7 files changed, 192 insertions, 108 deletions

diff --git a/include/litmus/aux_tasks.h b/include/litmus/aux_tasks.h
index 3bb6b26fef09..87745c1c0df0 100644..100755
--- a/include/litmus/aux_tasks.h
+++ b/include/litmus/aux_tasks.h
@@ -6,6 +6,8 @@ struct task_struct;
 /* admit an aux task with default parameters */
 //int admit_aux_task(struct task_struct *t);
 
+int make_aux_task_if_required(struct task_struct *t);
+
 /* call on an aux task when it exits real-time */
 int exit_aux_task(struct task_struct *t);
 
diff --git a/include/litmus/litmus.h b/include/litmus/litmus.h
index db2987a24686..711b88e2b3d1 100644..100755
--- a/include/litmus/litmus.h
+++ b/include/litmus/litmus.h
@@ -32,6 +32,7 @@ struct task_struct* __waitqueue_remove_first(wait_queue_head_t *wq);
 #define NO_CPU                  0xffffffff
 
 void litmus_fork(struct task_struct *tsk);
+void litmus_post_fork_thread(struct task_struct *tsk);
 void litmus_exec(void);
 /* clean up real-time state of a task */
 void exit_litmus(struct task_struct *dead_tsk);
diff --git a/include/litmus/rt_param.h b/include/litmus/rt_param.h
index cb7c3ac64339..aca78a835529 100644..100755
--- a/include/litmus/rt_param.h
+++ b/include/litmus/rt_param.h
@@ -41,6 +41,12 @@ typedef enum {
         PRECISE_SIGNALS,        /* budget signals are triggered with hrtimers */
 } budget_signal_policy_t;
 
+typedef enum {
+        AUX_ENABLE      = 0x1,
+        AUX_CURRENT = (AUX_ENABLE<<1),
+        AUX_FUTURE      = (AUX_CURRENT<<2)
+} aux_flags_t;
+
 /* We use the common priority interpretation "lower index == higher priority",
  * which is commonly used in fixed-priority schedulability analysis papers.
  * So, a numerically lower priority value implies higher scheduling priority,
@@ -370,6 +376,7 @@ struct aux_data
         struct list_head        aux_tasks;
         struct binheap          aux_task_owners;
         unsigned int            initialized:1;
+        unsigned int            aux_future:1;
 };
 #endif
 
diff --git a/kernel/fork.c b/kernel/fork.c
index 25c6111fe3a6..7491c4f5e78c 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1370,8 +1370,12 @@ static struct task_struct *copy_process(unsigned long clone_flags,
         write_unlock_irq(&tasklist_lock);
         proc_fork_connector(p);
         cgroup_post_fork(p);
-        if (clone_flags & CLONE_THREAD)
+        if (clone_flags & CLONE_THREAD) {
                 threadgroup_fork_read_unlock(current);
+#ifdef CONFIG_REALTIME_AUX_TASKS
+                litmus_post_fork_thread(p);
+#endif
+        }
         perf_event_fork(p);
         return p;
 
diff --git a/litmus/aux_tasks.c b/litmus/aux_tasks.c
index bd7bcbed58fe..e5f3c82d32e9 100755
--- a/litmus/aux_tasks.c
+++ b/litmus/aux_tasks.c
@@ -25,7 +25,7 @@ static int admit_aux_task(struct task_struct *t)
         struct rt_task tp = {
                 .period = 1000000,   /* 1ms */
                 .relative_deadline = 1000000,
-                .exec_cost = 1000000, /* allow full utilization */
+                .exec_cost = 1000000, /* allow full utilization with buget tracking */
                 .phase = 0,
                 .cpu = task_cpu(leader),  /* take CPU of group leader */
                 .budget_policy = QUANTUM_ENFORCEMENT,
@@ -44,17 +44,15 @@ static int admit_aux_task(struct task_struct *t)
 int exit_aux_task(struct task_struct *t)
 {
         int retval = 0;
-        struct task_struct *leader = t->group_leader;
 
