diff --git a/sys/pc98/cbus/sio.c b/sys/pc98/cbus/sio.c
index 9fef976e4074..2d26234fe706 100644
--- a/sys/pc98/cbus/sio.c
+++ b/sys/pc98/cbus/sio.c
@@ -31,7 +31,7 @@
  * SUCH DAMAGE.
  *
  *	from: @(#)com.c	7.5 (Berkeley) 5/16/91
- *	$Id: sio.c,v 1.31 1997/07/21 13:11:12 kato Exp $
+ *	$Id: sio.c,v 1.32 1997/08/06 09:42:57 kato Exp $
  */
 
 #include "opt_comconsole.h"
@@ -160,6 +160,15 @@
 #include <pccard/slot.h>
 #endif
 
+#ifdef SMP
+#include <machine/smp.h>
+#define COM_LOCK() 	s_lock(&com_lock)
+#define COM_UNLOCK() 	s_unlock(&com_lock)
+#else
+#define COM_LOCK()
+#define COM_UNLOCK()
+#endif /* SMP */
+
 #ifdef APIC_IO
 /*
  * INTs are masked in the (global) IO APIC,
@@ -791,9 +800,11 @@ static int
 card_intr(struct pccard_dev *dp)
 {
 	struct com_s	*com;
+	COM_LOCK();
 	com = com_addr(dp->isahd.id_unit);
 	if (com && !com_addr(dp->isahd.id_unit)->gone)
 		siointr1(com_addr(dp->isahd.id_unit));
+	COM_UNLOCK();
 	return(1);
 }
 #endif /* NCRD > 0 */
@@ -1549,6 +1560,7 @@ open_top:
 		}
 
 		disable_intr();
+		COM_LOCK();
 #ifdef PC98
 		if(IS_8251(com->pc98_if_type)){
 			com_tiocm_bis(com, TIOCM_LE);
@@ -1566,6 +1578,7 @@ open_top:
 #ifdef PC98
 		}
 #endif
+		COM_UNLOCK();
 		enable_intr();
 		/*
 		 * Handle initial DCD.  Callout devices get a fake initial
@@ -1845,7 +1858,9 @@ siointr(unit)
 	int	unit;
 {
 #ifndef COM_MULTIPORT
+	COM_LOCK();
 	siointr1(com_addr(unit));
+	COM_UNLOCK();
 #else /* COM_MULTIPORT */
 	struct com_s    *com;
 	bool_t		possibly_more_intrs;
@@ -1857,6 +1872,7 @@ siointr(unit)
 	 * devices, then the edge from one may be lost because another is
 	 * on.
 	 */
+	COM_LOCK();
 	do {
 		possibly_more_intrs = FALSE;
 		for (unit = 0; unit < NSIO; ++unit) {
@@ -1877,6 +1893,7 @@ siointr(unit)
 			}
 		}
 	} while (possibly_more_intrs);
+	COM_UNLOCK();
 #endif /* COM_MULTIPORT */
 }
 
