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#include <thread.h>
#include <malloc.h>
#include <dbglog.h>
#include <idt.h>
#include <gdt.h>
#include <frame.h>
#include <paging.h>
void save_context_and_enter_scheduler(saved_context_t *ctx);
void irq0_save_context_and_enter_scheduler(saved_context_t *ctx);
void resume_context(saved_context_t *ctx);
thread_t *current_thread = 0;
// ====================== //
// THE PROGRAMMABLE TIMER //
// ====================== //
void set_pit_frequency(uint32_t freq) {
uint32_t divisor = 1193180 / freq;
ASSERT(divisor < 65536); // must fit on 16 bits
uint8_t l = (divisor & 0xFF);
uint8_t h = ((divisor >> 8) & 0xFF);
outb(0x43, 0x36);
outb(0x40, l);
outb(0x40, h);
}
// ============================= //
// HELPER : IF FLAG MANIPULATION //
// ============================= //
static inline bool disable_interrupts() {
uint32_t eflags;
asm volatile("pushf; pop %0" : "=r"(eflags));
asm volatile("cli");
return (eflags & EFLAGS_IF) != 0;
}
static inline void resume_interrupts(bool st) {
if (st) asm volatile("sti");
}
// ================== //
// THE TASK SCHEDULER //
// ================== //
static thread_t *queue_first_thread = 0, *queue_last_thread = 0;
void enqueue_thread(thread_t *t, bool just_ran) {
ASSERT(t->state == T_STATE_RUNNING);
if (queue_first_thread == 0) {
queue_first_thread = queue_last_thread = t;
t->next_in_queue = 0;
} else if (just_ran) {
t->next_in_queue = 0;
queue_last_thread->next_in_queue = t;
queue_last_thread = t;
} else {
t->next_in_queue = queue_first_thread;
queue_first_thread = t;
}
}
thread_t* dequeue_thread() {
thread_t *t = queue_first_thread;
if (t == 0) return 0;
queue_first_thread = t->next_in_queue;
if (queue_first_thread == 0) queue_last_thread = 0;
return t;
}
// ================ //
// THE TASKING CODE //
// ================ //
void run_scheduler() {
// At this point, interrupts are disabled
// This function is expected NEVER TO RETURN
if (current_thread != 0 && current_thread->state == T_STATE_RUNNING) {
enqueue_thread(current_thread, true);
}
current_thread = dequeue_thread();
if (current_thread != 0) {
set_kernel_stack(current_thread->stack_region->addr + current_thread->stack_region->size);
resume_context(¤t_thread->ctx);
} else {
// Wait for an IRQ
asm volatile("sti; hlt");
// At this point an IRQ has happenned
// and has been processed. Loop around.
run_scheduler();
ASSERT(false);
}
}
static void run_thread(void (*entry)(void*), void* data) {
ASSERT(current_thread->state == T_STATE_RUNNING);
switch_pagedir(get_kernel_pagedir());
asm volatile("sti");
entry(data);
exit();
}
thread_t *new_thread(entry_t entry, void* data) {
thread_t *t = (thread_t*)malloc(sizeof(thread_t));
if (t == 0) return 0;
void* stack = region_alloc(KPROC_STACK_SIZE, "Stack", 0);
if (stack == 0) {
free(t);
return 0;
}
for (void* i = stack + PAGE_SIZE; i < stack + KPROC_STACK_SIZE; i += PAGE_SIZE) {
uint32_t f = frame_alloc(1);
if (f == 0) {
region_free_unmap_free(stack);
free(t);
return 0;
}
bool map_ok = pd_map_page(i, f, true);
if (!map_ok) {
PANIC("TODO");
}
}
t->stack_region = find_region(stack);
t->ctx.esp = (uint32_t*)(t->stack_region->addr + t->stack_region->size);
*(--t->ctx.esp) = (uint32_t)data; // push second argument : data
*(--t->ctx.esp) = (uint32_t)entry; // push first argument : entry point
*(--t->ctx.esp) = 0; // push invalid return address (the run_thread function never returns)
t->ctx.eip = (void(*)())run_thread;
t->state = T_STATE_PAUSED;
t->current_pd_d = get_kernel_pagedir();
// used by user processes
t->proc = 0;
t->user_ex_handler = 0;
return t;
}
// ========== //
// SETUP CODE //
// ========== //
static void irq0_handler(registers_t *regs) {
if (current_thread != 0)
irq0_save_context_and_enter_scheduler(¤t_thread->ctx);
}
void threading_setup(entry_t cont, void* arg) {
set_pit_frequency(TASK_SWITCH_FREQUENCY);
idt_set_irq_handler(IRQ0, irq0_handler);
thread_t *t = new_thread(cont, arg);
ASSERT(t != 0);
resume_thread(t, false);
run_scheduler(); // never returns
ASSERT(false);
}
// ======================= //
// TASK STATE MANIPULATION //
// ======================= //
void yield() {
if (current_thread == 0) {
// might happen before threading is initialized
// (but should not...)
dbg_printf("Warning: probable deadlock.\n");
} else {
save_context_and_enter_scheduler(¤t_thread->ctx);
}
}
void pause() {
bool st = disable_interrupts();
current_thread->state = T_STATE_PAUSED;
save_context_and_enter_scheduler(¤t_thread->ctx);
resume_interrupts(st);
}
void exit() {
current_thread->state = T_STATE_FINISHED;
// TODO : add job for deleting the thread, or whatever
yield(); // expected never to return!
ASSERT(false);
}
void resume_thread(thread_t *thread, bool run_at_once) {
bool st = disable_interrupts();
if (thread->state == T_STATE_PAUSED) {
thread->state = T_STATE_RUNNING;
enqueue_thread(thread, false);
}
if (run_at_once) yield();
resume_interrupts(st);
}
/* vim: set ts=4 sw=4 tw=0 noet :*/
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