diff --git a/emu/Makefile b/emu/Makefile
index 1f5a7b0..13c0c11 100644
--- a/emu/Makefile
+++ b/emu/Makefile
@@ -1,5 +1,5 @@
-SRC=emu.c util.c cmd.c apr.c mem.c tty.c pt.c dc.c dt.c netmem.c ../tools/pdp6common.c
-H=pdp6.h ../tools/pdp6common.h
+SRC=emu.c util.c threading.c cmd.c apr.c mem.c tty.c pt.c dc.c dt.c netmem.c ../tools/pdp6common.c
+H=pdp6.h ../tools/pdp6common.h threading.h
 # clang
 #CFLAGS= -Wno-shift-op-parentheses -Wno-logical-op-parentheses \
 #        -Wno-bitwise-op-parentheses
diff --git a/emu/apr.c b/emu/apr.c
index 9328def..7d1a6c1 100644
--- a/emu/apr.c
+++ b/emu/apr.c
@@ -224,7 +224,7 @@ Device*
 makeapr(int argc, char *argv[])
 {
 	Apr *apr;
-	Thread th;
+	Task t;
 
 	apr = malloc(sizeof(Apr));
 	memset(apr, 0, sizeof(Apr));
@@ -237,8 +237,8 @@ makeapr(int argc, char *argv[])
 	apr->iobus.dev[CPA] = (Busdev){ apr, wake_cpa, 0 };
 	apr->iobus.dev[PI] = (Busdev){ apr, wake_pi, 0 };
 
-	th = (Thread){ nil, aprcycle, apr, 1, 0 };
-	addthread(th);
+	t = (Task){ nil, aprcycle, apr, 1, 0 };
+	addtask(t);
 
 	return &apr->dev;
 }
diff --git a/emu/args.h b/emu/args.h
index a73082f..830e3a1 100644
--- a/emu/args.h
+++ b/emu/args.h
@@ -1,4 +1,6 @@
+#ifndef USED
 #define USED(x) ((void)x)
+#endif
 #define SET(x) ((x)=0)
 
 extern char *argv0;
diff --git a/emu/cmd.c b/emu/cmd.c
index dcd9205..d04f131 100644
--- a/emu/cmd.c
+++ b/emu/cmd.c
@@ -726,8 +726,11 @@ commandline(char *line)
 	}
 }
 
+/* If there is no channel, execute immediately.
+ * Otherwise send line through channel so it can
+ * be executed synchronously in the simulation thread. */
 void
-cli(FILE *in)
+cli(FILE *in, Channel **c)
 {
 	size_t len;
 	char *line;
@@ -740,15 +743,20 @@ cli(FILE *in)
 			printf("> ");
 		if(getline(&line, &len, in) < 0)
 			return;
-		commandline(line);
-		free(line);
+		if(c){
+			chansend(c[0], &line);
+			chanrecv(c[1], &line);	// wait for completion
+		}else{
+			commandline(line);
+			free(line);
+		}
 	}
 }
 
 void*
 cmdthread(void *p)
 {
-	cli(stdin);
+	cli(stdin, p);
 	quit(0);
 	return nil;
 }
diff --git a/emu/dt.c b/emu/dt.c
index 04eedfc..4560d22 100644
--- a/emu/dt.c
+++ b/emu/dt.c
@@ -776,7 +776,7 @@ Device*
 makedt(int argc, char *argv[])
 {
 	Dt551 *dt;
-	Thread th;
+	Task t;
 
 	dt = malloc(sizeof(Dt551));
 	memset(dt, 0, sizeof(Dt551));
@@ -789,8 +789,8 @@ makedt(int argc, char *argv[])
 
 	// should have 30000 cycles per second, so one every 33μs
 	// APR at 1 has an approximate cycle time of 200-300ns
-	th = (Thread){ nil, dtcycle, dt, 150, 0 };
-	addthread(th);
+	t = (Task){ nil, dtcycle, dt, 150, 0 };
+	addtask(t);
 
 	return &dt->dev;
 }
diff --git a/emu/emu.c b/emu/emu.c
index fc591be..9d55f79 100644
--- a/emu/emu.c
+++ b/emu/emu.c
@@ -39,30 +39,30 @@ err(char *fmt, ...)
 }
 