@@ -2383,6 +2400,7 @@ repeat:
 			 * loop.
 			 */
 			disable_intr();
+			COM_LOCK();
 			incc = com->iptr - com->ibuf;
 			com->iptr = com->ibuf;
 			if (com->state & CS_CHECKMSR) {
@@ -2390,6 +2408,7 @@ repeat:
 				com->state &= ~CS_CHECKMSR;
 			}
 			com_events -= incc;
+			COM_UNLOCK();
 			enable_intr();
 			if (incc != 0)
 				log(LOG_DEBUG,
@@ -2405,6 +2424,7 @@ repeat:
 		} else {
 			buf = ibuf;
 			disable_intr();
+			COM_LOCK();
 			incc = com->iptr - buf;
 			com_events -= incc;
 			if (ibuf == com->ibuf1)
@@ -2440,6 +2460,7 @@ repeat:
 #endif
 				outb(com->modem_ctl_port,
 				     com->mcr_image |= MCR_RTS);
+			COM_UNLOCK();
 			enable_intr();
 			com->ibuf = ibuf;
 		}
@@ -2451,11 +2472,13 @@ repeat:
 			if(!IS_8251(com->pc98_if_type)){
 #endif
 			disable_intr();
+			COM_LOCK();
 			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();
 			enable_intr();
 			if (delta_modem_status & MSR_DCD)
 				(*linesw[tp->t_line].l_modem)
@@ -2466,8 +2489,10 @@ repeat:
 		}
 		if (com->state & CS_ODONE) {
 			disable_intr();
+			COM_LOCK();
 			com_events -= LOTS_OF_EVENTS;
 			com->state &= ~CS_ODONE;
+			COM_UNLOCK();
 			enable_intr();
 			if (!(com->state & CS_BUSY)
 			    && !(com->extra_state & CSE_BUSYCHECK)) {
@@ -2655,9 +2680,11 @@ comparam(tp, t)
 	}
 #endif
 	disable_intr();
+	COM_LOCK();
 retry:
 	com->state &= ~CS_TTGO;
 	txtimeout = tp->t_timeout;
+	COM_UNLOCK();
 	enable_intr();
 #ifdef PC98
 	if(IS_8251(com->pc98_if_type)){
@@ -2685,7 +2712,9 @@ retry:
 		if (error != 0 && error != EAGAIN) {
 			if (!(tp->t_state & TS_TTSTOP)) {
 				disable_intr();
+				COM_LOCK();
 				com->state |= CS_TTGO;
+				COM_UNLOCK();
 				enable_intr();
 			}
 			splx(s);
@@ -2694,6 +2723,7 @@ retry:
 	}
 
 	disable_intr();		/* very important while com_data is hidden */
+	COM_LOCK();
 
 	/*
 	 * XXX - clearing CS_TTGO is not sufficient to stop further output,
@@ -2814,6 +2844,7 @@ retry:
 	if (com->state >= (CS_BUSY | CS_TTGO))
 		siointr1(com);
 
+	COM_UNLOCK();
 	enable_intr();
 	splx(s);
 	comstart(tp);
@@ -2835,6 +2866,7 @@ comstart(tp)
 	com = com_addr(unit);
 	s = spltty();
 	disable_intr();
+	COM_LOCK();
 	if (tp->t_state & TS_TTSTOP)
 		com->state &= ~CS_TTGO;
 	else
@@ -2874,6 +2906,7 @@ comstart(tp)
 #endif
 			outb(com->modem_ctl_port, com->mcr_image |= MCR_RTS);
 	}
+	COM_UNLOCK();
 	enable_intr();
 	if (tp->t_state & (TS_TIMEOUT | TS_TTSTOP)) {
 #ifdef PC98
@@ -2894,6 +2927,7 @@ comstart(tp)
 			com->obufs[0].l_next = NULL;
 			com->obufs[0].l_queued = TRUE;
 			disable_intr();
+			COM_LOCK();
 			if (com->state & CS_BUSY) {
 				qp = com->obufq.l_next;
 				while ((next = qp->l_next) != NULL)
@@ -2905,6 +2939,7 @@ comstart(tp)
 				com->obufq.l_next = &com->obufs[0];
 				com->state |= CS_BUSY;
 			}
+			COM_UNLOCK();
 			enable_intr();
 		}
 		if (tp->t_outq.c_cc != 0 && !com->obufs[1].l_queued) {
@@ -2914,6 +2949,7 @@ comstart(tp)
 			com->obufs[1].l_next = NULL;
 			com->obufs[1].l_queued = TRUE;
 			disable_intr();
+			COM_LOCK();
 			if (com->state & CS_BUSY) {
 				qp = com->obufq.l_next;
 				while ((next = qp->l_next) != NULL)
@@ -2925,13 +2961,16 @@ comstart(tp)
 				com->obufq.l_next = &com->obufs[1];
 				com->state |= CS_BUSY;
 			}
+			COM_UNLOCK();
 			enable_intr();
 		}
 		tp->t_state |= TS_BUSY;
 	}
 	disable_intr();
+	COM_LOCK();
 	if (com->state >= (CS_BUSY | CS_TTGO))
 		siointr1(com);	/* fake interrupt to start output */
+	COM_UNLOCK();
 	enable_intr();
 #ifdef PC98
 /*		if(IS_8251(com->pc98_if_type))
@@ -2952,6 +2991,7 @@ siostop(tp, rw)
 	if (com->gone)
 		return;
 	disable_intr();
+	COM_LOCK();
 	if (rw & FWRITE) {
 		if (com->hasfifo)
 #ifdef COM_ESP
@@ -2980,6 +3020,7 @@ siostop(tp, rw)
 		com_events -= (com->iptr - com->ibuf);
 		com->iptr = com->ibuf;
 	}
+	COM_UNLOCK();
 	enable_intr();
 	comstart(tp);
 }
@@ -3040,6 +3081,7 @@ commctl(com, bits, how)
 	if (com->gone)
 		return(0);
 	disable_intr();
+	COM_LOCK();
 	switch (how) {
 	case DMSET:
 		outb(com->modem_ctl_port,
@@ -3052,6 +3094,7 @@ commctl(com, bits, how)
 		outb(com->modem_ctl_port, com->mcr_image &= ~mcr);
 		break;
 	}
+	COM_UNLOCK();
 	enable_intr();
 	return (0);
 }
@@ -3111,7 +3154,9 @@ comwakeup(chan)
 		if (com != NULL && !com->gone
 		    && (com->state >= (CS_BUSY | CS_TTGO) || com->poll)) {
 			disable_intr();
+			COM_LOCK();
 			siointr1(com);
+			COM_UNLOCK();
 			enable_intr();
 		}
 	}
@@ -3135,8 +3180,10 @@ comwakeup(chan)
 			u_long	total;
 
