//                              -*- Mode: CFA -*-
//
// Cforall Version 1.0.0 Copyright (C) 2016 University of Waterloo
//
// The contents of this file are covered under the licence agreement in the
// file "LICENCE" distributed with Cforall.
//
// kernel.c --
//
// Author           : Thierry Delisle
// Created On       : Tue Jan 17 12:27:26 2016
// Last Modified By : Thierry Delisle
// Last Modified On : --
// Update Count     : 0
//

//Header
#include "kernel"

//C Includes
#include <stddef.h>

//CFA Includes
#include "libhdr.h"
#include "threads"

//Private includes
#define __CFA_INVOKE_PRIVATE__
#include "invoke.h"

processor systemProcessorStorage = {};
processor * systemProcessor = &systemProcessorStorage;

void ?{}(processor * this) {
	this->cor = NULL;
	this->thread_index = 0;
	this->thread_count = 10;
	this->terminated = false;

	for(int i = 0; i < 10; i++) {
		this->threads[i] = NULL;
	}

	LIB_DEBUG_PRINTF("Processor : ctor for core %p (core spots %d)\n", this, this->thread_count);
}

void ^?{}(processor * this) {

}

//-----------------------------------------------------------------------------
// Processor coroutine
struct proc_coroutine {
	processor * proc;
	coroutine c;
};

void ?{}(coroutine * this, processor * proc) {
	this{};
}

DECL_COROUTINE(proc_coroutine)

void ?{}(proc_coroutine * this, processor * proc) {
	(&this->c){proc};
	this->proc = proc;
	proc->cor = this;
}

void ^?{}(proc_coroutine * this) {
	^(&this->c){};
}

void CtxInvokeProcessor(processor * proc) {
	proc_coroutine proc_cor_storage = {proc};
	resume( &proc_cor_storage );
}

//-----------------------------------------------------------------------------
// Processor running routines
void main(proc_coroutine * cor);
thread_h * nextThread(processor * this);
void runThread(processor * this, thread_h * dst);
void spin(processor * this, unsigned int * spin_count);

void main(proc_coroutine * cor) {
	processor * this;
	this = cor->proc;

	thread_h * readyThread = NULL;
	for( unsigned int spin_count = 0; ! this->terminated; spin_count++ ) {
		
		readyThread = nextThread(this);

		if(readyThread) {
			runThread(this, readyThread);
			spin_count = 0;
		} else {
			spin(this, &spin_count);
		}		
	}

	LIB_DEBUG_PRINTF("Kernel : core %p terminated\n", this);
}

thread_h * nextThread(processor * this) {
	for(int i = 0; i < this->thread_count; i++) {
		this->thread_index = (this->thread_index + 1) % this->thread_count;	
		
		thread_h * thrd = this->threads[this->thread_index];
		if(thrd) return thrd;
	}

	return NULL;
}

void runThread(processor * this, thread_h * dst) {
	coroutine * proc_ctx = get_coroutine(this->cor);
	coroutine * thrd_ctx = get_coroutine(dst);
	thrd_ctx->last = proc_ctx;

	// context switch to specified coroutine
	// Which is now the current_coroutine
	LIB_DEBUG_PRINTF("Kernel : switching to ctx %p (from %p, current %p)\n", thrd_ctx, proc_ctx, current_coroutine);
	current_coroutine = thrd_ctx;
	CtxSwitch( proc_ctx->stack.context, thrd_ctx->stack.context );
	current_coroutine = proc_ctx;
	LIB_DEBUG_PRINTF("Kernel : returned from ctx %p (to %p, current %p)\n", thrd_ctx, proc_ctx, current_coroutine);

	// when CtxSwitch returns we are back in the processor coroutine
}

void spin(processor * this, unsigned int * spin_count) {
	(*spin_count)++;
}

//-----------------------------------------------------------------------------
// Kernel runner (Temporary)

void scheduler_add( struct thread_h * thrd ) {
	LIB_DEBUG_PRINTF("Kernel : scheduling %p on core %p (%d spots)\n", thrd, systemProcessor, systemProcessor->thread_count);
	for(int i = 0; i < systemProcessor->thread_count; i++) {
		if(systemProcessor->threads[i] == NULL) {
			systemProcessor->threads[i] = thrd;
			return;
		}
	}
	assert(false);
}

void scheduler_remove( struct thread_h * thrd ) {
	LIB_DEBUG_PRINTF("Kernel : unscheduling %p from core %p\n", thrd, systemProcessor);
	for(int i = 0; i < systemProcessor->thread_count; i++) {
		if(systemProcessor->threads[i] == thrd) {
			systemProcessor->threads[i] = NULL;
			break;
		}
	}
	for(int i = 0; i < systemProcessor->thread_count; i++) {
		if(systemProcessor->threads[i] != NULL) {
			return;
		}
	}
	LIB_DEBUG_PRINTF("Kernel : terminating core %p\n\n\n", systemProcessor);	
	systemProcessor->terminated = true;
}

void kernel_run( void ) {
	CtxInvokeProcessor(systemProcessor);
}

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