[PATCH -v3 4/8] rtmutex: Clean up

[Peter Zijlstra]

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

--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1394,7 +1394,7 @@ static int wake_futex_pi(u32 __user *uad
 {
        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 *uad
        /*
         * 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;
 }
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -1330,7 +1330,8 @@ static inline int rt_mutex_slowtrylock(s
 
 /*
  * 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(
 
        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 *lo
 }
 
 /*
- * 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 *loc
                                   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(str
         */
        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);
 }
 
 /**
--- a/kernel/locking/rtmutex_common.h
+++ b/kernel/locking/rtmutex_common.h
@@ -122,7 +122,7 @@ extern void rt_mutex_futex_unlock(struct
 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"