From 73db7abddad13d41e67f41431c4ad92c4f364d3c Mon Sep 17 00:00:00 2001
From: Alexis211 <alexis211@gmail.com>
Date: Tue, 10 Aug 2010 21:28:57 +0200
Subject: Now using a simple Round Robin scheduler.

---
 src/kernel/Makefile     |  2 +-
 src/kernel/task/sched.c | 24 ++++++++++++++++++++++++
 src/kernel/task/sched.h |  9 +++++++++
 src/kernel/task/task.c  | 30 +++++++++++-------------------
 src/kernel/task/task.h  |  2 +-
 5 files changed, 46 insertions(+), 21 deletions(-)
 create mode 100644 src/kernel/task/sched.c
 create mode 100644 src/kernel/task/sched.h

(limited to 'src')

diff --git a/src/kernel/Makefile b/src/kernel/Makefile
index eb69cfc..e807fc0 100644
--- a/src/kernel/Makefile
+++ b/src/kernel/Makefile
@@ -1,7 +1,7 @@
 Out = kernel.elf
 Obj = core/loader_.o core/kmain.o core/sys.o \
 	  core/monitor.o task/timer.o \
-	  task/idt.o task/idt_.o task/task.o task/task_.o task/syscall.o \
+	  task/idt.o task/idt_.o task/task.o task/task_.o task/syscall.o task/sched.o \
 	  lib/stdlib.o lib/bitset.o lib/mutex.o \
 	  mem/mem.o mem/paging.o mem/gdt.o mem/heap.o mem/seg.o \
 	  ipc/shm.o ipc/object.o ipc/request.o \
diff --git a/src/kernel/task/sched.c b/src/kernel/task/sched.c
new file mode 100644
index 0000000..d2a4c5b
--- /dev/null
+++ b/src/kernel/task/sched.c
@@ -0,0 +1,24 @@
+#include "sched.h"
+#include <core/sys.h>
+#include <mem/mem.h>
+
+static struct thread *queue = 0, *last = 0;
+
+void sched_enqueue(struct thread *t) {
+	t->queue_next = 0;
+	if (queue == 0) {
+		queue = last = t;
+	} else {
+		last->queue_next = t;
+		last = t;
+	}
+}
+
+struct thread *sched_dequeue() {
+	if (queue == 0) return 0;
+	struct thread *it = queue;
+	ASSERT((it->queue_next == 0 && it == last) || it != last);
+	queue = it->queue_next;
+	if (queue == 0) last = 0;
+	return it;
+}
diff --git a/src/kernel/task/sched.h b/src/kernel/task/sched.h
new file mode 100644
index 0000000..1233a44
--- /dev/null
+++ b/src/kernel/task/sched.h
@@ -0,0 +1,9 @@
+#ifndef DEF_SCHED_H
+#define DEF_SCHED_H
+
+#include "task.h"
+
+void sched_enqueue(struct thread *t);
+struct thread *sched_dequeue();
+
+#endif
diff --git a/src/kernel/task/task.c b/src/kernel/task/task.c
index 68cb249..ccc7cc1 100644
--- a/src/kernel/task/task.c
+++ b/src/kernel/task/task.c
@@ -1,4 +1,5 @@
 #include "task.h"
+#include "sched.h"
 #include <core/sys.h>
 #include <core/monitor.h>
 #include <mem/mem.h>
@@ -56,25 +57,9 @@ void tasking_updateKernelPagetable(uint32_t idx, struct page_table *table, uint3
 	}
 }
 
-/*	Looks through the list of threads, finds the next thread to run. */
-static struct thread *thread_next() {
-	if (current_thread == 0 || current_thread == idle_thread) current_thread = threads;
-	struct thread *ret = current_thread;
-	while (1) {
-		ret = ret->next;
-		if (ret == 0) ret = threads;
-		if (ret->state == TS_RUNNING) {
-		   return ret;
-		}
-		if (ret == current_thread) {
-			return idle_thread;
-		}
-	}
-}
-
 /*	Called when a timer IRQ fires. Does a context switch. */
 void tasking_switch() {
-	if (threads == 0) PANIC("No more threads to run !");
+	if (processes == 0) PANIC("No processes are running !");
 	asm volatile("cli");
 
 	uint32_t esp, ebp, eip;
@@ -91,9 +76,12 @@ void tasking_switch() {
 		current_thread->esp = esp;
 		current_thread->ebp = ebp;
 		current_thread->eip = eip;
+		if (current_thread->state == TS_RUNNING && current_thread != idle_thread) sched_enqueue(current_thread);
 	}
 
-	current_thread = thread_next();
+	current_thread = sched_dequeue();
+	if (current_thread == 0) current_thread = idle_thread;
+
 	pagedir_switch(current_thread->process->pagedir);
 
 	gdt_setKernelStack(((uint32_t)current_thread->kernelStack_addr) + current_thread->kernelStack_size);
@@ -147,7 +135,10 @@ void thread_goInactive() {
 
 /*	Wakes up the given thread. */
 void thread_wakeUp(struct thread* t) {
-	if (t->state == TS_WAKEWAIT) t->state = TS_RUNNING;
+	if (t->state == TS_WAKEWAIT) {
+		t->state = TS_RUNNING;
+		sched_enqueue(t);
+	}
 }
 
 /*	Returns the privilege level of the current process. */
@@ -278,6 +269,7 @@ struct thread *thread_new(struct process *proc, thread_entry entry_point, void *
 	t->eip = (uint32_t)thread_run;
 
 	t->state = TS_RUNNING;
+	sched_enqueue(t);
 
 	if (threads == 0) {
 		threads = t;
diff --git a/src/kernel/task/task.h b/src/kernel/task/task.h
index 3b7d9af..a664258 100644
--- a/src/kernel/task/task.h
+++ b/src/kernel/task/task.h
@@ -45,7 +45,7 @@ struct thread {
 	uint32_t kernelStack_size;
 	struct segment_map *userStack_seg;
 
-	struct thread *next;	//Forms a linked list
+	struct thread *next, *queue_next;	//queue_next is used in sched.c
 };
 
 extern struct thread *current_thread;
-- 
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