 
-Thread *threads;
+Task *tasks;
 
 void
-addthread(Thread th)
+addtask(Task t)
 {
-	Thread *p;
-	p = malloc(sizeof(Thread));
-	*p = th;
-	p->next = threads;
-	threads = p;
+	Task *p;
+	p = malloc(sizeof(Task));
+	*p = t;
+	p->next = tasks;
+	tasks = p;
 }
 
 void*
 simthread(void *p)
 {
-	Thread *th;
+	Task *t;
 
 	printf("[simthread] start\n");
 	for(;;)
-		for(th = threads; th; th = th->next){
-			th->cnt++;
-			if(th->cnt == th->freq){
-				th->cnt = 0;
-				th->f(th->arg);
+		for(t = tasks; t; t = t->next){
+			t->cnt++;
+			if(t->cnt == t->freq){
+				t->cnt = 0;
+				t->f(t->arg);
 			}
 		}
 	err("can't happen");
@@ -104,10 +104,26 @@ dofile(const char *path)
 		printf("Couldn't open file %s\n", path);
 		return;
 	}
-	cli(f);
+	cli(f, nil);
 	fclose(f);
 }
 
+/* Task for simulation.
+ * Execute commands synchronously. */
+void
+readcmdchan(void *p)
+{
+	Channel **c;
+	char *line;
+
+	c = p;
+	if(channbrecv(c[0], &line) == 1){
+		commandline(line);
+		free(line);
+		chansend(c[1], &line);
+	}
+}
+
 void
 quit(int code)
 {
diff --git a/emu/main_panel.c b/emu/main_panel.c
index 167a4c8..0407e8f 100644
--- a/emu/main_panel.c
+++ b/emu/main_panel.c
@@ -2,7 +2,6 @@
 #include <stdarg.h>
 #include <SDL.h>
 #include <SDL_image.h>
-#include <pthread.h>
 #include "args.h"
 
 typedef struct Point Point;
@@ -516,7 +515,7 @@ usage(void)
 }
 
 int
-main(int argc, char *argv[])
+threadmain(int argc, char *argv[])
 {
 	SDL_Surface *screen;
 	SDL_Event ev;
@@ -525,8 +524,9 @@ main(int argc, char *argv[])
 	Element *e;
 	int i;
 	int w, h;
-	pthread_t cmd_thread, sim_thread;
 	const char *outfile;
+	Channel *cmdchans[2];
+	Task t;
 
 	Apr *apr;
 	Ptr *ptr;
@@ -644,8 +644,12 @@ main(int argc, char *argv[])
 	ptr = (Ptr*)getdevice("ptr");
 	ptp = (Ptp*)getdevice("ptp");
 
-	pthread_create(&sim_thread, nil, simthread, apr);
-	pthread_create(&cmd_thread, nil, cmdthread, nil);
+	cmdchans[0] = chancreate(sizeof(char*), 1);
+	cmdchans[1] = chancreate(sizeof(void*), 1);
+	t = (Task){ nil, readcmdchan, cmdchans, 10, 0 };
+	addtask(t);
+	threadcreate(simthread, nil);
+	threadcreate(cmdthread, cmdchans);
 
 	for(;;){
 		while(SDL_PollEvent(&ev))
diff --git a/emu/main_serial.c b/emu/main_serial.c
index 99dc302..f63262a 100644
--- a/emu/main_serial.c
+++ b/emu/main_serial.c
@@ -1,6 +1,5 @@
 #include "pdp6.h"
 #include <stdarg.h>
-#include <pthread.h>
 #include "args.h"
 
