7 files changed, 54 insertions, 18 deletions

diff --git a/include/litmus/locking.h b/include/litmus/locking.h
index 4d7b870cb443..27eafd002556 100644
--- a/include/litmus/locking.h
+++ b/include/litmus/locking.h
@@ -1,6 +1,8 @@
 #ifndef LITMUS_LOCKING_H
 #define LITMUS_LOCKING_H
 
+#include <linux/list.h>
+
 struct litmus_lock_ops;
 
 /* Generic base struct for LITMUS^RT userspace semaphores.
@@ -9,6 +11,10 @@ struct litmus_lock_ops;
 struct litmus_lock {
         struct litmus_lock_ops *ops;
         int type;
+    
+#ifdef CONFIG_LITMUS_NESTED_LOCKING
+    struct list_head lock_chain;
+#endif
 };
 
 struct litmus_lock_ops {
diff --git a/include/litmus/rt_param.h b/include/litmus/rt_param.h
index d6d799174160..3a054db8ee07 100644
--- a/include/litmus/rt_param.h
+++ b/include/litmus/rt_param.h
@@ -133,7 +133,17 @@ struct rt_param {
          * could point to self if PI does not result in
          * an increased task priority.
          */
-         struct task_struct*    inh_task;
+         struct task_struct*    eff_prio;
+    
+#ifdef CONFIG_LITMUS_NESTED_LOCKING
+    struct task_struct* local_prio;
+    struct task_struct* trans_prio;
+    
+    /* pointer to the last lock acquired */
+    struct litmus_lock* last_lock;
+#endif
+    
+    
 
 #ifdef CONFIG_NP_SECTION
         /* For the FMLP under PSN-EDF, it is required to make the task
diff --git a/litmus/Kconfig b/litmus/Kconfig
index 94b48e199577..841a7e4e9723 100644
--- a/litmus/Kconfig
+++ b/litmus/Kconfig
@@ -60,6 +60,13 @@ config LITMUS_LOCKING
           Say Yes if you want to include locking protocols such as the FMLP and
           Baker's SRP.
 
+config LITMUS_NESTED_LOCKING
+                bool "Support for nested inheritance in locking protocols"
+        depends on LITMUS_LOCKING
+        default n
+        help
+          Enable nested priority inheritance.
+
 endmenu
 
 menu "Performance Enhancements"
diff --git a/litmus/edf_common.c b/litmus/edf_common.c
index 9b44dc2d8d1e..54cfada586be 100644
--- a/litmus/edf_common.c
+++ b/litmus/edf_common.c
@@ -42,10 +42,10 @@ int edf_higher_prio(struct task_struct* first,
         /* Check for inherited priorities. Change task
          * used for comparison in such a case.
          */
-        if (unlikely(first->rt_param.inh_task))
-                first_task = first->rt_param.inh_task;
-        if (unlikely(second->rt_param.inh_task))
-                second_task = second->rt_param.inh_task;
+        if (unlikely(first->rt_param.eff_prio))
+                first_task = first->rt_param.eff_prio;
+        if (unlikely(second->rt_param.eff_prio))
+                second_task = second->rt_param.eff_prio;
 
         /* Check for priority boosting. Tie-break by start of boosting.
          */
@@ -81,7 +81,7 @@ int edf_higher_prio(struct task_struct* first,
                  * priority wins.
                  */
                 (first_task->pid == second_task->pid &&
-                 !second->rt_param.inh_task)));
+                 !second->rt_param.eff_prio)));
 }
 
 int edf_ready_order(struct bheap_node* a, struct bheap_node* b)
diff --git a/litmus/litmus.c b/litmus/litmus.c
index 301390148d02..40340dfa9d67 100644
--- a/litmus/litmus.c
+++ b/litmus/litmus.c
@@ -302,7 +302,12 @@ static void reinit_litmus_state(struct task_struct* p, int restore)
         /* We probably should not be inheriting any task's priority
          * at this point in time.
          */
-        WARN_ON(p->rt_param.inh_task);
+        WARN_ON(p->rt_param.eff_prio);
+    
+#ifdef CONFIG_LITMUS_NESTED_LOCKING
+    WARN_ON(p->rt_param.local_prio);
+    WARN_ON(p->rt_param.trans_prio);
+#endif
 
