From a39fdcf3ce137faf900ac69e1ee69f06264eed6a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thomas=20Lov=C3=A9n?= <thomasloven@gmail.com>
Date: Thu, 29 Mar 2018 12:28:10 +0200
Subject: [PATCH] Adding a scheduler function and cleanup

---
 src/kernel/boot/kmain.c     |  5 +--
 src/kernel/include/thread.h |  6 ++--
 src/kernel/proc/thread.c    | 71 +++++++++++++++++--------------------
 3 files changed, 40 insertions(+), 42 deletions(-)

diff --git a/src/kernel/boot/kmain.c b/src/kernel/boot/kmain.c
index 42e2a01..b060e62 100644
--- a/src/kernel/boot/kmain.c
+++ b/src/kernel/boot/kmain.c
@@ -10,7 +10,7 @@
 
 void thread_function()
 {
-  int thread_id = current_thread()->tid;
+  int thread_id = thread()->tid;
 
   while(1)
   {
@@ -40,7 +40,8 @@ void kmain(uint64_t multiboot_magic, void *multiboot_data)
   ready(new_thread(thread_function));
   ready(new_thread(thread_function));
   ready(new_thread(thread_function));
-  yield();
+
+  start_scheduler();
 
   PANIC("Reached end of kernel main function\n");
   for(;;);
diff --git a/src/kernel/include/thread.h b/src/kernel/include/thread.h
index 0bf316c..397019c 100644
--- a/src/kernel/include/thread.h
+++ b/src/kernel/include/thread.h
@@ -5,15 +5,17 @@
 
 struct thread
 {
-  uintptr_t stack_ptr;
   uint64_t tid;
+  void *stack_ptr;
   uint64_t state;
   QUEUE_SPOT(runQ);
+  uint8_t stack[];
 };
 
+struct thread *thread();
 
 struct thread *new_thread(void (*function)(void));
 void yield();
-struct thread *current_thread();
+void start_scheduler();
 
 void switch_stack(void *old_ptr, void *new_ptr);
diff --git a/src/kernel/proc/thread.c b/src/kernel/proc/thread.c
index 21877f9..1e3bd9b 100644
--- a/src/kernel/proc/thread.c
+++ b/src/kernel/proc/thread.c
@@ -2,12 +2,8 @@
 #include <scheduler.h>
 #include <memory.h>
 
-#define TCB_OFFSET (PAGE_SIZE - sizeof(struct thread))
-#define SWTCH_STACK_SIZE (0x8*8)
-
-struct thread_stack
+struct swtch_stack
 {
-  uint8_t stack[TCB_OFFSET-SWTCH_STACK_SIZE];
   uint64_t RBP;
   uint64_t RBX;
   uint64_t R12;
@@ -16,56 +12,55 @@ struct thread_stack
   uint64_t R15;
   uint64_t RBP2;
   uint64_t ret;
-
-  struct thread tcb;
 }__attribute__((packed));
 
-#define thread_stack(th) (struct thread_stack *)((uintptr_t)th - TCB_OFFSET)
-
-struct thread boot_thread;
-struct thread *_current_thread = 0;
+struct thread *sched_th = 0;
+struct thread *_thread = 0;
 
 uint64_t next_tid = 1;
 struct thread *new_thread(void (*function)(void))
 {
-  struct thread_stack *stk = P2V(pmm_alloc());
-  struct thread *th = &stk->tcb;
-
+  struct thread *th = P2V(pmm_calloc());
   th->tid = next_tid++;
+  th->stack_ptr = incptr(th, PAGE_SIZE - sizeof(struct swtch_stack));
 
+  struct swtch_stack *stk = th->stack_ptr;
   stk->RBP = (uint64_t)&stk->RBP2;
   stk->ret = (uint64_t)function;
-  th->stack_ptr = (uint64_t)&stk->RBP;
 
   return th;
 }
 
-struct thread *current_thread()
+struct thread *thread()
 {
-  return _current_thread;
-}
-
-void set_current_thread(struct thread *th)
-{
-  _current_thread = th;
-}
-
-void switch_thread(struct thread *old, struct thread *new)
-{
-  set_current_thread(new);
-  switch_stack(&old->stack_ptr, &new->stack_ptr);
+  return _thread;
 }
 
 void yield()
 {
-  struct thread *old, *new;
-
-  old = current_thread();
-  if(old)
-    ready(old);
-  else
-    old = &boot_thread;
-  while(!(new = scheduler_next()));
-
-  switch_thread(old, new);
+  switch_stack(&_thread->stack_ptr, &sched_th->stack_ptr);
+}
+
+void scheduler()
+{
+  while(1)
+  {
+    struct thread *new = 0;
+    while(!(new = scheduler_next()));
+
+    _thread = new;
+    switch_stack(&sched_th->stack_ptr, &new->stack_ptr);
+
+    ready(_thread);
+    _thread = 0;
+  }
+}
+
+void start_scheduler()
+{
+  sched_th = new_thread(scheduler);
+  sched_th->tid = (uint64_t)-1;
+
+  uint64_t stack;
+  switch_stack(&stack, &sched_th->stack_ptr);
 }