         BUG_ON(!tsk_rt(t)->is_aux_task);
 
-        TRACE_CUR("Aux task %s/%d is exiting from %s/%d.\n", t->comm, t->pid, leader->comm, leader->pid);
+        TRACE_CUR("Aux task %s/%d is exiting from %s/%d.\n", t->comm, t->pid, t->group_leader->comm, t->group_leader->pid);
 
+        tsk_rt(t)->is_aux_task = 0;
+        
 #ifdef CONFIG_REALTIME_AUX_TASK_PRIORITY_INHERITANCE
         list_del(&tsk_rt(t)->aux_task_node);
-
-        tsk_rt(t)->is_aux_task = 0;
-
         if (tsk_rt(t)->inh_task) {
                 litmus->__decrease_prio(t, NULL);
         }
@@ -80,10 +78,14 @@ static int aux_tasks_increase_priority(struct task_struct *leader, struct task_s
                 if (!is_realtime(aux)) {
                         TRACE_CUR("skipping non-real-time aux task %s/%d\n", aux->comm, aux->pid);
                 }
-
-                // aux tasks don't touch rt locks, so no nested call needed.
-                TRACE_CUR("increasing %s/%d.\n", aux->comm, aux->pid);
-                retval = litmus->__increase_prio(aux, hp);
+                else if(tsk_rt(aux)->inh_task == hp) {
+                        TRACE_CUR("skipping real-time aux task %s/%d that already inherits from %s/%d\n", aux->comm, aux->pid, hp->comm, hp->pid);
+                }
+                else {
+                        // aux tasks don't touch rt locks, so no nested call needed.
+                        TRACE_CUR("increasing %s/%d.\n", aux->comm, aux->pid);
+                        retval = litmus->__increase_prio(aux, hp);
+                }
         }
 #endif
 
@@ -208,6 +210,54 @@ out:
         return retval;
 }
 
+int make_aux_task_if_required(struct task_struct *t)
+{
+        struct task_struct *leader;
+        int retval = 0;
+        
+        read_lock_irq(&tasklist_lock);  
+        
+        leader = t->group_leader;
+
+        if(!tsk_aux(leader)->initialized || !tsk_aux(leader)->aux_future) {
+                goto out;
+        }
+        
+        TRACE_CUR("Making %s/%d in %s/%d an aux thread.\n", t->comm, t->pid, leader->comm, leader->pid);
+        
+        INIT_LIST_HEAD(&tsk_rt(t)->aux_task_node);
+        INIT_BINHEAP_NODE(&tsk_rt(t)->aux_task_owner_node);
+        
+        retval = admit_aux_task(t);
+        if (retval == 0) {
+                tsk_rt(t)->is_aux_task = 1;
+                
+#ifdef CONFIG_REALTIME_AUX_TASK_PRIORITY_INHERITANCE    
+                list_add_tail(&tsk_rt(t)->aux_task_node, &tsk_aux(leader)->aux_tasks);
+                
+                if (!binheap_empty(&tsk_aux(leader)->aux_task_owners)) {
+                        struct task_struct *hp =
+                                container_of(binheap_top_entry(&tsk_aux(leader)->aux_task_owners, struct rt_param, aux_task_owner_node),
+                                                         struct task_struct, rt_param);
+                        
+                        TRACE_CUR("hp in group: %s/%d\n", hp->comm, hp->pid);
+                        
+                        retval = litmus->__increase_prio(t, (tsk_rt(hp)->inh_task)? tsk_rt(hp)->inh_task : hp);
+                        
+                        if (retval != 0) {
+                                /* don't know how to recover from bugs with prio inheritance.  better just crash. */
+                                read_unlock_irq(&tasklist_lock);
+                                BUG();
+                        }
+                }
+#endif
+        }
+        
+out:
+        read_unlock_irq(&tasklist_lock);
+
+        return retval;
+}
 
 
 long enable_aux_task_owner(struct task_struct *t)
@@ -313,11 +363,12 @@ static int aux_task_owner_max_priority_order(struct binheap_node *a,
 }
 