         /* Cleanup everything else. */
         memset(&p->rt_param, 0, sizeof(p->rt_param));
@@ -468,7 +473,9 @@ void litmus_exec(void)
         struct task_struct* p = current;
 
         if (is_realtime(p)) {
-                WARN_ON(p->rt_param.inh_task);
+                WARN_ON(p->rt_param.eff_prio);
+        WARN_ON(p->rt_param.local_prio);
+        WARN_ON(p->rt_param.trans_prio);
                 if (tsk_rt(p)->ctrl_page) {
                         free_page((unsigned long) tsk_rt(p)->ctrl_page);
                         tsk_rt(p)->ctrl_page = NULL;
diff --git a/litmus/locking.c b/litmus/locking.c
index 0c1aa6aa40b7..5897beb941cf 100644
--- a/litmus/locking.c
+++ b/litmus/locking.c
@@ -34,8 +34,10 @@ static  int create_generic_lock(void** obj_ref, obj_type_t type, void* __user ar
         int err;
 
         err = litmus->allocate_lock(&lock, type, arg);
-        if (err == 0)
+        if (err == 0) {
+        INIT_LIST_HEAD(&lock->lock_chain);
                 *obj_ref = lock;
+    }
         return err;
 }
 
diff --git a/litmus/sched_gsn_edf.c b/litmus/sched_gsn_edf.c
index 6ed504f4750e..677a932e08be 100644
--- a/litmus/sched_gsn_edf.c
+++ b/litmus/sched_gsn_edf.c
@@ -645,7 +645,7 @@ static long gsnedf_admit_task(struct task_struct* tsk)
 #include <litmus/fdso.h>
 
 /* called with IRQs off */
-static void set_priority_inheritance(struct task_struct* t, struct task_struct* prio_inh)
+static void increase_priority_inheritance(struct task_struct* t, struct task_struct* prio_inh)
 {
         int linked_on;
         int check_preempt = 0;
@@ -653,7 +653,7 @@ static void set_priority_inheritance(struct task_struct* t, struct task_struct*
         raw_spin_lock(&gsnedf_lock);
 
         TRACE_TASK(t, "inherits priority from %s/%d\n", prio_inh->comm, prio_inh->pid);
-        tsk_rt(t)->inh_task = prio_inh;
+        tsk_rt(t)->eff_prio = prio_inh;
 
         linked_on  = tsk_rt(t)->linked_on;
 
@@ -712,7 +712,7 @@ static void set_priority_inheritance(struct task_struct* t, struct task_struct*
 }
 
 /* called with IRQs off */
-static void clear_priority_inheritance(struct task_struct* t)
+static void decrease_priority_inheritance(struct task_struct* t, struct task_struct* prio_inh)
 {
         raw_spin_lock(&gsnedf_lock);
 
@@ -720,8 +720,12 @@ static void clear_priority_inheritance(struct task_struct* t)
          * resource. Thus we can make the following assumption.*/
         BUG_ON(tsk_rt(t)->scheduled_on == NO_CPU);
 
-        TRACE_TASK(t, "priority restored\n");
-        tsk_rt(t)->inh_task = NULL;
+    if(prio_inh)
+        TRACE_TASK(t, "inherited priority decreased to %s/%d\n", prio_inh->comm, prio_inh->pid);
+    else
+        TRACE_TASK(t, "base priority restored.\n");
+        
+        tsk_rt(t)->eff_prio = prio_inh;
 
         /* Check if rescheduling is necessary. We can't use heap_decrease()
          * since the priority was effectively lowered. */
@@ -797,7 +801,7 @@ int gsnedf_fmlp_lock(struct litmus_lock* l)
                 if (edf_higher_prio(t, sem->hp_waiter)) {
                         sem->hp_waiter = t;
                         if (edf_higher_prio(t, sem->owner))
-                                set_priority_inheritance(sem->owner, sem->hp_waiter);
+                                increase_priority_inheritance(sem->owner, sem->hp_waiter);
                 }
 
                 TS_LOCK_SUSPEND;
@@ -865,7 +869,7 @@ int gsnedf_fmlp_unlock(struct litmus_lock* l)
                         /* Well, if next is not the highest-priority waiter,
                          * then it ought to inherit the highest-priority
                          * waiter's priority. */
-                        set_priority_inheritance(next, sem->hp_waiter);
+                        increase_priority_inheritance(next, sem->hp_waiter);
                 }
 
                 /* wake up next */
@@ -875,8 +879,8 @@ int gsnedf_fmlp_unlock(struct litmus_lock* l)
                 sem->owner = NULL;
 
         /* we lose the benefit of priority inheritance (if any) */
-        if (tsk_rt(t)->inh_task)
-                clear_priority_inheritance(t);
+        if (tsk_rt(t)->eff_prio)
+                decrease_priority_inheritance(t, NULL);
 
 out:
         spin_unlock_irqrestore(&sem->wait.lock, flags);