make hangck work.  (this is debatable, since it may always be an indication
of another, more serious problem.)

Reference: /n/atom/patch/applied/fsiasata
Date: Mon Apr 14 07:13:10 CES 2014
Signed-off-by: quasntro@quanstro.net

--- /sys/src/fs/amd64/iasata.c	Mon Apr 14 07:12:47 2014
+++ /sys/src/fs/amd64/iasata.c	Mon Apr 14 07:12:48 2014
@@ -996,8 +996,10 @@
 {
 	if((d->portm.feat & Datapi) == 0 && d->active &&
 	    d->totick != 0 && (long)(Ticks - d->totick) > 0){
-		print("%s: drive hung; resetting [%ux] ci %ux\n",
-			dnam(d), d->port->task, d->port->ci);
+		print("%s: drive hung; resetting [%ux] ci %ux %ld %ld\n",
+			dnam(d), d->port->task, d->port->ci, Ticks, d->totick);
+		clearci(d->port);
+		wakeup(&d->portm);
 		d->state = Dreset;
 	}
 }
@@ -1146,7 +1148,7 @@
 	int i;
 
 	for(;;){
-		xtsleep(&kprocr, no, 0, Nms);
+		tsleep(&kprocr, no, 0, Nms);
 		for(i = 0; i < niadrive; i++)
 			checkdrive(iadrive[i], i);
 	}
@@ -1268,6 +1270,7 @@
 	xsleep(&d->portm, ahciclear, &as);
 
 	d->active--;
+assert(d->active == 0);
 	ilock(d);
 	flag = d->portm.flag;
 	task = d->port->task;