 
-static long __do_enable_aux_tasks(void)
+static long __do_enable_aux_tasks(int flags)
 {
         long retval = 0;
         struct task_struct *leader;
         struct task_struct *t;
+        int aux_tasks_added = 0;
 
         leader = current->group_leader;
 
@@ -327,34 +378,52 @@ static long __do_enable_aux_tasks(void)
                 tsk_aux(leader)->initialized = 1;
         }
 
+        if (flags & AUX_FUTURE) {
+                tsk_aux(leader)->aux_future = 1;
+        }
+        
         t = leader;
         do {
-                /* doesn't hurt to initialize them both */
-                INIT_LIST_HEAD(&tsk_rt(t)->aux_task_node);
-                INIT_BINHEAP_NODE(&tsk_rt(t)->aux_task_owner_node);
+                if (!tsk_rt(t)->has_aux_tasks && !tsk_rt(t)->is_aux_task) {
+                        /* This may harmlessly reinit unused nodes. TODO: Don't reinit already init nodes. */
+                        /* doesn't hurt to initialize both nodes */
+                        INIT_LIST_HEAD(&tsk_rt(t)->aux_task_node);
+                        INIT_BINHEAP_NODE(&tsk_rt(t)->aux_task_owner_node);
+                }
 
                 TRACE_CUR("Checking task in %s/%d: %s/%d = (p = %llu):\n",
                                   leader->comm, leader->pid, t->comm, t->pid,
                                   tsk_rt(t)->task_params.period);
-
-                /* inspect heap_node to see if it is an rt task */
+                
+                /* inspect period to see if it is an rt task */
                 if (tsk_rt(t)->task_params.period == 0) {
-                        if (!tsk_rt(t)->is_aux_task) {
-                                TRACE_CUR("AUX task in %s/%d: %s/%d:\n", leader->comm, leader->pid, t->comm, t->pid);
-                                /* hasn't been aux_tasks_increase_priorityted into rt. make it a aux. */
-                                tsk_rt(t)->is_aux_task = 1;
-
+                        if (flags && AUX_CURRENT) {
+                                if (!tsk_rt(t)->is_aux_task) {
+                                        int admit_ret;
+                                        
+                                        TRACE_CUR("AUX task in %s/%d: %s/%d:\n", leader->comm, leader->pid, t->comm, t->pid);
+
+                                        admit_ret = admit_aux_task(t);
+                                        
+                                        if (admit_ret == 0) {
+                                                /* hasn't been aux_tasks_increase_priorityted into rt. make it a aux. */
+                                                tsk_rt(t)->is_aux_task = 1;
+                                                aux_tasks_added = 1;
+                                                
 #ifdef CONFIG_REALTIME_AUX_TASK_PRIORITY_INHERITANCE
-                                list_add_tail(&tsk_rt(t)->aux_task_node, &tsk_aux(leader)->aux_tasks);
+                                                list_add_tail(&tsk_rt(t)->aux_task_node, &tsk_aux(leader)->aux_tasks);
 #endif
-
-                                (void)admit_aux_task(t);
+                                        }
+                                }
+                                else {
+                                        TRACE_CUR("AUX task in %s/%d is already set up: %s/%d\n", leader->comm, leader->pid, t->comm, t->pid);
+                                }
                         }
                         else {
-                                TRACE_CUR("AUX task in %s/%d is already set up: %s/%d\n", leader->comm, leader->pid, t->comm, t->pid);
+                                TRACE_CUR("Not changing thread in %s/%d to AUX task: %s/%d\n", leader->comm, leader->pid, t->comm, t->pid);
                         }
                 }
-                else {
+                else if (!tsk_rt(t)->is_aux_task) {  /* don't let aux tasks get aux tasks of their own */
                         if (!tsk_rt(t)->has_aux_tasks) {
                                 TRACE_CUR("task in %s/%d: %s/%d:\n", leader->comm, leader->pid, t->comm, t->pid);
                                 tsk_rt(t)->has_aux_tasks = 1;
@@ -369,19 +438,18 @@ static long __do_enable_aux_tasks(void)
 
