Convert the sio driver to use a spin mutex instead of a s_lock. This is

going to hurt sio(4) performance for the time being.  As we get closer to
release and have more of the kernel unlocked we can come back to doing
arcane optimizations to workaround the limitations of the sio hardware.

2 files changed, 116 insertions, 246 deletions

diff --git a/sys/dev/sio/sio.c b/sys/dev/sio/sio.c
index 4dc22ea..9b9fc97 100644
--- a/sys/dev/sio/sio.c
+++ b/sys/dev/sio/sio.c
@@ -96,12 +96,6 @@
 #endif
 #include <isa/ic/ns16550.h>
 
-/* XXX - this is ok because we only do sio fast interrupts on i386 */
-#ifndef __i386__
-#define disable_intr()
-#define enable_intr()
-#endif
-
 #define	LOTS_OF_EVENTS	64	/* helps separate urgent events from input */
 
 #define	CALLOUT_MASK		0x80
@@ -323,7 +317,9 @@ static	void	sio_pci_kludge_unit __P((device_t dev));
 static	int	sio_pci_probe __P((device_t dev));
 #endif /* NPCI > 0 */
 
-static char driver_name[] = "sio";
+static char	driver_name[] = "sio";
+static struct	mtx sio_lock;
+static int	sio_inited;
 
 /* table and macro for fast conversion from a unit number to its com struct */
 static	devclass_t	sio_devclass;
@@ -761,7 +757,6 @@ sioprobe(dev, xrid)
 	u_int		flags = device_get_flags(dev);
 	int		rid;
 	struct resource *port;
-	int		intrsave;
 
 	rid = xrid;
 	port = bus_alloc_resource(dev, SYS_RES_IOPORT, &rid,
@@ -773,6 +768,9 @@ sioprobe(dev, xrid)
 	com->bst = rman_get_bustag(port);
 	com->bsh = rman_get_bushandle(port);
 
+	if (atomic_cmpset_int(&sio_inited, 0, 1))
+		mtx_init(&sio_lock, "sio", MTX_SPIN);
+
 #if 0
 	/*
 	 * XXX this is broken - when we are first called, there are no
@@ -858,9 +856,7 @@ sioprobe(dev, xrid)
 	 * but mask them in the processor as well in case there are some
 	 * (misconfigured) shared interrupts.
 	 */
-	intrsave = save_intr();
-	disable_intr();
-	COM_LOCK();
+	mtx_enter(&sio_lock, MTX_SPIN);
 /* EXTRA DELAY? */
 
 	/*
@@ -957,8 +953,7 @@ sioprobe(dev, xrid)
 			CLR_FLAG(dev, COM_C_IIR_TXRDYBUG);
 		}
 		sio_setreg(com, com_cfcr, CFCR_8BITS);
-		COM_UNLOCK();
-		restore_intr(intrsave);
+		mtx_exit(&sio_lock, MTX_SPIN);
 		bus_release_resource(dev, SYS_RES_IOPORT, rid, port);
 		return (iobase == siocniobase ? 0 : result);
 	}
@@ -998,8 +993,7 @@ sioprobe(dev, xrid)
 	irqmap[3] = isa_irq_pending();
 	failures[9] = (sio_getreg(com, com_iir) & IIR_IMASK) - IIR_NOPEND;
 
-	COM_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&sio_lock, MTX_SPIN);
 
 	irqs = irqmap[1] & ~irqmap[0];
 	if (bus_get_resource(idev, SYS_RES_IRQ, 0, &xirq, NULL) == 0 &&
@@ -1118,7 +1112,6 @@ sioattach(dev, xrid)
 	int		rid;
 	struct resource *port;
 	int		ret;
-	int		intrstate;
 
 	rid = xrid;
 	port = bus_alloc_resource(dev, SYS_RES_IOPORT, &rid,
@@ -1187,10 +1180,8 @@ sioattach(dev, xrid)
 		com->it_in.c_ispeed = com->it_in.c_ospeed = comdefaultrate;
 	} else
 		com->it_in.c_ispeed = com->it_in.c_ospeed = TTYDEF_SPEED;
-	intrstate = save_intr();
 	if (siosetwater(com, com->it_in.c_ispeed) != 0) {
-		COM_UNLOCK();
-		restore_intr(intrstate);
+		mtx_exit(&sio_lock, MTX_SPIN);
 		/*
 		 * Leave i/o resources allocated if this is a `cn'-level
 		 * console, so that other devices can't snarf them.
@@ -1199,8 +1190,7 @@ sioattach(dev, xrid)
 			bus_release_resource(dev, SYS_RES_IOPORT, rid, port);
 		return (ENOMEM);
 	}
-	COM_UNLOCK();
-	restore_intr(intrstate);
+	mtx_exit(&sio_lock, MTX_SPIN);
 	termioschars(&com->it_in);
 	com->it_out = com->it_in;
 
@@ -1436,8 +1426,6 @@ open_top:
 			goto out;
 		}
 	} else {
-		int	intrsave;
-
 		/*
 		 * The device isn't open, so there are no conflicts.
 		 * Initialize it.  Initialization is done twice in many
@@ -1497,9 +1485,7 @@ open_top:
 			}
 		}
 
