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>

3 files changed, 18 insertions, 19 deletions

diff --git a/kernel/futex.c b/kernel/futex.c
index 414a30dbc6b6..c3eebcdac206 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 8faf472c430f..4b1015ef0dc7 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 a09c02982391..9e36aeddce18 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"