 
 #ifdef CONFIG_REALTIME_AUX_TASK_PRIORITY_INHERITANCE
-        if (!binheap_empty(&tsk_aux(leader)->aux_task_owners)) {
+        if (aux_tasks_added && !binheap_empty(&tsk_aux(leader)->aux_task_owners)) {
                 struct task_struct *hp = container_of(binheap_top_entry(&tsk_aux(leader)->aux_task_owners, struct rt_param, aux_task_owner_node),
                                                                                           struct task_struct, rt_param);
-                TRACE_CUR("found hp in group: %s/%d\n", hp->comm, hp->pid);
-                retval = aux_tasks_increase_priority(leader,
-                                                                                         (tsk_rt(hp)->inh_task)? tsk_rt(hp)->inh_task : hp);
+                TRACE_CUR("hp in group: %s/%d\n", hp->comm, hp->pid);
+                retval = aux_tasks_increase_priority(leader, (tsk_rt(hp)->inh_task)? tsk_rt(hp)->inh_task : hp);
         }
 #endif
 
         return retval;
 }
 
-static long __do_disable_aux_tasks(void)
+static long __do_disable_aux_tasks(int flags)
 {
         long retval = 0;
         struct task_struct *leader;
@@ -389,50 +457,56 @@ static long __do_disable_aux_tasks(void)
 
         leader = current->group_leader;
 
-        t = leader;
-        do {
-                if (tsk_rt(t)->is_aux_task) {
-
-                        TRACE_CUR("%s/%d is an aux task.\n", t->comm, t->pid);
-
-                        if (is_realtime(t)) {
-                                long temp_retval;
-                                struct sched_param param = { .sched_priority = 0};
-
-                                TRACE_CUR("%s/%d is real-time. Changing policy to SCHED_NORMAL.\n", t->comm, t->pid);
-
-                                temp_retval = sched_setscheduler_nocheck(t, SCHED_NORMAL, &param);
-
-                                if (temp_retval != 0) {
-                                        TRACE_CUR("error changing policy of %s/%d to SCHED_NORMAL\n", t->comm, t->pid);
-                                        if (retval == 0) {
-                                                retval = temp_retval;
-                                        }
-                                        else {
-                                                TRACE_CUR("prior error (%d) masks new error (%d)\n", retval, temp_retval);
+        if (flags & AUX_FUTURE) {
+                tsk_aux(leader)->aux_future = 0;
+        }
+        
+        if (flags & AUX_CURRENT) {
+                t = leader;
+                do {
+                        if (tsk_rt(t)->is_aux_task) {
+
+                                TRACE_CUR("%s/%d is an aux task.\n", t->comm, t->pid);
+
+                                if (is_realtime(t)) {
+                                        long temp_retval;
+                                        struct sched_param param = { .sched_priority = 0};
+
+                                        TRACE_CUR("%s/%d is real-time. Changing policy to SCHED_NORMAL.\n", t->comm, t->pid);
+
+                                        temp_retval = sched_setscheduler_nocheck(t, SCHED_NORMAL, &param);
+
+                                        if (temp_retval != 0) {
+                                                TRACE_CUR("error changing policy of %s/%d to SCHED_NORMAL\n", t->comm, t->pid);
+                                                if (retval == 0) {
+                                                        retval = temp_retval;
+                                                }
+                                                else {
+                                                        TRACE_CUR("prior error (%d) masks new error (%d)\n", retval, temp_retval);
+                                                }
                                         }
                                 }
-                        }
 
