From ba491114bceab1f578cbdf336cb294a108430251 Mon Sep 17 00:00:00 2001
From: Stefan Lankes <lankes@lfbs.rwth-aachen.de>
Date: Tue, 26 Nov 2013 09:17:14 +0100
Subject: [PATCH] add basic functions to block and to unblock a task

---
 include/eduos/tasks.h | 20 +++++++++++
 kernel/tasks.c        | 83 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 103 insertions(+)

diff --git a/include/eduos/tasks.h b/include/eduos/tasks.h
index 05e89e2..11515c1 100644
--- a/include/eduos/tasks.h
+++ b/include/eduos/tasks.h
@@ -74,6 +74,26 @@ int create_kernel_task(tid_t* id, entry_point_t ep, void* args, uint8_t prio);
  */
 void reschedule(void);
 
+/** @brief Wake up a blocked task
+ *
+ * The task's status will be changed to TASK_READY 
+ *
+ * @return
+ * - 0 on success
+ * - -EINVAL (-22) on failure
+ */
+int wakeup_task(tid_t);
+
+/** @brief Block current task
+ *
+ * The current task's status will be changed to TASK_BLOCKED
+ *
+ * @return
+ * - 0 on success
+ * - -EINVAL (-22) on failure
+ */
+int block_current_task(void);
+
 /** @brief This function shall be called by leaving kernel level tasks */
 void NORETURN leave_kernel_task(void);
 
diff --git a/kernel/tasks.c b/kernel/tasks.c
index 220a495..17a6abf 100644
--- a/kernel/tasks.c
+++ b/kernel/tasks.c
@@ -184,6 +184,89 @@ int create_kernel_task(tid_t* id, entry_point_t ep, void* args, uint8_t prio)
 	return create_task(id, ep, args, prio);
 }
 
+/** @brief Wakeup a blocked task
+ * @param id The task's tid_t structure
+ * @return
+ * - 0 on success
+ * - -EINVAL (-22) on failure
+ */
+int wakeup_task(tid_t id)
+{
+	task_t* task;
+	uint32_t prio;
+	int ret = -EINVAL;
+
+	task = task_table + id;
+	prio = task->prio;
+
+	if (task->status == TASK_BLOCKED) {
+		task->status = TASK_READY;
+		ret = 0;
+
+		// increase the number of ready tasks
+		readyqueues.nr_tasks++;
+
+		// add task to the runqueue
+		if (!readyqueues.queue[prio-1].last) {
+			readyqueues.queue[prio-1].last = readyqueues.queue[prio-1].first = task;
+			task->next = task->prev = NULL;
+			readyqueues.prio_bitmap |= (1 << prio);
+		} else {
+			task->prev = readyqueues.queue[prio-1].last;
+			task->next = NULL;
+			readyqueues.queue[prio-1].last->next = task;
+			readyqueues.queue[prio-1].last = task;
+                }
+	}
+
+	return ret;
+}
+
+/** @brief Block current task
+ *
+ * The current task's status will be changed to TASK_BLOCKED
+ *
+ * @return
+ * - 0 on success
+ * - -EINVAL (-22) on failure
+ */
+int block_current_task(void)
+{
+	tid_t id;
+	uint32_t prio;
+	int ret = -EINVAL;
+
+	id = current_task->id;
+	prio = current_task->prio;
+
+	if (task_table[id].status == TASK_RUNNING) {
+		task_table[id].status = TASK_BLOCKED;
+		ret = 0;
+
+		// reduce the number of ready tasks
+		readyqueues.nr_tasks--;
+
+		// remove task from queue
+		if (task_table[id].prev)
+			task_table[id].prev->next = task_table[id].next;
+		if (task_table[id].next)
+			task_table[id].next->prev = task_table[id].prev;
+		if (readyqueues.queue[prio-1].first == task_table+id)
+			readyqueues.queue[prio-1].first = task_table[id].next;
+		if (readyqueues.queue[prio-1].last == task_table+id) {
+			readyqueues.queue[prio-1].last = task_table[id].prev;
+			if (!readyqueues.queue[prio-1].last)
+				readyqueues.queue[prio-1].last = readyqueues.queue[prio-1].first;
+		}
+
+		// No valid task in queue => update prio_bitmap
+		if (!readyqueues.queue[prio-1].first)
+			readyqueues.prio_bitmap &= ~(1 << prio);
+	}
+
+	return ret;
+}
+
 size_t** scheduler(void)
 {
 	task_t* orig_task;