-		intrsave = save_intr();
-		disable_intr();
-		COM_LOCK();
+		mtx_enter(&sio_lock, MTX_SPIN);
 		(void) inb(com->line_status_port);
 		(void) inb(com->data_port);
 		com->prev_modem_status = com->last_modem_status
@@ -1511,8 +1497,7 @@ open_top:
 			outb(com->intr_ctl_port, IER_ERXRDY | IER_ETXRDY
 						| IER_ERLS | IER_EMSC);
 		}
-		COM_UNLOCK();
-		restore_intr(intrsave);
+		mtx_exit(&sio_lock, MTX_SPIN);
 		/*
 		 * Handle initial DCD.  Callout devices get a fake initial
 		 * DCD (trapdoor DCD).  If we are callout, then any sleeping
@@ -1734,7 +1719,8 @@ siodtrwakeup(chan)
 }
 
 /*
- * Call this function with COM_LOCK.  It will return with the lock still held.
+ * Call this function with the sio_lock mutex held.  It will return with the
+ * lock still held.
  */
 static void
 sioinput(com)
@@ -1745,7 +1731,6 @@ sioinput(com)
 	u_char		line_status;
 	int		recv_data;
 	struct tty	*tp;
-	int		intrsave;
 
 	buf = com->ibuf;
 	tp = com->tp;
@@ -1768,9 +1753,7 @@ sioinput(com)
 			 * semantics instead of the save-and-disable semantics
 			 * that are used everywhere else.
 			 */
-			intrsave = save_intr();
-			COM_UNLOCK();
-			enable_intr();
+			mtx_exit(&sio_lock, MTX_SPIN);
 			incc = com->iptr - buf;
 			if (tp->t_rawq.c_cc + incc > tp->t_ihiwat
 			    && (com->state & CS_RTS_IFLOW
@@ -1791,8 +1774,7 @@ sioinput(com)
 				tp->t_lflag &= ~FLUSHO;
 				comstart(tp);
 			}
-			restore_intr(intrsave);
-			COM_LOCK();
+			mtx_enter(&sio_lock, MTX_SPIN);
 		} while (buf < com->iptr);
 	} else {
 		do {
@@ -1801,9 +1783,7 @@ sioinput(com)
 			 * semantics instead of the save-and-disable semantics
 			 * that are used everywhere else.
 			 */
-			intrsave = save_intr();
-			COM_UNLOCK();
-			enable_intr();
+			mtx_exit(&sio_lock, MTX_SPIN);
 			line_status = buf[com->ierroff];
 			recv_data = *buf++;
 			if (line_status
@@ -1818,8 +1798,7 @@ sioinput(com)
 					recv_data |= TTY_PE;
 			}
 			(*linesw[tp->t_line].l_rint)(recv_data, tp);
-			restore_intr(intrsave);
-			COM_LOCK();
+			mtx_enter(&sio_lock, MTX_SPIN);
 		} while (buf < com->iptr);
 	}
 	com_events -= (com->iptr - com->ibuf);
@@ -1839,14 +1818,17 @@ void
 siointr(arg)
 	void		*arg;
 {
+	struct com_s	*com;
+
 #ifndef COM_MULTIPORT
-	COM_LOCK();
-	siointr1((struct com_s *) arg);
-	COM_UNLOCK();
+	com = (struct com_s *)arg;
+
+	mtx_enter(&sio_lock, MTX_SPIN);
+	siointr1(com);
+	mtx_exit(&sio_lock, MTX_SPIN);
 #else /* COM_MULTIPORT */
 	bool_t		possibly_more_intrs;
 	int		unit;
-	struct com_s	*com;
 
 	/*
 	 * Loop until there is no activity on any port.  This is necessary
@@ -1855,7 +1837,7 @@ siointr(arg)
 	 * devices, then the edge from one may be lost because another is
 	 * on.
 	 */
-	COM_LOCK();
+	mtx_enter(&sio_lock, MTX_SPIN);
 	do {
 		possibly_more_intrs = FALSE;
 		for (unit = 0; unit < sio_numunits; ++unit) {
@@ -1874,7 +1856,7 @@ siointr(arg)
 			/* XXX COM_UNLOCK(); */
 		}
 	} while (possibly_more_intrs);
-	COM_UNLOCK();
+	mtx_exit(&sio_lock, MTX_SPIN);
 #endif /* COM_MULTIPORT */
 }
 
@@ -2264,7 +2246,6 @@ static void
 siopoll(void *dummy)
 {
 	int		unit;
-	int		intrsave;
 
 	if (com_events == 0)
 		return;
@@ -2283,9 +2264,7 @@ repeat:
 			 * Discard any events related to never-opened or
 			 * going-away devices.
 			 */
-			intrsave = save_intr();
-			disable_intr();
-			COM_LOCK();
+			mtx_enter(&sio_lock, MTX_SPIN);
 			incc = com->iptr - com->ibuf;
 			com->iptr = com->ibuf;
 			if (com->state & CS_CHECKMSR) {
@@ -2293,43 +2272,33 @@ repeat:
 				com->state &= ~CS_CHECKMSR;
 			}
 			com_events -= incc;
-			COM_UNLOCK();
-			restore_intr(intrsave);
+			mtx_exit(&sio_lock, MTX_SPIN);
 			continue;
 		}
 		if (com->iptr != com->ibuf) {
-			intrsave = save_intr();
-			disable_intr();
-			COM_LOCK();
+			mtx_enter(&sio_lock, MTX_SPIN);
 			sioinput(com);
-			COM_UNLOCK();
-			restore_intr(intrsave);
+			mtx_exit(&sio_lock, MTX_SPIN);
 		}
 		if (com->state & CS_CHECKMSR) {
 			u_char	delta_modem_status;
 
