semaphores

src/include/kernel/semaphore.h

@@ -0,0 +1,83 @@
+#ifndef _SEMAPHORE_H_INCLUDE
+#define _SEMAPHORE_H_INCLUDE
+
+#include <kernel/sched.h>
+#include <kernel/alloc.h>
+#include <arch/spinlock.h>
+#include <stdbool.h>
+#include <stddef.h>
+
+typedef struct{
+	thread_t** waitingthreads;
+	int lock, count, threadcount;
+} semaphore_t;
+
+
+// a thread count of 0 will be a blockless semaphore
+
+static semaphore_t* sem_init(size_t count, size_t threadptrcount){
+	
+	semaphore_t* semaphore = alloc(sizeof(semaphore_t));
+	if(!semaphore) return NULL;
+	
+	if(threadptrcount){
+		semaphore->waitingthreads = alloc(sizeof(thread_t*) * threadptrcount);
+		semaphore->threadcount = threadptrcount;
+	}
+
+	semaphore->count = count;
+
+	return semaphore;
+}
+
+static bool sem_tryacquire(semaphore_t* sem){
+	
+	spinlock_acquire(&sem->lock);
+
+	bool res = (sem->count > 0);
+
+	if(res)
+		--sem->count;
+	
+
+	spinlock_release(&sem->lock);
+
+	return res;
+
+}
+
+static void sem_wait(semaphore_t* sem){
+	
+	
+	spinlock_acquire(&sem->lock);
+	
+	--sem->count;
+
+	if(sem->count < 0 && sem->threadcount > 0){
+		// TODO block
+	}
+	else if(sem->threadcount == 0){
+		_panic("sem_wait with threadcount 0", 0);
+	}
+	
+	spinlock_release(&sem->lock);
+	
+}
+
+
+static void sem_signal(semaphore_t* sem){
+	
+	
+	spinlock_acquire(&sem->lock);
+	
+	++sem->count;
+
+	if(sem->count <= 0 && sem->threadcount > 0){
+		//TODO run a thread
+	}
+	
+	spinlock_release(&sem->lock);
+	
+}
+
+#endif