-                        tsk_rt(t)->is_aux_task = 0;
-                }
-                t = next_thread(t);
-        } while(t != leader);
+                                tsk_rt(t)->is_aux_task = 0;
+                        }
+                        t = next_thread(t);
+                } while(t != leader);
+        }
 
         return retval;
 }
 
-asmlinkage long sys_set_aux_tasks(int enable)
+asmlinkage long sys_set_aux_tasks(int flags)
 {
         long retval;
 
         read_lock_irq(&tasklist_lock);
 
-        if (enable) {
-                retval = __do_enable_aux_tasks();
+        if (flags & AUX_ENABLE) {
+                retval = __do_enable_aux_tasks(flags);
         }
         else {
-                retval = __do_disable_aux_tasks();
+                retval = __do_disable_aux_tasks(flags);
         }
 
         read_unlock_irq(&tasklist_lock);
@@ -442,7 +516,7 @@ asmlinkage long sys_set_aux_tasks(int enable)
 
 #else
 
-asmlinkage long sys_set_aux_tasks(int enable)
+asmlinkage long sys_set_aux_tasks(int flags)
 {
         printk("Unsupported. Recompile with CONFIG_REALTIME_AUX_TASKS.\n");
         return -EINVAL;
diff --git a/litmus/edf_common.c b/litmus/edf_common.c
index 5a3f5b417f73..c279bf12a7f5 100755
--- a/litmus/edf_common.c
+++ b/litmus/edf_common.c
@@ -22,7 +22,7 @@
 #include <litmus/fpmath.h>
 #endif
 
-#if defined(CONFIG_EDF_TIE_BREAK_HASH) || defined(CONFIG_REALTIME_AUX_TASKS)
+#if defined(CONFIG_EDF_TIE_BREAK_HASH)
 #include <linux/hash.h>
 static inline long edf_hash(struct task_struct *t)
 {
@@ -43,23 +43,6 @@ static inline long edf_hash(struct task_struct *t)
 }
 #endif
 
-#ifdef CONFIG_REALTIME_AUX_TASK_PRIORITY_INHERITANCE
-int aux_tie_break(struct task_struct *first, struct task_struct *second)
-{
-        long fhash = edf_hash(first);
-        long shash = edf_hash(second);
-        if (fhash < shash) {
-                TRACE_CUR("%s/%d >> %s/%d --- %d\n", first->comm, first->pid, second->comm, second->pid, 1);
-                return 1;
-        }
-        else if(fhash == shash) {
-                TRACE_CUR("%s/%d >> %s/%d --- %d\n", first->comm, first->pid, second->comm, second->pid, (first->pid < second->pid));
-                return first->pid < second->pid;
-        }
-        return 0;
-}
-#endif
-
 
 /* edf_higher_prio -  returns true if first has a higher EDF priority
  *                    than second. Deadline ties are broken by PID.
@@ -93,44 +76,47 @@ int edf_higher_prio(struct task_struct* first, struct task_struct* second)
 
