Fixed a number of issues, subtle and otherwise, with PI semaphores.

PI semaphores now use scheduler callbacks to update priority on a down or
up call. Issues with calling down/up and not calling __down_failed or
__up_wakeup for PI semaphores has been noted (since priority-related things
occured in those calls) and up has been fixed (down is in process).
Callbacks are now responsible for the priority checks and
updates, and some subtle cases are handled that were missed before. Still
need to finish handling GSN-EDF implementation issues related to suspensions.

2 files changed, 11 insertions, 13 deletions

diff --git a/include/linux/rt_param.h b/include/linux/rt_param.h
index f2d6de639e..3dffaec9ce 100644
--- a/include/linux/rt_param.h
+++ b/include/linux/rt_param.h
@@ -61,15 +61,13 @@ typedef struct task_rt_param {
         /* did the task just release a _PI_ semaphore?
          */
         unsigned int            released_pi_sem;
-        /* what is the current "inherited" task priority?
-         * this is a pointer to a pointer of a semaphore,
-         * indicating the task that has the highest
-         * priority and thus indicates the priority of a
-         * task holding a _PI_ semaphore. if this
-         * pointer is zero, then don't use it, no _PI_
-         * sem is being held.
+        /* task representing the current "inherited" task
+         * priority, assigned by inherit_priority and
+         * return priority in the scheduler plugins.
+         * could point to self if PI does not result in
+         * an increased task priority.
          */
-        struct task_struct **inh_task;
+        struct task_struct *inh_task;
         
         unsigned int            is_non_preemptable;
         
@@ -168,7 +166,8 @@ struct pi_semaphore {
         atomic_t count;
         int sleepers;
         wait_queue_head_t wait;
-        struct task_struct *sem_hp_task; /* highest-prio task in queue */
+        struct task_struct *hp_sem_task; /* highest-prio holder/waiter */
+        struct task_struct *holder; /* current lock holder */
         int used; /* is the semaphore being used? */
 };
 
diff --git a/include/linux/sched_plugin.h b/include/linux/sched_plugin.h
index ad6cee3b30..512abfd163 100644
--- a/include/linux/sched_plugin.h
+++ b/include/linux/sched_plugin.h
@@ -62,11 +62,10 @@ typedef long (*enter_np_t) (struct task_struct *);
 typedef long (*exit_np_t) (struct task_struct *);
 
 
-typedef long (*inherit_priority_t) (struct task_struct *offspring,
-                                    struct task_struct *deceased);
+typedef long (*inherit_priority_t) (struct pi_semaphore *sem,
+                                    struct task_struct *new_waiter);
 
-typedef long (*return_priority_t) (struct task_struct *offspring,
-                                   struct task_struct *deceased);
+typedef long (*return_priority_t) (struct pi_semaphore *sem);