eduOS/kernel/tasks.c
2013-11-27 22:49:30 +01:00

378 lines
10 KiB
C

/*
* Copyright (c) 2010, Stefan Lankes, RWTH Aachen University
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this
* software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <eduos/stddef.h>
#include <eduos/stdlib.h>
#include <eduos/stdio.h>
#include <eduos/tasks.h>
#include <eduos/tasks_types.h>
#include <eduos/spinlock.h>
#include <eduos/errno.h>
/** @brief Array of task structures (aka PCB)
*
* A task's id will be its position in this array.
*/
static task_t task_table[MAX_TASKS] = { \
[0] = {0, TASK_IDLE, NULL, NULL, 0, NULL, NULL}, \
[1 ... MAX_TASKS-1] = {0, TASK_INVALID, NULL, NULL, 0, NULL, NULL}};
static spinlock_irqsave_t table_lock = SPINLOCK_IRQSAVE_INIT;
static readyqueues_t readyqueues = {task_table+0, NULL, 0, 0, {[0 ... MAX_PRIO-2] = {NULL, NULL}}, SPINLOCK_IRQSAVE_INIT};
task_t* current_task = task_table+0;
extern const void boot_stack;
/** @brief helper function for the assembly code to determine the current task
* @return Pointer to the task_t structure of current task
*/
task_t* get_current_task(void)
{
return current_task;
}
uint32_t get_highest_priority(void)
{
return msb(readyqueues.prio_bitmap);
}
int multitasking_init(void)
{
if (BUILTIN_EXPECT(task_table[0].status != TASK_IDLE, 0)) {
kputs("Task 0 is not an idle task\n");
return -ENOMEM;
}
task_table[0].prio = IDLE_PRIO;
task_table[0].stack = (void*) &boot_stack;
return 0;
}
void finish_task_switch(void)
{
task_t* old;
uint8_t prio;
spinlock_irqsave_lock(&readyqueues.lock);
if ((old = readyqueues.old_task) != NULL) {
if (old->status == TASK_INVALID) {
old->stack = NULL;
old->last_stack_pointer = NULL;
readyqueues.old_task = NULL;
} else {
prio = old->prio;
if (!readyqueues.queue[prio-1].first) {
old->next = old->prev = NULL;
readyqueues.queue[prio-1].first = readyqueues.queue[prio-1].last = old;
} else {
old->next = NULL;
old->prev = readyqueues.queue[prio-1].last;
readyqueues.queue[prio-1].last->next = old;
readyqueues.queue[prio-1].last = old;
}
readyqueues.old_task = NULL;
readyqueues.prio_bitmap |= (1 << prio);
}
}
spinlock_irqsave_unlock(&readyqueues.lock);
}
/** @brief A procedure to be called by
* procedures which are called by exiting tasks. */
static void NORETURN do_exit(int arg)
{
task_t* curr_task = current_task;
kprintf("Terminate task: %u, return value %d\n", curr_task->id, arg);
curr_task->status = TASK_FINISHED;
reschedule();
// decrease the number of active tasks
spinlock_irqsave_lock(&readyqueues.lock);
readyqueues.nr_tasks--;
spinlock_irqsave_unlock(&readyqueues.lock);
kprintf("Kernel panic: scheduler found no valid task\n");
while(1) {
HALT;
}
}
/** @brief A procedure to be called by kernel tasks */
void NORETURN leave_kernel_task(void) {
int result;
result = 0; //get_return_value();
do_exit(result);
}
/** @brief Aborting a task is like exiting it with result -1 */
void NORETURN abort(void) {
do_exit(-1);
}
/** @brief Create a task with a specific entry point
*
* @param id Pointer to a tid_t struct were the id shall be set
* @param ep Pointer to the function the task shall start with
* @param arg Arguments list
* @param prio Desired priority of the new task
* @param core_id Start the new task on the core with this id
*
* @return
* - 0 on success
* - -ENOMEM (-12) or -EINVAL (-22) on failure
*/
static int create_task(tid_t* id, entry_point_t ep, void* arg, uint8_t prio)
{
int ret = -ENOMEM;
uint32_t i;
if (BUILTIN_EXPECT(!ep, 0))
return -EINVAL;
if (BUILTIN_EXPECT(prio == IDLE_PRIO, 0))
return -EINVAL;
if (BUILTIN_EXPECT(prio > MAX_PRIO, 0))
return -EINVAL;
spinlock_irqsave_lock(&table_lock);
for(i=0; i<MAX_TASKS; i++) {
if (task_table[i].status == TASK_INVALID) {
task_table[i].id = i;
task_table[i].status = TASK_READY;
task_table[i].last_stack_pointer = NULL;
task_table[i].stack = create_stack(i);
task_table[i].prio = prio;
if (id)
*id = i;
ret = create_default_frame(task_table+i, ep, arg);
// add task in the readyqueues
spinlock_irqsave_lock(&readyqueues.lock);
readyqueues.prio_bitmap |= (1 << prio);
readyqueues.nr_tasks++;
if (!readyqueues.queue[prio-1].first) {
task_table[i].next = task_table[i].prev = NULL;
readyqueues.queue[prio-1].first = task_table+i;
readyqueues.queue[prio-1].last = task_table+i;
} else {
task_table[i].prev = readyqueues.queue[prio-1].last;
task_table[i].next = NULL;
