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/** @file sync.c
*
* @brief locks.
*
* @author Hanjie Wu (hanjiew)
* @bug No functional bugs
*/
#include <x86/asm.h>
#include <interrupt.h>
#include <sched.h>
#include <sync.h>
void mutex_lock(mutex_t* m) {
thread_t* current = get_current();
int old_if = spl_lock(&m->guard);
if (m->locked == 0) {
m->locked = 1;
spl_unlock(&m->guard, old_if);
return;
}
queue_insert_tail(&m->waiters, ¤t->sched_link);
current->status = THREAD_BLOCKED;
int old_if2 = spl_lock(&ready_lock);
thread_t* t = select_next();
spl_unlock(&ready_lock, old_if2);
/* release m->gaurd last, otherwise other thread may switch to us before
* yielding
*/
yield_to_spl_unlock(t, &m->guard, old_if);
}
void mutex_unlock(mutex_t* m) {
int old_if = spl_lock(&m->guard);
if (m->waiters == NULL) {
m->locked = 0;
spl_unlock(&m->guard, old_if);
return;
}
/* transfer lock ownership to t */
thread_t* t =
queue_data(queue_remove_head(&m->waiters), thread_t, sched_link);
int old_if2 = spl_lock(&ready_lock);
insert_ready_head(t);
spl_unlock(&ready_lock, old_if2);
spl_unlock(&m->guard, old_if);
}
void cv_wait(cv_t* cv, mutex_t* m) {
thread_t* current = get_current();
int old_if = spl_lock(&cv->guard);
queue_insert_tail(&cv->waiters, ¤t->sched_link);
current->status = THREAD_BLOCKED;
mutex_unlock(m);
int old_if2 = spl_lock(&ready_lock);
thread_t* t = select_next();
spl_unlock(&ready_lock, old_if2);
yield_to_spl_unlock(t, &cv->guard, old_if);
/* some threads may jump in so a condition check in a while loop is required
* outside
*/
mutex_lock(m);
}
void cv_signal(cv_t* cv) {
int old_if = spl_lock(&cv->guard);
if (cv->waiters == NULL) {
spl_unlock(&cv->guard, old_if);
return;
}
thread_t* t =
queue_data(queue_remove_head(&cv->waiters), thread_t, sched_link);
int old_if2 = spl_lock(&ready_lock);
insert_ready_head(t);
spl_unlock(&ready_lock, old_if2);
spl_unlock(&cv->guard, old_if);
}
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