 #include <fcntl.h>
@@ -154,12 +153,13 @@ usage(void)
 }
 
 int
-main(int argc, char *argv[])
+threadmain(int argc, char *argv[])
 {
-	pthread_t cmd_thread, sim_thread;
 	const char *outfile;
 	const char *panelfile;
 	int fd;
+	Channel *cmdchans[2];
+	Task t;
 
 	Apr *apr;
 	Ptr *ptr;
@@ -189,8 +189,12 @@ main(int argc, char *argv[])
 	apr = (Apr*)getdevice("apr");
 	ptr = (Ptr*)getdevice("ptr");
 
-	pthread_create(&sim_thread, nil, simthread, apr);
-	pthread_create(&cmd_thread, nil, cmdthread, nil);
+	cmdchans[0] = chancreate(sizeof(char*), 1);
+	cmdchans[1] = chancreate(sizeof(void*), 1);
+	t = (Task){ nil, readcmdchan, cmdchans, 10, 0 };
+	addtask(t);
+	threadcreate(simthread, nil);
+	threadcreate(cmdthread, cmdchans);
 
 	if(panelfile){
 		fd = open(panelfile, O_RDWR);
diff --git a/emu/mem_0 b/emu/mem_0
index cce9b0b..a5ed455 100644
--- a/emu/mem_0
+++ b/emu/mem_0
@@ -2157,7 +2157,7 @@
 721200000000
 321600037451
 542200037447
-322600037066
+322600037402
 254000037402
 563000033777
 254000034000
@@ -2212,7 +2212,7 @@
 253400037524
 321400037541
 323500037470
-201400000055
+201400037536
 332010037177
 254000037470
 336000000012
diff --git a/emu/netmem.c b/emu/netmem.c
index 9e8f2c9..a2e7d42 100644
--- a/emu/netmem.c
+++ b/emu/netmem.c
@@ -91,7 +91,7 @@ makenetmem(int argc, char *argv[])
 	int port;
 	Netmem *nm;
 	Device *apr;
-	Thread th;
+	Task t;
 
 	nm = malloc(sizeof(Netmem));
 	memset(nm, 0, sizeof(Netmem));
@@ -120,8 +120,8 @@ makenetmem(int argc, char *argv[])
 		printf("couldn't connect\n");
 	printf("netmem fd: %d\n", nm->fd);
 
-	th = (Thread){ nil, netmemcycle, nm, 50, 0 };
-	addthread(th);
+	t = (Task){ nil, netmemcycle, nm, 50, 0 };
+	addtask(t);
 
 	return &nm->dev;
 }
diff --git a/emu/pdp6.h b/emu/pdp6.h
index 4ed3a65..fc23476 100644
--- a/emu/pdp6.h
+++ b/emu/pdp6.h
@@ -6,6 +6,7 @@
 #include <ctype.h>
 #include <assert.h>
 #include "../tools/pdp6common.h"
+#include "threading.h"
 
 #define nelem(a) (sizeof(a)/sizeof(a[0]))
 #define nil NULL
@@ -33,7 +34,9 @@ int readn(int fd, void *data, int n);
 int dial(const char *host, int port);
 
 void quit(int code);
-void cli(FILE *f);
+void commandline(char *line);
+void cli(FILE *f, Channel **c);
+void readcmdchan(void *p);
 void *cmdthread(void *);
 void *simthread(void *p);
 void dofile(const char *path);
@@ -84,18 +87,18 @@ typedef struct IOBus IOBus;
 typedef struct Apr Apr;
 
 
-typedef struct Thread Thread;
-struct Thread
+typedef struct Task Task;
+struct Task
 {
-	Thread *next;	/* link to next thread */
+	Task *next;	/* link to next task */
 	void (*f)(void*);
 	void *arg;
-	int freq;	/* how often the thread is serviced */
+	int freq;	/* how often the task is serviced */
 	int cnt;
 };
 