-			intrsave = save_intr();
-			disable_intr();
-			COM_LOCK();
+			mtx_enter(&sio_lock, MTX_SPIN);
 			delta_modem_status = com->last_modem_status
 					     ^ com->prev_modem_status;
 			com->prev_modem_status = com->last_modem_status;
 			com_events -= LOTS_OF_EVENTS;
 			com->state &= ~CS_CHECKMSR;
-			COM_UNLOCK();
-			restore_intr(intrsave);
+			mtx_exit(&sio_lock, MTX_SPIN);
 			if (delta_modem_status & MSR_DCD)
 				(*linesw[tp->t_line].l_modem)
 					(tp, com->prev_modem_status & MSR_DCD);
 		}
 		if (com->state & CS_ODONE) {
-			intrsave = save_intr();
-			disable_intr();
-			COM_LOCK();
+			mtx_enter(&sio_lock, MTX_SPIN);
 			com_events -= LOTS_OF_EVENTS;
 			com->state &= ~CS_ODONE;
-			COM_UNLOCK();
-			restore_intr(intrsave);
+			mtx_exit(&sio_lock, MTX_SPIN);
 			if (!(com->state & CS_BUSY)
 			    && !(com->extra_state & CSE_BUSYCHECK)) {
 				timeout(siobusycheck, com, hz / 100);
@@ -2357,7 +2326,6 @@ comparam(tp, t)
 	u_char		dlbl;
 	int		s;
 	int		unit;
-	int		intrsave;
 
 	/* do historical conversions */
 	if (t->c_ispeed == 0)
@@ -2429,7 +2397,6 @@ comparam(tp, t)
 	 * the speed change atomically.  Keeping interrupts disabled is
 	 * especially important while com_data is hidden.
 	 */
-	intrsave = save_intr();
 	(void) siosetwater(com, t->c_ispeed);
 
 	if (divisor != 0) {
@@ -2517,8 +2484,7 @@ comparam(tp, t)
 	if (com->state >= (CS_BUSY | CS_TTGO))
 		siointr1(com);
 
-	COM_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&sio_lock, MTX_SPIN);
 	splx(s);
 	comstart(tp);
 	if (com->ibufold != NULL) {
@@ -2529,8 +2495,8 @@ comparam(tp, t)
 }
 
 /*
- * This function must be called with interrupts enabled and the com_lock
- * unlocked.  It will return with interrupts disabled and the com_lock locked.
+ * This function must be called with the sio_lock mutex released and will
+ * return with it obtained.
  */
 static int
 siosetwater(com, speed)
@@ -2552,8 +2518,7 @@ siosetwater(com, speed)
 	for (ibufsize = 128; ibufsize < cp4ticks;)
 		ibufsize <<= 1;
 	if (ibufsize == com->ibufsize) {
-		disable_intr();
-		COM_LOCK();
+		mtx_enter(&sio_lock, MTX_SPIN);
 		return (0);
 	}
 
@@ -2563,8 +2528,7 @@ siosetwater(com, speed)
 	 */
 	ibuf = malloc(2 * ibufsize, M_DEVBUF, M_NOWAIT);
 	if (ibuf == NULL) {
-		disable_intr();
-		COM_LOCK();
+		mtx_enter(&sio_lock, MTX_SPIN);
 		return (ENOMEM);
 	}
 
@@ -2582,8 +2546,7 @@ siosetwater(com, speed)
 	 * Read current input buffer, if any.  Continue with interrupts
 	 * disabled.
 	 */
-	disable_intr();
-	COM_LOCK();
+	mtx_enter(&sio_lock, MTX_SPIN);
 	if (com->iptr != com->ibuf)
 		sioinput(com);
 
@@ -2612,16 +2575,13 @@ comstart(tp)
 	struct com_s	*com;
 	int		s;
 	int		unit;
-	int		intrsave;
 