 			disable_intr();
+			COM_LOCK();
 			delta = com->delta_error_counts[errnum];
 			com->delta_error_counts[errnum] = 0;
+			COM_UNLOCK();
 			enable_intr();
 			if (delta == 0)
 				continue;
diff --git a/sys/pc98/i386/trap.c b/sys/pc98/i386/trap.c
index 4727c1a02099..7d4df49366a2 100644
--- a/sys/pc98/i386/trap.c
+++ b/sys/pc98/i386/trap.c
@@ -35,7 +35,7 @@
  * SUCH DAMAGE.
  *
  *	from: @(#)trap.c	7.4 (Berkeley) 5/13/91
- *	$Id: trap.c,v 1.29 1997/08/13 11:00:09 kato Exp $
+ *	$Id: trap.c,v 1.30 1997/08/18 11:29:58 kato Exp $
  */
 
 /*
@@ -828,6 +828,14 @@ trap_fatal(frame)
 		printf("bio ");
 	if (cpl == 0)
 		printf("none");
+#ifdef SMP
+/**
+ *  XXX FIXME:
+ *	we probably SHOULD have stopped the other CPUs before now!
+ *	another CPU COULD have been touching cpl at this moment...
+ */
+	printf(" <- SMP: XXX");
+#endif
 	printf("\n");
 
 #ifdef KDB
diff --git a/sys/pc98/pc98/sio.c b/sys/pc98/pc98/sio.c
index 9fef976e4074..2d26234fe706 100644
--- a/sys/pc98/pc98/sio.c
+++ b/sys/pc98/pc98/sio.c
@@ -31,7 +31,7 @@
  * SUCH DAMAGE.
  *
  *	from: @(#)com.c	7.5 (Berkeley) 5/16/91
- *	$Id: sio.c,v 1.31 1997/07/21 13:11:12 kato Exp $
+ *	$Id: sio.c,v 1.32 1997/08/06 09:42:57 kato Exp $
  */
 
 #include "opt_comconsole.h"
@@ -160,6 +160,15 @@
 #include <pccard/slot.h>
 #endif
 
+#ifdef SMP
+#include <machine/smp.h>
+#define COM_LOCK() 	s_lock(&com_lock)
+#define COM_UNLOCK() 	s_unlock(&com_lock)
+#else
+#define COM_LOCK()
+#define COM_UNLOCK()
+#endif /* SMP */
+
 #ifdef APIC_IO
 /*
  * INTs are masked in the (global) IO APIC,
@@ -791,9 +800,11 @@ static int
 card_intr(struct pccard_dev *dp)
 {
 	struct com_s	*com;
+	COM_LOCK();
 	com = com_addr(dp->isahd.id_unit);
 	if (com && !com_addr(dp->isahd.id_unit)->gone)
 		siointr1(com_addr(dp->isahd.id_unit));
+	COM_UNLOCK();
 	return(1);
 }
 #endif /* NCRD > 0 */
@@ -1549,6 +1560,7 @@ open_top:
 		}
 