-extern Thread *threads;
-void addthread(Thread th);
+extern Task *tasks;
+void addtask(Task t);
 
 typedef struct Device Device;
 struct Device
diff --git a/emu/pt.c b/emu/pt.c
index 025461a..2bcd015 100644
--- a/emu/pt.c
+++ b/emu/pt.c
@@ -240,7 +240,7 @@ Device*
 makeptp(int argc, char *argv[])
 {
 	Ptp *ptp;
-	Thread th;
+	Task t;
 
 	ptp = malloc(sizeof(Ptp));
 	memset(ptp, 0, sizeof(Ptp));
@@ -251,8 +251,8 @@ makeptp(int argc, char *argv[])
 	ptp->dev.ioconnect = ptpioconnect;
 	ptp->fd = -1;
 
-	th = (Thread){ nil, ptpcycle, ptp, 1000, 0 };
-	addthread(th);
+	t = (Task){ nil, ptpcycle, ptp, 1000, 0 };
+	addtask(t);
 	return &ptp->dev;
 }
 
@@ -260,7 +260,7 @@ Device*
 makeptr(int argc, char *argv[])
 {
 	Ptr *ptr;
-	Thread th;
+	Task t;
 
 	ptr = malloc(sizeof(Ptr));
 	memset(ptr, 0, sizeof(Ptr));
@@ -271,7 +271,7 @@ makeptr(int argc, char *argv[])
 	ptr->dev.ioconnect = ptrioconnect;
 	ptr->fd = -1;
 
-	th = (Thread){ nil, ptrcycle, ptr, 1000, 0 };
-	addthread(th);
+	t = (Task){ nil, ptrcycle, ptr, 1000, 0 };
+	addtask(t);
 	return &ptr->dev;
 }
diff --git a/emu/test_dt.c b/emu/test_dt.c
index 90c399d..d0a698b 100644
--- a/emu/test_dt.c
+++ b/emu/test_dt.c
@@ -6,7 +6,7 @@ Dx555 *dx;
 IOBus iobus;
 IOBus *bus = &iobus;
 int pireq;
-Thread dtthread;
+Task dttask;
 
 void
 setreq(IOBus *bus, int dev, u8 pia)
@@ -16,9 +16,9 @@ setreq(IOBus *bus, int dev, u8 pia)
 }
 
