Potential lost wakeup in condition variables

[j-piecuch]

cv_wait and cv_wait_timed are supposed to atomically release a lock and go to sleep:

mimiker/sys/kern/condvar.c

Lines 27 to 34 in 4336f9a

	void cv_wait(condvar_t *cv, cv_lock_t m) {
	WITH_NO_PREEMPTION {
	cv->waiters++;
	mutex_unlock(m);
	sleepq_wait(cv, __caller(0));
	}
	mutex_lock(m, __caller(0));
	}

Preemption is disabled between unlocking and going to sleep, but we might get an interrupt. Some interrupt filter routines call cv_signal (e.g. atkbdc_intr), so there is a potential lost wakeup.
One solution would be to use WITH_INTR_DISABLED instead of WITH_NO_PREEMPTION.