 		disable_intr();
+		COM_LOCK();
 #ifdef PC98
 		if(IS_8251(com->pc98_if_type)){
 			com_tiocm_bis(com, TIOCM_LE);
@@ -1566,6 +1578,7 @@ open_top:
 #ifdef PC98
 		}
 #endif
+		COM_UNLOCK();
 		enable_intr();
 		/*
 		 * Handle initial DCD.  Callout devices get a fake initial
@@ -1845,7 +1858,9 @@ siointr(unit)
 	int	unit;
 {
 #ifndef COM_MULTIPORT
+	COM_LOCK();
 	siointr1(com_addr(unit));
+	COM_UNLOCK();
 #else /* COM_MULTIPORT */
 	struct com_s    *com;
 	bool_t		possibly_more_intrs;
@@ -1857,6 +1872,7 @@ siointr(unit)
 	 * devices, then the edge from one may be lost because another is
 	 * on.
 	 */
+	COM_LOCK();
 	do {
 		possibly_more_intrs = FALSE;
 		for (unit = 0; unit < NSIO; ++unit) {
@@ -1877,6 +1893,7 @@ siointr(unit)
 			}
 		}
 	} while (possibly_more_intrs);
+	COM_UNLOCK();
 #endif /* COM_MULTIPORT */
 }
 
@@ -2383,6 +2400,7 @@ repeat:
 			 * loop.
 			 */
 			disable_intr();
+			COM_LOCK();
 			incc = com->iptr - com->ibuf;
 			com->iptr = com->ibuf;
 			if (com->state & CS_CHECKMSR) {
@@ -2390,6 +2408,7 @@ repeat:
 				com->state &= ~CS_CHECKMSR;
 			}
 			com_events -= incc;
+			COM_UNLOCK();
 			enable_intr();
 			if (incc != 0)
 				log(LOG_DEBUG,
@@ -2405,6 +2424,7 @@ repeat:
 		} else {
 			buf = ibuf;
 			disable_intr();
+			COM_LOCK();
 			incc = com->iptr - buf;
 			com_events -= incc;
 			if (ibuf == com->ibuf1)
@@ -2440,6 +2460,7 @@ repeat:
 #endif
 				outb(com->modem_ctl_port,
 				     com->mcr_image |= MCR_RTS);
+			COM_UNLOCK();
 			enable_intr();
 			com->ibuf = ibuf;
 		}
@@ -2451,11 +2472,13 @@ repeat:
 			if(!IS_8251(com->pc98_if_type)){
 #endif
 			disable_intr();
+			COM_LOCK();
 			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();
 			enable_intr();
 			if (delta_modem_status & MSR_DCD)
 				(*linesw[tp->t_line].l_modem)
@@ -2466,8 +2489,10 @@ repeat:
 		}
 		if (com->state & CS_ODONE) {
 			disable_intr();
+			COM_LOCK();
 			com_events -= LOTS_OF_EVENTS;
 			com->state &= ~CS_ODONE;
+			COM_UNLOCK();
 			enable_intr();
 			if (!(com->state & CS_BUSY)
 			    && !(com->extra_state & CSE_BUSYCHECK)) {
@@ -2655,9 +2680,11 @@ comparam(tp, t)
 	}
 #endif
 	disable_intr();
+	COM_LOCK();
 retry:
 	com->state &= ~CS_TTGO;
 	txtimeout = tp->t_timeout;
+	COM_UNLOCK();
 	enable_intr();
 #ifdef PC98
 	if(IS_8251(com->pc98_if_type)){
@@ -2685,7 +2712,9 @@ retry:
 		if (error != 0 && error != EAGAIN) {
 			if (!(tp->t_state & TS_TTSTOP)) {
 				disable_intr();
+				COM_LOCK();
 				com->state |= CS_TTGO;
+				COM_UNLOCK();
 				enable_intr();
 			}
 			splx(s);
@@ -2694,6 +2723,7 @@ retry:
 	}
 
 	disable_intr();		/* very important while com_data is hidden */
+	COM_LOCK();
 
