From a916d9b2feaeb5934e1f8ba30fde74193a60e8d1 Mon Sep 17 00:00:00 2001
From: Glenn Elliott <gelliott@cs.unc.edu>
Date: Tue, 11 Sep 2012 15:25:29 -0400
Subject: Fix hang from bug in edf_common.c

---
 include/litmus/fdso.h | 22 +++++++++++-----------
 litmus/edf_common.c   | 36 +++++++++++++++++++++++++++++++-----
 litmus/fdso.c         | 10 ++++++----
 litmus/preempt.c      |  5 +++--
 4 files changed, 51 insertions(+), 22 deletions(-)

diff --git a/include/litmus/fdso.h b/include/litmus/fdso.h
index 35be59b970ee..1469c0fd0460 100644
--- a/include/litmus/fdso.h
+++ b/include/litmus/fdso.h
@@ -20,20 +20,20 @@ typedef enum  {
 	FMLP_SEM	= 0,
 	SRP_SEM		= 1,
 
-	RSM_MUTEX	= 2,
-	IKGLP_SEM	= 3,
-	KFMLP_SEM	= 4,
+	MPCP_SEM	= 2,
+	MPCP_VS_SEM	= 3,
+	DPCP_SEM	= 4,
 
-	IKGLP_SIMPLE_GPU_AFF_OBS = 5,
-	IKGLP_GPU_AFF_OBS = 6,
-	KFMLP_SIMPLE_GPU_AFF_OBS = 7,
-	KFMLP_GPU_AFF_OBS = 8,
+	PCP_SEM     = 5,
 
-	MPCP_SEM	= 9,
-	MPCP_VS_SEM	= 10,
-	DPCP_SEM	= 11,
+	RSM_MUTEX	= 6,
+	IKGLP_SEM	= 7,
+	KFMLP_SEM	= 8,
 
-	PCP_SEM         = 12,
+	IKGLP_SIMPLE_GPU_AFF_OBS	= 9,
+	IKGLP_GPU_AFF_OBS			= 10,
+	KFMLP_SIMPLE_GPU_AFF_OBS	= 11,
+	KFMLP_GPU_AFF_OBS			= 12,
 
 	MAX_OBJ_TYPE	= 12
 } obj_type_t;
diff --git a/litmus/edf_common.c b/litmus/edf_common.c
index a1cdc10ea6f1..39ce1816ee04 100644
--- a/litmus/edf_common.c
+++ b/litmus/edf_common.c
@@ -185,11 +185,37 @@ int edf_higher_prio(struct task_struct* first, struct task_struct* second)
 					return 1;
 				}
 #endif
-				/* If the PIDs are the same then the task with the
-				 * inherited priority wins.
-				 */
-				if (!second_task->rt_param.inh_task) {
-					return 1;
+				/* Something could be wrong if you get this far. */
+				if (unlikely(first->rt_param.inh_task ==
+										second->rt_param.inh_task)) {
+					/* Both tasks have the same inherited priority.
+					 * Likely in a bug-condition.
+				     */
+					if (likely(first->pid < second->pid)) {
+						return 1;
+					}
+					else if (first->pid == second->pid) {
+						WARN_ON(1);
+					}
+				}
+				else {
+					/* At least one task must inherit */
+					BUG_ON(!first->rt_param.inh_task &&
+						   !second->rt_param.inh_task);
+
+					/* The task with the inherited priority wins. */
+					if (!second->rt_param.inh_task) {
+						TRACE_CUR("unusual comparison: "
+							"first = %s/%d  first_task = %s/%d  "
+							"second = %s/%d  second_task = %s/%d\n",
+							first->comm, first->pid,
+							(first->rt_param.inh_task) ? first->rt_param.inh_task->comm : "(nil)",
+							(first->rt_param.inh_task) ? first->rt_param.inh_task->pid : 0,
+							second->comm, second->pid,
+							(second->rt_param.inh_task) ? second->rt_param.inh_task->comm : "(nil)",
+							(second->rt_param.inh_task) ? second->rt_param.inh_task->pid : 0);
+						return 1;
+					}
 				}
 			}
 		}
diff --git a/litmus/fdso.c b/litmus/fdso.c
index bac6a35fa17d..2411d16ba486 100644
--- a/litmus/fdso.c
+++ b/litmus/fdso.c
@@ -27,6 +27,12 @@ extern struct fdso_ops generic_affinity_ops;
 static const struct fdso_ops* fdso_ops[] = {
 	&generic_lock_ops, /* FMLP_SEM */
 	&generic_lock_ops, /* SRP_SEM */
+
+	&generic_lock_ops, /* MPCP_SEM */
+	&generic_lock_ops, /* MPCP_VS_SEM */
+	&generic_lock_ops, /* DPCP_SEM */
+	&generic_lock_ops, /* PCP_SEM */
+
 	&generic_lock_ops, /* RSM_MUTEX */
 	&generic_lock_ops, /* IKGLP_SEM */
 	&generic_lock_ops, /* KFMLP_SEM */
@@ -36,10 +42,6 @@ static const struct fdso_ops* fdso_ops[] = {
 	&generic_affinity_ops, /* KFMLP_SIMPLE_GPU_AFF_OBS */
 	&generic_affinity_ops, /* KFMLP_GPU_AFF_OBS */
 #endif
-	&generic_lock_ops, /* MPCP_SEM */
-	&generic_lock_ops, /* MPCP_VS_SEM */
-	&generic_lock_ops, /* DPCP_SEM */
-	&generic_lock_ops, /* PCP_SEM */
 };
 
 static int fdso_create(void** obj_ref, obj_type_t type, void* __user config)
diff --git a/litmus/preempt.c b/litmus/preempt.c
index 28368d5bc046..a2cae3648e15 100644
--- a/litmus/preempt.c
+++ b/litmus/preempt.c
@@ -26,10 +26,11 @@ void sched_state_will_schedule(struct task_struct* tsk)
 			set_sched_state(PICKED_WRONG_TASK);
 		else
 			set_sched_state(WILL_SCHEDULE);
-	} else
+	} else {
 		/* Litmus tasks should never be subject to a remote
 		 * set_tsk_need_resched(). */
-		BUG_ON(is_realtime(tsk));
+		//BUG_ON(is_realtime(tsk));
+	}
 
 #ifdef CONFIG_PREEMPT_STATE_TRACE
 	TRACE_TASK(tsk, "set_tsk_need_resched() ret:%p\n",
-- 
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