readyqueues.queue[prio-1].last->next = task_table+i;
readyqueues.queue[prio-1].last = task_table+i;
}
spinlock_irqsave_unlock(&readyqueues.lock);
break;
}
}
spinlock_irqsave_unlock(&table_lock);
return ret;
}
int create_kernel_task(tid_t* id, entry_point_t ep, void* args, uint8_t prio)
{
if (prio > MAX_PRIO)
prio = NORMAL_PRIO;
return create_task(id, ep, args, prio);
}
/** @brief Wakeup a blocked task
* @param id The task's tid_t structure
* @return
* - 0 on success
* - -EINVAL (-22) on failure
*/
int wakeup_task(tid_t id)
{
task_t* task;
uint32_t prio;
int ret = -EINVAL;
uint8_t flags;
flags = irq_nested_disable();
task = task_table + id;
prio = task->prio;
if (task->status == TASK_BLOCKED) {
task->status = TASK_READY;
ret = 0;
spinlock_irqsave_lock(&readyqueues.lock);
// increase the number of ready tasks
readyqueues.nr_tasks++;
// add task to the runqueue
if (!readyqueues.queue[prio-1].last) {
readyqueues.queue[prio-1].last = readyqueues.queue[prio-1].first = task;
task->next = task->prev = NULL;
readyqueues.prio_bitmap |= (1 << prio);
} else {
task->prev = readyqueues.queue[prio-1].last;
task->next = NULL;
readyqueues.queue[prio-1].last->next = task;
readyqueues.queue[prio-1].last = task;
}
spinlock_irqsave_unlock(&readyqueues.lock);
}
irq_nested_enable(flags);
return ret;
}
/** @brief Block current task
*
* The current task's status will be changed to TASK_BLOCKED
*
* @return
* - 0 on success
* - -EINVAL (-22) on failure
*/
int block_current_task(void)
{
tid_t id;
uint32_t prio;
int ret = -EINVAL;
uint8_t flags;
flags = irq_nested_disable();
id = current_task->id;
prio = current_task->prio;
if (task_table[id].status == TASK_RUNNING) {
task_table[id].status = TASK_BLOCKED;
ret = 0;
spinlock_irqsave_lock(&readyqueues.lock);
// reduce the number of ready tasks
readyqueues.nr_tasks--;
// remove task from queue
if (task_table[id].prev)
task_table[id].prev->next = task_table[id].next;
if (task_table[id].next)
task_table[id].next->prev = task_table[id].prev;
if (readyqueues.queue[prio-1].first == task_table+id)
readyqueues.queue[prio-1].first = task_table[id].next;
if (readyqueues.queue[prio-1].last == task_table+id) {
readyqueues.queue[prio-1].last = task_table[id].prev;
if (!readyqueues.queue[prio-1].last)
readyqueues.queue[prio-1].last = readyqueues.queue[prio-1].first;
}
// No valid task in queue => update prio_bitmap
if (!readyqueues.queue[prio-1].first)
readyqueues.prio_bitmap &= ~(1 << prio);
spinlock_irqsave_unlock(&readyqueues.lock);
}
irq_nested_enable(flags);
return ret;
}
size_t** scheduler(void)
{
task_t* orig_task;
uint32_t prio;
orig_task = current_task;
spinlock_irqsave_lock(&readyqueues.lock);
/* signalizes that this task could be reused */
if (current_task->status == TASK_FINISHED) {
current_task->status = TASK_INVALID;
readyqueues.old_task = current_task;
} else readyqueues.old_task = NULL; // reset old task
prio = msb(readyqueues.prio_bitmap); // determines highest priority
if (prio > MAX_PRIO) {
if ((current_task->status == TASK_RUNNING) || (current_task->status == TASK_IDLE))
goto get_task_out;
current_task = readyqueues.idle;
} else {
// Does the current task have an higher priority? => no task switch
if ((current_task->prio > prio) && (current_task->status == TASK_RUNNING))
goto get_task_out;
if (current_task->status == TASK_RUNNING) {
current_task->status = TASK_READY;
readyqueues.old_task = current_task;
}
current_task = readyqueues.queue[prio-1].first;
if (BUILTIN_EXPECT(current_task->status == TASK_INVALID, 0)) {
kprintf("Upps!!!!!!! Got invalid task %d, orig task %d\n", current_task->id, orig_task->id);
}
current_task->status = TASK_RUNNING;
// remove new task from queue
// by the way, priority 0 is only used by the idle task and doesn't need own queue
readyqueues.queue[prio-1].first = current_task->next;
if (!current_task->next) {
readyqueues.queue[prio-1].last = NULL;
readyqueues.prio_bitmap &= ~(1 << prio);
}
current_task->next = current_task->prev = NULL;
}
get_task_out:
spinlock_irqsave_unlock(&readyqueues.lock);
if (current_task != orig_task) {
//kprintf("schedule from %u to %u with prio %u\n", orig_task->id, current_task->id, (uint32_t)current_task->prio);
return (size_t**) &(orig_task->last_stack_pointer);
}
return NULL;
}
void reschedule(void)
{
size_t** stack;
uint8_t flags;
flags = irq_nested_disable();
if ((stack = scheduler()))
switch_context(stack);
irq_nested_enable(flags);
}