 	/*
 	 * XXX - clearing CS_TTGO is not sufficient to stop further output,
@@ -2814,6 +2844,7 @@ retry:
 	if (com->state >= (CS_BUSY | CS_TTGO))
 		siointr1(com);
 
+	COM_UNLOCK();
 	enable_intr();
 	splx(s);
 	comstart(tp);
@@ -2835,6 +2866,7 @@ comstart(tp)
 	com = com_addr(unit);
 	s = spltty();
 	disable_intr();
+	COM_LOCK();
 	if (tp->t_state & TS_TTSTOP)
 		com->state &= ~CS_TTGO;
 	else
@@ -2874,6 +2906,7 @@ comstart(tp)
 #endif
 			outb(com->modem_ctl_port, com->mcr_image |= MCR_RTS);
 	}
+	COM_UNLOCK();
 	enable_intr();
 	if (tp->t_state & (TS_TIMEOUT | TS_TTSTOP)) {
 #ifdef PC98
@@ -2894,6 +2927,7 @@ comstart(tp)
 			com->obufs[0].l_next = NULL;
 			com->obufs[0].l_queued = TRUE;
 			disable_intr();
+			COM_LOCK();
 			if (com->state & CS_BUSY) {
 				qp = com->obufq.l_next;
 				while ((next = qp->l_next) != NULL)
@@ -2905,6 +2939,7 @@ comstart(tp)
 				com->obufq.l_next = &com->obufs[0];
 				com->state |= CS_BUSY;
 			}
+			COM_UNLOCK();
 			enable_intr();
 		}
 		if (tp->t_outq.c_cc != 0 && !com->obufs[1].l_queued) {
@@ -2914,6 +2949,7 @@ comstart(tp)
 			com->obufs[1].l_next = NULL;
 			com->obufs[1].l_queued = TRUE;
 			disable_intr();
+			COM_LOCK();
 			if (com->state & CS_BUSY) {
 				qp = com->obufq.l_next;
 				while ((next = qp->l_next) != NULL)
@@ -2925,13 +2961,16 @@ comstart(tp)
 				com->obufq.l_next = &com->obufs[1];
 				com->state |= CS_BUSY;
 			}
+			COM_UNLOCK();
 			enable_intr();
 		}
 		tp->t_state |= TS_BUSY;
 	}
 	disable_intr();
+	COM_LOCK();
 	if (com->state >= (CS_BUSY | CS_TTGO))
 		siointr1(com);	/* fake interrupt to start output */
+	COM_UNLOCK();
 	enable_intr();
 #ifdef PC98
 /*		if(IS_8251(com->pc98_if_type))
@@ -2952,6 +2991,7 @@ siostop(tp, rw)
 	if (com->gone)
 		return;
 	disable_intr();
+	COM_LOCK();
 	if (rw & FWRITE) {
 		if (com->hasfifo)
 #ifdef COM_ESP
@@ -2980,6 +3020,7 @@ siostop(tp, rw)
 		com_events -= (com->iptr - com->ibuf);
 		com->iptr = com->ibuf;
 	}
+	COM_UNLOCK();
 	enable_intr();
 	comstart(tp);
 }
@@ -3040,6 +3081,7 @@ commctl(com, bits, how)
 	if (com->gone)
 		return(0);
 	disable_intr();
+	COM_LOCK();
 	switch (how) {
 	case DMSET:
 		outb(com->modem_ctl_port,
@@ -3052,6 +3094,7 @@ commctl(com, bits, how)
 		outb(com->modem_ctl_port, com->mcr_image &= ~mcr);
 		break;
 	}
+	COM_UNLOCK();
 	enable_intr();
 	return (0);
 }
@@ -3111,7 +3154,9 @@ comwakeup(chan)
 		if (com != NULL && !com->gone
 		    && (com->state >= (CS_BUSY | CS_TTGO) || com->poll)) {
 			disable_intr();
+			COM_LOCK();
 			siointr1(com);
+			COM_UNLOCK();
 			enable_intr();
 		}
 	}
@@ -3135,8 +3180,10 @@ comwakeup(chan)
 			u_long	total;
 
 			disable_intr();
+			COM_LOCK();
 			delta = com->delta_error_counts[errnum];
 			com->delta_error_counts[errnum] = 0;
+			COM_UNLOCK();
 			enable_intr();
 			if (delta == 0)
 				continue;