 	unit = DEV_TO_UNIT(tp->t_dev);
 	com = com_addr(unit);
 	if (com == NULL)
 		return;
 	s = spltty();
-	intrsave = save_intr();
-	disable_intr();
-	COM_LOCK();
+	mtx_enter(&sio_lock, MTX_SPIN);
 	if (tp->t_state & TS_TTSTOP)
 		com->state &= ~CS_TTGO;
 	else
@@ -2634,8 +2594,7 @@ comstart(tp)
 		    && com->state & CS_RTS_IFLOW)
 			outb(com->modem_ctl_port, com->mcr_image |= MCR_RTS);
 	}
-	COM_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&sio_lock, MTX_SPIN);
 	if (tp->t_state & (TS_TIMEOUT | TS_TTSTOP)) {
 		ttwwakeup(tp);
 		splx(s);
@@ -2651,9 +2610,7 @@ comstart(tp)
 						  sizeof com->obuf1);
 			com->obufs[0].l_next = NULL;
 			com->obufs[0].l_queued = TRUE;
-			intrsave = save_intr();
-			disable_intr();
-			COM_LOCK();
+			mtx_enter(&sio_lock, MTX_SPIN);
 			if (com->state & CS_BUSY) {
 				qp = com->obufq.l_next;
 				while ((next = qp->l_next) != NULL)
@@ -2665,8 +2622,7 @@ comstart(tp)
 				com->obufq.l_next = &com->obufs[0];
 				com->state |= CS_BUSY;
 			}
-			COM_UNLOCK();
-			restore_intr(intrsave);
+			mtx_exit(&sio_lock, MTX_SPIN);
 		}
 		if (tp->t_outq.c_cc != 0 && !com->obufs[1].l_queued) {
 			com->obufs[1].l_tail
@@ -2674,9 +2630,7 @@ comstart(tp)
 						  sizeof com->obuf2);
 			com->obufs[1].l_next = NULL;
 			com->obufs[1].l_queued = TRUE;
-			intrsave = save_intr();
-			disable_intr();
-			COM_LOCK();
+			mtx_enter(&sio_lock, MTX_SPIN);
 			if (com->state & CS_BUSY) {
 				qp = com->obufq.l_next;
 				while ((next = qp->l_next) != NULL)
@@ -2688,18 +2642,14 @@ comstart(tp)
 				com->obufq.l_next = &com->obufs[1];
 				com->state |= CS_BUSY;
 			}
-			COM_UNLOCK();
-			restore_intr(intrsave);
+			mtx_exit(&sio_lock, MTX_SPIN);
 		}
 		tp->t_state |= TS_BUSY;
 	}
-	intrsave = save_intr();
-	disable_intr();
-	COM_LOCK();
+	mtx_enter(&sio_lock, MTX_SPIN);
 	if (com->state >= (CS_BUSY | CS_TTGO))
 		siointr1(com);	/* fake interrupt to start output */
-	COM_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&sio_lock, MTX_SPIN);
 	ttwwakeup(tp);
 	splx(s);
 }
@@ -2710,14 +2660,11 @@ comstop(tp, rw)
 	int		rw;
 {
 	struct com_s	*com;
-	int		intrsave;
 
 	com = com_addr(DEV_TO_UNIT(tp->t_dev));
 	if (com == NULL || com->gone)
 		return;
-	intrsave = save_intr();
-	disable_intr();
-	COM_LOCK();
+	mtx_enter(&sio_lock, MTX_SPIN);
 	if (rw & FWRITE) {
 		if (com->hasfifo)
 #ifdef COM_ESP
@@ -2744,8 +2691,7 @@ comstop(tp, rw)
 		com_events -= (com->iptr - com->ibuf);
 		com->iptr = com->ibuf;
 	}
-	COM_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&sio_lock, MTX_SPIN);
 	comstart(tp);
 }
 
@@ -2757,7 +2703,6 @@ commctl(com, bits, how)
 {
 	int	mcr;
 	int	msr;
-	int	intrsave;
 
 	if (how == DMGET) {
 		bits = TIOCM_LE;	/* XXX - always enabled while open */
@@ -2789,9 +2734,7 @@ commctl(com, bits, how)
 		mcr |= MCR_RTS;
 	if (com->gone)
 		return(0);
-	intrsave = save_intr();
-	disable_intr();
-	COM_LOCK();
+	mtx_enter(&sio_lock, MTX_SPIN);
 	switch (how) {
 	case DMSET:
 		outb(com->modem_ctl_port,
@@ -2804,8 +2747,7 @@ commctl(com, bits, how)
 		outb(com->modem_ctl_port, com->mcr_image &= ~mcr);
 		break;
 	}
-	COM_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&sio_lock, MTX_SPIN);
 	return (0);
 }
 
@@ -2853,7 +2795,6 @@ comwakeup(chan)
 {
 	struct com_s	*com;
 	int		unit;
-	int		intrsave;
 
 	sio_timeout_handle = timeout(comwakeup, (void *)NULL, sio_timeout);
 
@@ -2865,12 +2806,9 @@ comwakeup(chan)
 		com = com_addr(unit);
 		if (com != NULL && !com->gone
 		    && (com->state >= (CS_BUSY | CS_TTGO) || com->poll)) {
-			intrsave = save_intr();
-			disable_intr();
-			COM_LOCK();
+			mtx_enter(&sio_lock, MTX_SPIN);
 			siointr1(com);
-			COM_UNLOCK();
-			restore_intr(intrsave);
+			mtx_exit(&sio_lock, MTX_SPIN);
 		}
 	}
 
@@ -2892,13 +2830,10 @@ comwakeup(chan)
 			u_int	delta;
 			u_long	total;
 
