From 2500120f64db83fc682f38a83f7f9e03ed8a5123 Mon Sep 17 00:00:00 2001
From: Jakob Odersky <jodersky@gmail.com>
Date: Mon, 17 Mar 2014 16:50:15 +0100
Subject: add spin-locks

---
 kernel/task/include/task/lock.h    | 11 ++++++-----
 kernel/task/sched.c                | 10 ++++++++++
 kernel/time/mcu/atmega2560/clock.c |  2 +-
 main.c                             | 38 +++++++++++++++++---------------------
 4 files changed, 34 insertions(+), 27 deletions(-)

diff --git a/kernel/task/include/task/lock.h b/kernel/task/include/task/lock.h
index eaa661c..47246b2 100644
--- a/kernel/task/include/task/lock.h
+++ b/kernel/task/include/task/lock.h
@@ -1,20 +1,21 @@
 #ifndef LOCK_H
 #define LOCK_H
 
-#include "task/shed.h"
+#include "task/sched.h"
 
-typedef char spin_lock_t;
+typedef volatile char spin_lock_t;
 
 #define SPIN_LOCK_UNLOCKED 0
+#define SPIN_LOCK_LOCKED 0
 
-static inline void spin_lock(struct spin_lock_t* lock) {
+static inline void spin_lock(spin_lock_t* lock) {
   while(*lock != SPIN_LOCK_UNLOCKED) {yield();};
   cli();
-  *lock = 1;
+  *lock = SPIN_LOCK_LOCKED;
   sei();
 }
 
-static inline void spin_unlock(struct spin_lock_t* lock) {
+static inline void spin_unlock(spin_lock_t* lock) {
   cli();
   *lock = SPIN_LOCK_UNLOCKED;
   sei();
diff --git a/kernel/task/sched.c b/kernel/task/sched.c
index 652d562..ceaf9bb 100644
--- a/kernel/task/sched.c
+++ b/kernel/task/sched.c
@@ -35,7 +35,17 @@ void sched_init() {
   ret();
 }
 
+
+#include <avr/io.h>
+void toggle_led() {
+  DDRB |= (1 << 7);
+  PORTB ^= (1 << 7);
+}
+
+
+
 void schedule() {
+  toggle_led();
   if(!list_empty(&ready)) {
     current = list_entry(ready.next, struct tcb_t, queue);
     list_move_tail(ready.next, &ready);
diff --git a/kernel/time/mcu/atmega2560/clock.c b/kernel/time/mcu/atmega2560/clock.c
index 6821456..95622dc 100644
--- a/kernel/time/mcu/atmega2560/clock.c
+++ b/kernel/time/mcu/atmega2560/clock.c
@@ -16,7 +16,7 @@ void clock_init(int ms, void (*tick)()) {
   unsigned long int fcpu = (unsigned long int) F_CPU;
   unsigned long int hz = 1000l / ((unsigned long int) ms);
 
-  unsigned long int hz_counter = fcpu / (1024 * (hz)) - 1;
+  unsigned long int hz_counter = fcpu / (1024l * (hz)) - 1;
   OCR3A = hz_counter;
   on_tick = tick;
 }
diff --git a/main.c b/main.c
index 79ca41b..526d75f 100644
--- a/main.c
+++ b/main.c
@@ -6,54 +6,50 @@
 #include "task/sched.h"
 #include "bug/panic.h"
 #include "bug/debug.h"
+#include "task/lock.h"
+#include "time/clock.h"
 #include "mcu/task/context.h"
 #include "tshield/tshield.h"
 
 #define WAIT_CYCLES(cycles) for (volatile unsigned long i = 0; i < cycles; ++i) {}
 
-struct list_head frozen = LIST_HEAD_INIT(frozen);
+spin_lock_t on_lock = SPIN_LOCK_UNLOCKED;
+volatile char on = 0;
 
-void freeze() __attribute__ ( ( naked ) );
-void freeze() {
-  context_save();
-  sleep_queue(&frozen);
-  schedule();
-  context_restore();
+void read(char id) {
+  while(1) {
+    spin_lock(&on_lock);
+    debug_led(0,on);
+    spin_unlock(&on_lock);
+  }
 }
 
-void blink( char id) {
+void write( char id) {
   while(1) {
-    debug_led(id - 1,1);
-    WAIT_CYCLES((long) 30000);
-    debug_led(id - 1,0);
-    WAIT_CYCLES((long) 30000);
+    spin_lock(&on_lock);
+    on = !on;
+    WAIT_CYCLES(30000);
+    spin_unlock(&on_lock);
   }
 }
 
 
-DECLARE_TASK(task1, DEFAULT_STACK_SIZE, blink, 1);
-DECLARE_TASK(task2, DEFAULT_STACK_SIZE, blink, 2);
-DECLARE_TASK(task3, DEFAULT_STACK_SIZE, blink, 3);
-DECLARE_TASK(task4, DEFAULT_STACK_SIZE, blink, 4);
+DECLARE_TASK(task1, DEFAULT_STACK_SIZE, read, 1);
+DECLARE_TASK(task2, DEFAULT_STACK_SIZE, write, 2);
 
 
 int main(int argc, char *argv[]) {
   cli();
   tshield_init();
-
   
 
   spawn(&task1);
   spawn(&task2);
-  spawn(&task3);
-  spawn(&task4);
   
   sei();
   clock_init(10, schedule);
   clock_start();
   sched_init();
-
-
   panic(); //should never reach here
   while(1){}
 }
-- 
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