 void
-addthread(Thread th)
+addtask(Task t)
 {
-	dtthread = th;
+	dttask = t;
 }
 
 
@@ -203,7 +203,7 @@ fwdtest_w(void)
 	cono(bus, DC, DARQ|DBRQ|OUT|CHMOD_6|DEV1|7);
 	cono(bus, UTC, SEL|GO|FWD|DLY3|FN_WBN|DEV1|0);
 	while(dt->ut_go){
-		dtthread.f(dt);
+		dttask.f(dt);
 		if(pireq == 7){
 			if(bufsz > 0){
 				w = bufp[--bufsz];
@@ -228,7 +228,7 @@ revtest_w(void)
 	cono(bus, DC, DARQ|DBRQ|OUT|CHMOD_6|DEV1|7);
 	cono(bus, UTC, SEL|GO|REV|DLY3|FN_WD|DEV1|0);
 	while(dt->ut_go){
-		dtthread.f(dt);
+		dttask.f(dt);
 		if(pireq == 7){
 			if(bufsz > 0){
 				w = bufp[--bufsz];
@@ -251,7 +251,7 @@ fwdtest_r(void)
 	cono(bus, DC, DBDAMOVE|IN|CHMOD_6|DEV1|7);
 	cono(bus, UTC, SEL|GO|FWD|DLY3|FN_RD|DEV1|0);
 	while(dt->ut_go){
-		dtthread.f(dt);
+		dttask.f(dt);
 		if(pireq == 7){
 			w = datai(bus, DC);
 			printf("DC got: %012lo\n", w);
@@ -271,7 +271,7 @@ revtest_r(void)
 	cono(bus, DC, DBDAMOVE|IN|CHMOD_6|DEV1|7);
 	cono(bus, UTC, SEL|GO|REV|DLY3|FN_RD|DEV1|0);
 	while(dt->ut_go){
-		dtthread.f(dt);
+		dttask.f(dt);
 		if(pireq == 7){
 			w = datai(bus, DC);
 			printf("DC got: %012lo\n", w);
@@ -293,7 +293,7 @@ fmttest(void)
 	cono(bus, DC, DARQ|DBRQ|OUT|CHMOD_6|DEV1|7);
 	cono(bus, UTC, SEL|GO|FWD|DLY3|FN_WTM|DEV1|0);
 	while(dt->ut_go){
-		dtthread.f(dt);
+		dttask.f(dt);
 		if(pireq == 7){
 			if(bufsz > 0){
 				--bufsz;
diff --git a/emu/threading.c b/emu/threading.c
new file mode 100644
index 0000000..3cb9f0f
--- /dev/null
+++ b/emu/threading.c
@@ -0,0 +1,357 @@
+#include "threading.h"
+#include <assert.h>
+
+#define USED(x) (void)(x)
+
+/*
+ * Locks
+ */
+
+static pthread_mutex_t initmutex = PTHREAD_MUTEX_INITIALIZER;
+
+static void
+lockinit(Lock *lk)
+{
+	pthread_mutexattr_t attr;
+
+	pthread_mutex_lock(&initmutex);
+	if(lk->init == 0){
+		pthread_mutexattr_init(&attr);
+		pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_NORMAL);
+		pthread_mutex_init(&lk->mutex, &attr);
+		pthread_mutexattr_destroy(&attr);
+		lk->init = 1;
+	}
+	pthread_mutex_unlock(&initmutex);
+}
+
+void
+lock(Lock *lk)
+{
+	if(!lk->init)
+		lockinit(lk);
+	if(pthread_mutex_lock(&lk->mutex) != 0)
+		abort();
+}
+
+int
+canlock(Lock *lk)
+{
+	int r;
+
+	if(!lk->init)
+		lockinit(lk);
+	r = pthread_mutex_trylock(&lk->mutex);
+	if(r == 0)
+		return 1;
+	if(r == EBUSY)
+		return 0;
+	abort();
+}
+
+void
+unlock(Lock *lk)
+{
+	if(pthread_mutex_unlock(&lk->mutex) != 0)
+		abort();
+}
+
+
+
+static void
+rendinit(Rendez *r)
+{
+	pthread_condattr_t attr;
+
+	pthread_mutex_lock(&initmutex);
+	if(r->init == 0){
+		pthread_condattr_init(&attr);
+		pthread_cond_init(&r->cond, &attr);
+		pthread_condattr_destroy(&attr);
+		r->init = 1;
+	}
+	pthread_mutex_unlock(&initmutex);
+}
+
+void
+rsleep(Rendez *r)
+{
+	if(!r->init)
+		rendinit(r);
+	if(pthread_cond_wait(&r->cond, &r->l->mutex) != 0)
+		abort();
+}
+
+void
+rwakeup(Rendez *r)
+{
+	if(pthread_cond_signal(&r->cond) != 0)
+		abort();
+}
+
+void
+rwakeupall(Rendez *r)
+{
+	if(pthread_cond_broadcast(&r->cond) != 0)
+		abort();
+}
+
+
+/*
+ * Threads
+ */
+
+
+static Lock idlock;
+static pthread_t *threads;
+static int numthreads;
+static int maxthreads;
+
+static __thread int myid;