-			intrsave = save_intr();
-			disable_intr();
-			COM_LOCK();
+			mtx_enter(&sio_lock, MTX_SPIN);
 			delta = com->delta_error_counts[errnum];
 			com->delta_error_counts[errnum] = 0;
-			COM_UNLOCK();
-			restore_intr(intrsave);
+			mtx_exit(&sio_lock, MTX_SPIN);
 			if (delta == 0)
 				continue;
 			total = com->error_counts[errnum] += delta;
diff --git a/sys/isa/sio.c b/sys/isa/sio.c
index 4dc22ea..9b9fc97 100644
--- a/sys/isa/sio.c
+++ b/sys/isa/sio.c
@@ -96,12 +96,6 @@
 #endif
 #include <isa/ic/ns16550.h>
 
-/* XXX - this is ok because we only do sio fast interrupts on i386 */
-#ifndef __i386__
-#define disable_intr()
-#define enable_intr()
-#endif
-
 #define	LOTS_OF_EVENTS	64	/* helps separate urgent events from input */
 
 #define	CALLOUT_MASK		0x80
@@ -323,7 +317,9 @@ static	void	sio_pci_kludge_unit __P((device_t dev));
 static	int	sio_pci_probe __P((device_t dev));
 #endif /* NPCI > 0 */
 
-static char driver_name[] = "sio";
+static char	driver_name[] = "sio";
+static struct	mtx sio_lock;
+static int	sio_inited;
 
 /* table and macro for fast conversion from a unit number to its com struct */
 static	devclass_t	sio_devclass;
@@ -761,7 +757,6 @@ sioprobe(dev, xrid)
 	u_int		flags = device_get_flags(dev);
 	int		rid;
 	struct resource *port;
-	int		intrsave;
 
 	rid = xrid;
 	port = bus_alloc_resource(dev, SYS_RES_IOPORT, &rid,
@@ -773,6 +768,9 @@ sioprobe(dev, xrid)
 	com->bst = rman_get_bustag(port);
 	com->bsh = rman_get_bushandle(port);
 
+	if (atomic_cmpset_int(&sio_inited, 0, 1))
+		mtx_init(&sio_lock, "sio", MTX_SPIN);
+
 #if 0
 	/*
 	 * XXX this is broken - when we are first called, there are no
@@ -858,9 +856,7 @@ sioprobe(dev, xrid)
 	 * but mask them in the processor as well in case there are some
 	 * (misconfigured) shared interrupts.
 	 */
-	intrsave = save_intr();
-	disable_intr();
-	COM_LOCK();
+	mtx_enter(&sio_lock, MTX_SPIN);
 /* EXTRA DELAY? */
 
 	/*
@@ -957,8 +953,7 @@ sioprobe(dev, xrid)
 			CLR_FLAG(dev, COM_C_IIR_TXRDYBUG);
 		}
 		sio_setreg(com, com_cfcr, CFCR_8BITS);
-		COM_UNLOCK();
-		restore_intr(intrsave);
+		mtx_exit(&sio_lock, MTX_SPIN);
 		bus_release_resource(dev, SYS_RES_IOPORT, rid, port);
 		return (iobase == siocniobase ? 0 : result);
 	}
@@ -998,8 +993,7 @@ sioprobe(dev, xrid)
 	irqmap[3] = isa_irq_pending();
 	failures[9] = (sio_getreg(com, com_iir) & IIR_IMASK) - IIR_NOPEND;
 
-	COM_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&sio_lock, MTX_SPIN);
 
 	irqs = irqmap[1] & ~irqmap[0];
 	if (bus_get_resource(idev, SYS_RES_IRQ, 0, &xirq, NULL) == 0 &&
@@ -1118,7 +1112,6 @@ sioattach(dev, xrid)
 	int		rid;
 	struct resource *port;
 	int		ret;
-	int		intrstate;
 
 	rid = xrid;
 	port = bus_alloc_resource(dev, SYS_RES_IOPORT, &rid,
@@ -1187,10 +1180,8 @@ sioattach(dev, xrid)
 		com->it_in.c_ispeed = com->it_in.c_ospeed = comdefaultrate;
 	} else
 		com->it_in.c_ispeed = com->it_in.c_ospeed = TTYDEF_SPEED;
-	intrstate = save_intr();
 	if (siosetwater(com, com->it_in.c_ispeed) != 0) {
-		COM_UNLOCK();
-		restore_intr(intrstate);
+		mtx_exit(&sio_lock, MTX_SPIN);
 		/*
 		 * Leave i/o resources allocated if this is a `cn'-level
 		 * console, so that other devices can't snarf them.
@@ -1199,8 +1190,7 @@ sioattach(dev, xrid)
 			bus_release_resource(dev, SYS_RES_IOPORT, rid, port);
 		return (ENOMEM);
 	}
-	COM_UNLOCK();
-	restore_intr(intrstate);
+	mtx_exit(&sio_lock, MTX_SPIN);
 	termioschars(&com->it_in);
 	com->it_out = com->it_in;
 
@@ -1436,8 +1426,6 @@ open_top:
 			goto out;
 		}
 	} else {
-		int	intrsave;
-
 		/*
 		 * The device isn't open, so there are no conflicts.
 		 * Initialize it.  Initialization is done twice in many
@@ -1497,9 +1485,7 @@ open_top:
 			}
 		}
 
