void
lock_acquire(struct lock *lock)
{
if(!lock_do_i_hold(lock)) {
spinlock_acquire(&lock->spin_lock);
while(spinlock_data_testandset(&lock->lk_busy) != 0) {
wchan_sleep(lock->lk_wchan, &lock->spin_lock);
}
lock->lk_cpu = curcpu;
lock->lk_thread = curthread;
spinlock_release(&lock->spin_lock);
}
}
/*
* Get the lock.
*
* First disable interrupts (otherwise, if we get a timer interrupt we
* might come back to this lock and deadlock), then use a machine-level
* atomic operation to wait for the lock to be free.
*/
void
spinlock_acquire(struct spinlock *lk)
{
struct cpu *mycpu;
splraise(IPL_NONE, IPL_HIGH);
/* this must work before curcpu initialization */
if (CURCPU_EXISTS()) {
mycpu = curcpu->c_self;
if (lk->lk_holder == mycpu) {
panic("Deadlock on spinlock %p\n", lk);
}
}
else {
mycpu = NULL;
}
while (1) {
/*
* Do test-test-and-set, that is, read first before
* doing test-and-set, to reduce bus contention.
*
* Test-and-set is a machine-level atomic operation
* that writes 1 into the lock word and returns the
* previous value. If that value was 0, the lock was
* previously unheld and we now own it. If it was 1,
* we don't.
*/
if (spinlock_data_get(&lk->lk_lock) != 0) {
continue;
}
if (spinlock_data_testandset(&lk->lk_lock) != 0) {
continue;
}
break;
}
lk->lk_holder = mycpu;
}