Re: [patch 2/2] rtmutex: Detect changes in the pi lock chain

[Peter Zijlstra]

hehe, I can almost follow this code :-)

How about something like this on top?

---
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -260,6 +260,11 @@ static void rt_mutex_adjust_prio(struct
  */
 int max_lock_depth = 1024;
 
+static inline struct rt_mutex *task_blocked_on(struct task_struct *p)
+{
+       return p->pi_blocked_on ? p->pi_blocked_on->lock : NULL;
+}
+
 /*
  * Adjust the priority chain. Also used for deadlock detection.
  * Decreases task's usage by one - may thus free the task.
@@ -443,10 +448,7 @@ static int rt_mutex_adjust_prio_chain(st
         * blocked itself. If yes we store a pointer to the lock for
         * the lock chain change detection above.
         */
-       if (task->pi_blocked_on)
-               next_lock = task->pi_blocked_on->lock;
-       else
-               next_lock = NULL;
+       next_lock = task_blocked_on(task);
 
        raw_spin_unlock_irqrestore(&task->pi_lock, flags);
 
@@ -569,7 +571,7 @@ static int task_blocks_on_rt_mutex(struc
 {
        struct task_struct *owner = rt_mutex_owner(lock);
        struct rt_mutex_waiter *top_waiter = waiter;
-       struct rt_mutex *next_lock = NULL;
+       struct rt_mutex *next_lock;
        unsigned long flags;
        int chain_walk, res;
 
@@ -614,8 +616,8 @@ static int task_blocks_on_rt_mutex(struc
        } else if (debug_rt_mutex_detect_deadlock(waiter, detect_deadlock)) {
                chain_walk = 1;
        }
-       if (owner->pi_blocked_on)
-               next_lock = owner->pi_blocked_on->lock;
+
+       next_lock = task_blocked_on(owner);
 
        raw_spin_unlock_irqrestore(&owner->pi_lock, flags);
        if (!chain_walk)
@@ -705,8 +707,7 @@ static void remove_waiter(struct rt_mute
                }
                __rt_mutex_adjust_prio(owner);
 
-               if (owner->pi_blocked_on)
-                       next_lock = owner->pi_blocked_on->lock;
+               next_lock = task_blocked_on(owner);
 
                raw_spin_unlock_irqrestore(&owner->pi_lock, flags);
        }

pgpCWhvdMKb9P.pgp
Description: PGP signature