-		intrsave = save_intr();
-		disable_intr();
-		COM_LOCK();
+		mtx_enter(&sio_lock, MTX_SPIN);
 		(void) inb(com->line_status_port);
 		(void) inb(com->data_port);
 		com->prev_modem_status = com->last_modem_status
@@ -1511,8 +1497,7 @@ open_top:
 			outb(com->intr_ctl_port, IER_ERXRDY | IER_ETXRDY
 						| IER_ERLS | IER_EMSC);
 		}
-		COM_UNLOCK();
-		restore_intr(intrsave);
+		mtx_exit(&sio_lock, MTX_SPIN);
 		/*
 		 * Handle initial DCD.  Callout devices get a fake initial
 		 * DCD (trapdoor DCD).  If we are callout, then any sleeping
@@ -1734,7 +1719,8 @@ siodtrwakeup(chan)
 }
 
 /*
- * Call this function with COM_LOCK.  It will return with the lock still held.
+ * Call this function with the sio_lock mutex held.  It will return with the
+ * lock still held.
  */
 static void
 sioinput(com)
@@ -1745,7 +1731,6 @@ sioinput(com)
 	u_char		line_status;
 	int		recv_data;
 	struct tty	*tp;
-	int		intrsave;
 
 	buf = com->ibuf;
 	tp = com->tp;
@@ -1768,9 +1753,7 @@ sioinput(com)
 			 * semantics instead of the save-and-disable semantics
 			 * that are used everywhere else.
 			 */
-			intrsave = save_intr();
-			COM_UNLOCK();
-			enable_intr();
+			mtx_exit(&sio_lock, MTX_SPIN);
 			incc = com->iptr - buf;
 			if (tp->t_rawq.c_cc + incc > tp->t_ihiwat
 			    && (com->state & CS_RTS_IFLOW
@@ -1791,8 +1774,7 @@ sioinput(com)
 				tp->t_lflag &= ~FLUSHO;
 				comstart(tp);
 			}
-			restore_intr(intrsave);
-			COM_LOCK();
+			mtx_enter(&sio_lock, MTX_SPIN);
 		} while (buf < com->iptr);
 	} else {
 		do {
@@ -1801,9 +1783,7 @@ sioinput(com)
 			 * semantics instead of the save-and-disable semantics
 			 * that are used everywhere else.
 			 */
-			intrsave = save_intr();
-			COM_UNLOCK();
-			enable_intr();
+			mtx_exit(&sio_lock, MTX_SPIN);
 			line_status = buf[com->ierroff];
 			recv_data = *buf++;
 			if (line_status
@@ -1818,8 +1798,7 @@ sioinput(com)
 					recv_data |= TTY_PE;
 			}
 			(*linesw[tp->t_line].l_rint)(recv_data, tp);
-			restore_intr(intrsave);
-			COM_LOCK();
+			mtx_enter(&sio_lock, MTX_SPIN);
 		} while (buf < com->iptr);
 	}
 	com_events -= (com->iptr - com->ibuf);
@@ -1839,14 +1818,17 @@ void
 siointr(arg)
 	void		*arg;
 {
+	struct com_s	*com;
+
 #ifndef COM_MULTIPORT
-	COM_LOCK();
-	siointr1((struct com_s *) arg);
-	COM_UNLOCK();
+	com = (struct com_s *)arg;
+
+	mtx_enter(&sio_lock, MTX_SPIN);
+	siointr1(com);
+	mtx_exit(&sio_lock, MTX_SPIN);
 #else /* COM_MULTIPORT */
 	bool_t		possibly_more_intrs;
 	int		unit;
-	struct com_s	*com;
 
 	/*
 	 * Loop until there is no activity on any port.  This is necessary
@@ -1855,7 +1837,7 @@ siointr(arg)
 	 * devices, then the edge from one may be lost because another is
 	 * on.
 	 */
-	COM_LOCK();
+	mtx_enter(&sio_lock, MTX_SPIN);
 	do {
 		possibly_more_intrs = FALSE;
 		for (unit = 0; unit < sio_numunits; ++unit) {
@@ -1874,7 +1856,7 @@ siointr(arg)
 			/* XXX COM_UNLOCK(); */
 		}
 	} while (possibly_more_intrs);
-	COM_UNLOCK();
+	mtx_exit(&sio_lock, MTX_SPIN);
 #endif /* COM_MULTIPORT */
 }
 
@@ -2264,7 +2246,6 @@ static void
 siopoll(void *dummy)
 {
 	int		unit;
-	int		intrsave;
 
 	if (com_events == 0)
 		return;
@@ -2283,9 +2264,7 @@ repeat:
 			 * Discard any events related to never-opened or
 			 * going-away devices.
 			 */
-			intrsave = save_intr();
-			disable_intr();
-			COM_LOCK();
+			mtx_enter(&sio_lock, MTX_SPIN);
 			incc = com->iptr - com->ibuf;
 			com->iptr = com->ibuf;
 			if (com->state & CS_CHECKMSR) {
@@ -2293,43 +2272,33 @@ repeat:
 				com->state &= ~CS_CHECKMSR;
 			}
 			com_events -= incc;
-			COM_UNLOCK();
-			restore_intr(intrsave);
+			mtx_exit(&sio_lock, MTX_SPIN);
 			continue;
 		}
 		if (com->iptr != com->ibuf) {
-			intrsave = save_intr();
-			disable_intr();
-			COM_LOCK();
+			mtx_enter(&sio_lock, MTX_SPIN);
 			sioinput(com);
-			COM_UNLOCK();
-			restore_intr(intrsave);
+			mtx_exit(&sio_lock, MTX_SPIN);
 		}
 		if (com->state & CS_CHECKMSR) {
 			u_char	delta_modem_status;
 
