e698d79ccc47
Gitweb: http://git.kernel.org/tip/aa2bfe55366552cb7e93e8709d66e698d79ccc47
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Thu, 23 Mar 2017 15:56:10 +0100
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Tue, 4 Apr 2017 11:44:05 +0200

rtmutex: Clean up

Previous patches changed the meaning of the return value of
rt_mutex_slowunlock(); update comments and code to reflect this.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: juri.lelli@arm.com
Cc: bigeasy@linutronix.de
Cc: xlpang@redhat.com
Cc: rostedt@goodmis.org
Cc: mathieu.desnoyers@efficios.com
Cc: jdesfossez@efficios.com
Cc: bristot@redhat.com
Link: http://lkml.kernel.org/r/20170323150216.255058238@infradead.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
kernel/futex.c | 7 ++++---
kernel/locking/rtmutex.c | 28 +++++++++++++---------------
kernel/locking/rtmutex_common.h | 2 +-
3 files changed, 18 insertions(+), 19 deletions(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index 414a30d..c3eebcd 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1394,7 +1394,7 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_pi_state *pi_
{
u32 uninitialized_var(curval), newval;
struct task_struct *new_owner;
- bool deboost = false;
+ bool postunlock = false;
DEFINE_WAKE_Q(wake_q);
int ret = 0;

@@ -1455,12 +1455,13 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_pi_state *pi_
/*
* We've updated the uservalue, this unlock cannot fail.
*/
- deboost = __rt_mutex_futex_unlock(&pi_state->pi_mutex, &wake_q);
+ postunlock = __rt_mutex_futex_unlock(&pi_state->pi_mutex, &wake_q);

out_unlock:
raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);

- rt_mutex_postunlock(&wake_q, deboost);
+ if (postunlock)
+ rt_mutex_postunlock(&wake_q);

return ret;
}
diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index 8faf472..4b1015e 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -1330,7 +1330,8 @@ static inline int rt_mutex_slowtrylock(struct rt_mutex *lock)

/*
* Slow path to release a rt-mutex.
- * Return whether the current task needs to undo a potential priority boosting.
+ *
+ * Return whether the current task needs to call rt_mutex_postunlock().
*/
static bool __sched rt_mutex_slowunlock(struct rt_mutex *lock,
struct wake_q_head *wake_q)
@@ -1401,8 +1402,7 @@ static bool __sched rt_mutex_slowunlock(struct rt_mutex *lock,

raw_spin_unlock_irqrestore(&lock->wait_lock, flags);

- /* check PI boosting */
- return true;
+ return true; /* call rt_mutex_postunlock() */
}

/*
@@ -1449,15 +1449,14 @@ rt_mutex_fasttrylock(struct rt_mutex *lock,
}

/*
- * Undo pi boosting (if necessary) and wake top waiter.
+ * Performs the wakeup of the the top-waiter and re-enables preemption.
*/
-void rt_mutex_postunlock(struct wake_q_head *wake_q, bool deboost)
+void rt_mutex_postunlock(struct wake_q_head *wake_q)
{
wake_up_q(wake_q);

/* Pairs with preempt_disable() in rt_mutex_slowunlock() */
- if (deboost)
- preempt_enable();
+ preempt_enable();
}

static inline void
@@ -1466,14 +1465,12 @@ rt_mutex_fastunlock(struct rt_mutex *lock,
struct wake_q_head *wqh))
{
DEFINE_WAKE_Q(wake_q);
- bool deboost;

if (likely(rt_mutex_cmpxchg_release(lock, current, NULL)))
return;

- deboost = slowfn(lock, &wake_q);
-
- rt_mutex_postunlock(&wake_q, deboost);
+ if (slowfn(lock, &wake_q))
+ rt_mutex_postunlock(&wake_q);
}

/**
@@ -1593,19 +1590,20 @@ bool __sched __rt_mutex_futex_unlock(struct rt_mutex *lock,
*/
preempt_disable();

- return true; /* deboost and wakeups */
+ return true; /* call postunlock() */
}

void __sched rt_mutex_futex_unlock(struct rt_mutex *lock)
{
DEFINE_WAKE_Q(wake_q);
- bool deboost;
+ bool postunlock;

raw_spin_lock_irq(&lock->wait_lock);
- deboost = __rt_mutex_futex_unlock(lock, &wake_q);
+ postunlock = __rt_mutex_futex_unlock(lock, &wake_q);
raw_spin_unlock_irq(&lock->wait_lock);

- rt_mutex_postunlock(&wake_q, deboost);
+ if (postunlock)
+ rt_mutex_postunlock(&wake_q);
}

/**
diff --git a/kernel/locking/rtmutex_common.h b/kernel/locking/rtmutex_common.h
index a09c029..9e36aed 100644
--- a/kernel/locking/rtmutex_common.h
+++ b/kernel/locking/rtmutex_common.h
@@ -122,7 +122,7 @@ extern void rt_mutex_futex_unlock(struct rt_mutex *lock);
extern bool __rt_mutex_futex_unlock(struct rt_mutex *lock,
struct wake_q_head *wqh);

-extern void rt_mutex_postunlock(struct wake_q_head *wake_q, bool deboost);
+extern void rt_mutex_postunlock(struct wake_q_head *wake_q);

#ifdef CONFIG_DEBUG_RT_MUTEXES
# include "rtmutex-debug.h"
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