 #if defined(CONFIG_REALTIME_AUX_TASK_PRIORITY_BOOSTED)
         /* run aux tasks at max priority */
+        /* TODO: Actually use prio-boosting. */
         if (first->rt_param.is_aux_task != second->rt_param.is_aux_task)
         {
                 return (first->rt_param.is_aux_task > second->rt_param.is_aux_task);
         }
         else if(first->rt_param.is_aux_task && second->rt_param.is_aux_task)
         {
+                if(first->group_leader == second->group_leader) {
+                        TRACE_CUR("aux tie break!\n");  // tie-break by BASE priority of the aux tasks
+                        goto aux_tie_break;
+                }
                 first = first->group_leader;
                 second = second->group_leader;
         }
 #elif defined(CONFIG_REALTIME_AUX_TASK_PRIORITY_INHERITANCE)
         {
-        int first_lo_aux, second_lo_aux;
-        int first_hi_aux, second_hi_aux;
-        first_lo_aux = first->rt_param.is_aux_task && !first->rt_param.inh_task;
-        second_lo_aux = second->rt_param.is_aux_task && !second->rt_param.inh_task;
-
-        if (first_lo_aux && !second_lo_aux) {
-                TRACE_CUR("%s/%d >> %s/%d --- 0\n", first->comm, first->pid, second->comm, second->pid);
-                return 0;
-        }
-        else if (second_lo_aux && !first_lo_aux) {
-                TRACE_CUR("%s/%d >> %s/%d --- 1\n", first->comm, first->pid, second->comm, second->pid);
-                return 1;
-        }
-        else if (first_lo_aux && second_lo_aux) {
-                int aux_lo_tie_break = aux_tie_break(first, second);
-                TRACE_CUR("low aux tie break: %s/%d >> %s/%d --- %d\n", first->comm, first->pid, second->comm, second->pid, aux_lo_tie_break);
-                return aux_lo_tie_break;
-        }
-
-        first_hi_aux = first->rt_param.is_aux_task && first->rt_param.inh_task;
-        second_hi_aux = second->rt_param.is_aux_task && second->rt_param.inh_task;
-
-        if (first_hi_aux && second_hi_aux && first->rt_param.inh_task == second->rt_param.inh_task) {
-                int aux_hi_tie_break = aux_tie_break(first, second);
-                TRACE_CUR("hi aux tie break: %s/%d >> %s/%d --- %d\n", first->comm, first->pid, second->comm, second->pid, aux_hi_tie_break);
-                return aux_hi_tie_break;
-        }
+                int first_lo_aux = first->rt_param.is_aux_task && !first->rt_param.inh_task;
+                int second_lo_aux = second->rt_param.is_aux_task && !second->rt_param.inh_task;
+
+                /* prioritize aux tasks without inheritance below real-time tasks */
+                if (first_lo_aux || second_lo_aux) {
+                        // one of these is an aux task without inheritance.
+                        if(first_lo_aux && second_lo_aux) {
+                                TRACE_CUR("aux tie break!\n");  // tie-break by BASE priority of the aux tasks
+                                goto aux_tie_break;
+                        }
+                        else {
+                                // make the aux thread lowest priority real-time task
+                                int temp = (first_lo_aux) ? !is_realtime(second) : !is_realtime(first);
+                                TRACE_CUR("%s/%d >> %s/%d --- %d\n", first->comm, first->pid, second->comm, second->pid, temp);
+                                return temp;
+                        }
+                }
+                
+                if (first->rt_param.is_aux_task && second->rt_param.is_aux_task &&
+                        first->rt_param.inh_task == second->rt_param.inh_task) {  // inh_task is !NULL for both tasks since neither was a lo_aux task
+                        // Both aux tasks inherit from the same task, so tie-break
+                        // by base priority of the aux tasks.
+                        TRACE_CUR("aux tie break!\n");
+                        goto aux_tie_break;
+                }
         }
 #endif
 
@@ -174,6 +160,8 @@ int edf_higher_prio(struct task_struct* first, struct task_struct* second)
 
 #endif
 
+aux_tie_break:
+        
         if (!is_realtime(second_task)) {
                 return 1;
         }
diff --git a/litmus/litmus.c b/litmus/litmus.c
index cfd14852502b..8bc159b2fcce 100644..100755
--- a/litmus/litmus.c
+++ b/litmus/litmus.c
@@ -634,6 +634,14 @@ void litmus_fork(struct task_struct* p)
         p->od_table = NULL;
 }
 
+/* Called right before copy_process() returns a forked thread. */
+void litmus_post_fork_thread(struct task_struct* p)
+{
+#ifdef CONFIG_REALTIME_AUX_TASKS
+        make_aux_task_if_required(p);
+#endif
+}
+
 /* Called upon execve().
  * current is doing the exec.
  * Don't let address space specific stuff leak.