From: Matthias Kruk <m@m10k.eu>
Date: Tue, 29 Oct 2019 05:07:20 +0000 (+0900)
Subject: Minor improvements to the scheduler:
X-Git-Url: https://git.corax.cc/?a=commitdiff_plain;h=6aaf4185fb379da1f92860097567344038174b84;p=corax

Minor improvements to the scheduler:
 - Make _unq() return an error if it didn't succeed
 - Add sched_dequeue() function
 - Modify sched_tick() not to put tasks with TASK_STATE_EXIT back onto the ready queue
 - Add a header with prototypes for the functions implemented in sched.c
---

diff --git a/kernel/core/sched.c b/kernel/core/sched.c
index 10a76e3..c52d415 100644
--- a/kernel/core/sched.c
+++ b/kernel/core/sched.c
@@ -54,8 +54,12 @@ static task_t* _dq(struct task_queue **q)
 	return(ret_val);
 }
 
-static void _unq(struct task_queue **q, task_t *t)
+static int _unq(struct task_queue **q, task_t *t)
 {
+	int ret_val;
+
+	ret_val = -ENOENT;
+
 	while(*q) {
 		if((*q)->data == t) {
 			struct task_queue *freeme;
@@ -64,13 +68,14 @@ static void _unq(struct task_queue **q, task_t *t)
 			*q = freeme->next;
 
 			kfree(freeme);
+			ret_val = 0;
 			break;
 		}
 
 		q = &((*q)->next);
 	}
 
-	return;
+	return(ret_val);
 }
 
 void sched_tick(void)
@@ -79,7 +84,8 @@ void sched_tick(void)
 
 	cur_task = task_get_current();
 
-	if(cur_task) {
+	/* skip all this if the task is exitting */
+	if(cur_task && cur_task->t_state != TASK_STATE_EXIT) {
 		/* check if running task has not used up it's quantum yet */
 		if(cur_task->t_rslice) {
 			cur_task->t_rslice--;
@@ -91,7 +97,7 @@ void sched_tick(void)
 		cur_task->t_state = TASK_STATE_READY;
 
 		/* put the task back on the ready queue */
-	    _nq(&_readyq, cur_task);
+		_nq(&_readyq, cur_task);
 	}
 
 	/* get the next task from the ready queue */
@@ -155,6 +161,28 @@ int sched_enqueue(task_t *t)
 	return(ret_val);
 }
 
+int sched_dequeue(task_t *t)
+{
+	int ret_val;
+
+	ret_val = -EINVAL;
+
+	if(t) {
+		/* remove the task from the ready queue */
+		ret_val = _unq(&_readyq, t);
+
+		/*
+		 * Attempt to remove the task from the wait queue
+		 * if it wasn't on the ready queue.
+		 */
+		if(ret_val < 0) {
+			ret_val = _unq(&_waitq, t);
+		}
+	}
+
+	return(ret_val);
+}
+
 int sched_signal(pid_t pid)
 {
 	task_t *cur_task;
diff --git a/kernel/core/sched.h b/kernel/core/sched.h
new file mode 100644
index 0000000..a37208f
--- /dev/null
+++ b/kernel/core/sched.h
@@ -0,0 +1,12 @@
+#ifndef __CORE_SCHED_H
+#define __CORE_SCHED_H
+
+#include <config.h>
+
+void sched_tick(void);
+void sched_wait(pid_t);
+int  sched_enqueue(task_t*);
+int  sched_dequeue(task_t*);
+int  sched_signal(pid_t);
+
+#endif /* __CORE_SCHED_H */