-			intrsave = save_intr();
-			disable_intr();
-			COM_LOCK();
+			mtx_enter(&sio_lock, MTX_SPIN);
 			delta_modem_status = com->last_modem_status
 					     ^ com->prev_modem_status;
 			com->prev_modem_status = com->last_modem_status;
 			com_events -= LOTS_OF_EVENTS;
 			com->state &= ~CS_CHECKMSR;
-			COM_UNLOCK();
-			restore_intr(intrsave);
+			mtx_exit(&sio_lock, MTX_SPIN);
 			if (delta_modem_status & MSR_DCD)
 				(*linesw[tp->t_line].l_modem)
 					(tp, com->prev_modem_status & MSR_DCD);
 		}
 		if (com->state & CS_ODONE) {
-			intrsave = save_intr();
-			disable_intr();
-			COM_LOCK();
+			mtx_enter(&sio_lock, MTX_SPIN);
 			com_events -= LOTS_OF_EVENTS;
 			com->state &= ~CS_ODONE;
-			COM_UNLOCK();
-			restore_intr(intrsave);
+			mtx_exit(&sio_lock, MTX_SPIN);
 			if (!(com->state & CS_BUSY)
 			    && !(com->extra_state & CSE_BUSYCHECK)) {
 				timeout(siobusycheck, com, hz / 100);
@@ -2357,7 +2326,6 @@ comparam(tp, t)
 	u_char		dlbl;
 	int		s;
 	int		unit;
-	int		intrsave;
 
 	/* do historical conversions */
 	if (t->c_ispeed == 0)
@@ -2429,7 +2397,6 @@ comparam(tp, t)
 	 * the speed change atomically.  Keeping interrupts disabled is
 	 * especially important while com_data is hidden.
 	 */
-	intrsave = save_intr();
 	(void) siosetwater(com, t->c_ispeed);
 
 	if (divisor != 0) {
@@ -2517,8 +2484,7 @@ comparam(tp, t)
 	if (com->state >= (CS_BUSY | CS_TTGO))
 		siointr1(com);
 
-	COM_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&sio_lock, MTX_SPIN);
 	splx(s);
 	comstart(tp);
 	if (com->ibufold != NULL) {
@@ -2529,8 +2495,8 @@ comparam(tp, t)
 }
 
 /*
- * This function must be called with interrupts enabled and the com_lock
- * unlocked.  It will return with interrupts disabled and the com_lock locked.
+ * This function must be called with the sio_lock mutex released and will
+ * return with it obtained.
  */
 static int
 siosetwater(com, speed)
@@ -2552,8 +2518,7 @@ siosetwater(com, speed)
 	for (ibufsize = 128; ibufsize < cp4ticks;)
 		ibufsize <<= 1;
 	if (ibufsize == com->ibufsize) {
-		disable_intr();
-		COM_LOCK();
+		mtx_enter(&sio_lock, MTX_SPIN);
 		return (0);
 	}
 
@@ -2563,8 +2528,7 @@ siosetwater(com, speed)
 	 */
 	ibuf = malloc(2 * ibufsize, M_DEVBUF, M_NOWAIT);
 	if (ibuf == NULL) {
-		disable_intr();
-		COM_LOCK();
+		mtx_enter(&sio_lock, MTX_SPIN);
 		return (ENOMEM);
 	}
 
@@ -2582,8 +2546,7 @@ siosetwater(com, speed)
 	 * Read current input buffer, if any.  Continue with interrupts
 	 * disabled.
 	 */
-	disable_intr();
-	COM_LOCK();
+	mtx_enter(&sio_lock, MTX_SPIN);
 	if (com->iptr != com->ibuf)
 		sioinput(com);
 
@@ -2612,16 +2575,13 @@ comstart(tp)
 	struct com_s	*com;
 	int		s;
 	int		unit;
-	int		intrsave;
 
 	unit = DEV_TO_UNIT(tp->t_dev);
 	com = com_addr(unit);
 	if (com == NULL)
 		return;
 	s = spltty();
-	intrsave = save_intr();
-	disable_intr();
-	COM_LOCK();
+	mtx_enter(&sio_lock, MTX_SPIN);
 	if (tp->t_state & TS_TTSTOP)
 		com->state &= ~CS_TTGO;
 	else
@@ -2634,8 +2594,7 @@ comstart(tp)
 		    && com->state & CS_RTS_IFLOW)
 			outb(com->modem_ctl_port, com->mcr_image |= MCR_RTS);
 	}
-	COM_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&sio_lock, MTX_SPIN);
 	if (tp->t_state & (TS_TIMEOUT | TS_TTSTOP)) {
 		ttwwakeup(tp);
 		splx(s);
@@ -2651,9 +2610,7 @@ comstart(tp)
 						  sizeof com->obuf1);
 			com->obufs[0].l_next = NULL;
 			com->obufs[0].l_queued = TRUE;
-			intrsave = save_intr();
-			disable_intr();
-			COM_LOCK();
+			mtx_enter(&sio_lock, MTX_SPIN);
 			if (com->state & CS_BUSY) {
 				qp = com->obufq.l_next;
 				while ((next = qp->l_next) != NULL)
@@ -2665,8 +2622,7 @@ comstart(tp)
 				com->obufq.l_next = &com->obufs[0];
 				com->state |= CS_BUSY;
 			}
-			COM_UNLOCK();
-			restore_intr(intrsave);
+			mtx_exit(&sio_lock, MTX_SPIN);
 		}
 		if (tp->t_outq.c_cc != 0 && !com->obufs[1].l_queued) {
 			com->obufs[1].l_tail
@@ -2674,9 +2630,7 @@ comstart(tp)
 						  sizeof com->obuf2);
 			com->obufs[1].l_next = NULL;
 			com->obufs[1].l_queued = TRUE;
-			intrsave = save_intr();
-			disable_intr();
-			COM_LOCK();
+			mtx_enter(&sio_lock, MTX_SPIN);
 			if (com->state & CS_BUSY) {
 				qp = com->obufq.l_next;
 				while ((next = qp->l_next) != NULL)
@@ -2688,18 +2642,14 @@ comstart(tp)
 				com->obufq.l_next = &com->obufs[1];
 				com->state |= CS_BUSY;
 			}
-			COM_UNLOCK();
-			restore_intr(intrsave);
+			mtx_exit(&sio_lock, MTX_SPIN);
 		}
 		tp->t_state |= TS_BUSY;
 	}
-	intrsave = save_intr();
-	disable_intr();
-	COM_LOCK();
+	mtx_enter(&sio_lock, MTX_SPIN);
 	if (com->state >= (CS_BUSY | CS_TTGO))
 		siointr1(com);	/* fake interrupt to start output */
-	COM_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&sio_lock, MTX_SPIN);
 	ttwwakeup(tp);
 	splx(s);
 }
@@ -2710,14 +2660,11 @@ comstop(tp, rw)
 	int		rw;
 {
 	struct com_s	*com;
-	int		intrsave;
 
 	com = com_addr(DEV_TO_UNIT(tp->t_dev));
 	if (com == NULL || com->gone)
 		return;
-	intrsave = save_intr();
-	disable_intr();
-	COM_LOCK();
+	mtx_enter(&sio_lock, MTX_SPIN);
 	if (rw & FWRITE) {
 		if (com->hasfifo)
 #ifdef COM_ESP
@@ -2744,8 +2691,7 @@ comstop(tp, rw)
 		com_events -= (com->iptr - com->ibuf);
 		com->iptr = com->ibuf;
 	}
-	COM_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&sio_lock, MTX_SPIN);
 	comstart(tp);
 }
 
@@ -2757,7 +2703,6 @@ commctl(com, bits, how)
 {
 	int	mcr;
 	int	msr;
-	int	intrsave;
 
 	if (how == DMGET) {
 		bits = TIOCM_LE;	/* XXX - always enabled while open */
@@ -2789,9 +2734,7 @@ commctl(com, bits, how)
 		mcr |= MCR_RTS;
 	if (com->gone)
 		return(0);
-	intrsave = save_intr();
-	disable_intr();
-	COM_LOCK();
+	mtx_enter(&sio_lock, MTX_SPIN);
 	switch (how) {
 	case DMSET:
 		outb(com->modem_ctl_port,
@@ -2804,8 +2747,7 @@ commctl(com, bits, how)
 		outb(com->modem_ctl_port, com->mcr_image &= ~mcr);
 		break;
 	}
-	COM_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&sio_lock, MTX_SPIN);
 	return (0);
 }
 
@@ -2853,7 +2795,6 @@ comwakeup(chan)
 {
 	struct com_s	*com;
 	int		unit;
-	int		intrsave;
 
 	sio_timeout_handle = timeout(comwakeup, (void *)NULL, sio_timeout);
 
@@ -2865,12 +2806,9 @@ comwakeup(chan)
 		com = com_addr(unit);
 		if (com != NULL && !com->gone
 		    && (com->state >= (CS_BUSY | CS_TTGO) || com->poll)) {
-			intrsave = save_intr();
-			disable_intr();
-			COM_LOCK();
+			mtx_enter(&sio_lock, MTX_SPIN);
 			siointr1(com);
-			COM_UNLOCK();
-			restore_intr(intrsave);
+			mtx_exit(&sio_lock, MTX_SPIN);
 		}
 	}
 
@@ -2892,13 +2830,10 @@ comwakeup(chan)
 			u_int	delta;
 			u_long	total;
 
-			intrsave = save_intr();
-			disable_intr();
-			COM_LOCK();
+			mtx_enter(&sio_lock, MTX_SPIN);
 			delta = com->delta_error_counts[errnum];
 			com->delta_error_counts[errnum] = 0;
-			COM_UNLOCK();
-			restore_intr(intrsave);
+			mtx_exit(&sio_lock, MTX_SPIN);
 			if (delta == 0)
 				continue;
 			total = com->error_counts[errnum] += delta;