+static __thread void *mypointer;
+
+static int
+addthreadid(void)
+{
+	int id;
+
+	if(numthreads >= maxthreads){
+		maxthreads += 64;
+		threads = realloc(threads, maxthreads*sizeof(*threads));
+	}
+	id = numthreads++;
+	threads[id] = 0;
+	return id;
+}
+
+static pthread_t
+gethandle(int id)
+{
+	pthread_t th;
+	lock(&idlock);
+	th = threads[id];
+	unlock(&idlock);
+	return th;
+}
+
+struct ThreadArg
+{
+	int id;
+	void *(*f)(void*);
+	void *arg;
+};
+
+static void*
+trampoline(void *p)
+{
+	struct ThreadArg *args;
+	void *(*f)(void*);
+	void *arg;
+
+	args = p;
+	myid = args->id;
+	f = args->f;
+	arg = args->arg;
+	free(args);
+	return f(arg);
+}
+
+int
+threadcreate(void *(*f)(void*), void *arg)
+{
+	struct ThreadArg *args;
+	int id;
+
+	lock(&idlock);
+	id = addthreadid();
+	args = malloc(sizeof(*args));
+	args->id = id;
+	args->f = f;
+	args->arg = arg;
+	pthread_create(&threads[id], nil, trampoline, args);
+	unlock(&idlock);
+	return id;
+}
+
+void
+threadexits(void *ret)
+{
+	pthread_exit(ret);
+}
+
+int
+threadid(void)
+{
+	return myid;
+}
+
+void**
+threaddata(void)
+{
+	return &mypointer;
+}
+
+void
+threadkill(int id)
+{
+	assert(id >= 0 && id < numthreads);
+	pthread_cancel(gethandle(id));
+}
+
+void
+threadwait(int id)
+{
+	pthread_join(gethandle(id), nil);
+}
+
+int
+main(int argc, char *argv[])
+{
+	int id;
+
+	id = addthreadid();
+	threads[id] = pthread_self();
+	return threadmain(argc, argv);
+}
+
+
+/*
+ * Channels
+ */
+
+
+Channel*
+chancreate(int elemsize, int bufsize)
+{
+	Channel *c;
+
+	c = malloc(sizeof(Channel) + bufsize*elemsize);
+	if(c == nil)
+		return nil;
+	memset(c, 0, sizeof(Channel));
+	c->elemsize = elemsize;
+	c->bufsize = bufsize;
+	c->nbuf = 0;
+	c->buf = (uchar*)(c+1);
+	c->full.l = &c->lock;
+	c->empty.l = &c->lock;
+	return c;
+}
+
+void
+chanclose(Channel *c)
+{
+	lock(&c->lock);
+	c->closed = 1;
+	rwakeupall(&c->full);
+	rwakeupall(&c->empty);
+	unlock(&c->lock);
+}
+
+void
+chanfree(Channel *c)
+{
+	// TODO: don't free chans still in use
+	free(c);
+}
+
+static int cansend(Channel *c) { return c->nbuf < c->bufsize; }
+static int canrecv(Channel *c) { return c->nbuf > 0; }
+
+static void
+chansend_(Channel *c, void *p)
+{
+	uchar *pp;
+
+	assert(cansend(c));
+	pp = c->buf + (c->off+c->nbuf)%c->bufsize * c->elemsize;
+	memmove(pp, p, c->elemsize);
+	c->nbuf++;
+}
+
+static void
+chanrecv_(Channel *c, void *p)
+{
+	uchar *pp;
+
+	assert(canrecv(c));
+	pp = c->buf + c->off*c->elemsize;
+	memmove(p, pp, c->elemsize);
+	c->nbuf--;
+	if(++c->off == c->bufsize)
+		c->off = 0;
+}
+
+int
+chansend(Channel *c, void *p)
+{
+	lock(&c->lock);
+	while(!(c->closed || cansend(c)))
+		rsleep(&c->full);
+	/* closed or can send */
+	if(c->closed){
+		/* can never send to closed chan */
+		unlock(&c->lock);
+		return -1;
+	}
+	chansend_(c, p);
+	rwakeup(&c->empty);
+	unlock(&c->lock);
+	return 1;
+}
+
+int
+chanrecv(Channel *c, void *p)
+{
+	lock(&c->lock);
+	while(!(c->closed || canrecv(c)))
+		rsleep(&c->empty);
+	/* closed or can receive */
+	if(canrecv(c)){
+		/* can still receive from closed chan */
+		chanrecv_(c, p);
+		rwakeup(&c->full);
+		unlock(&c->lock);
+		return 1;
+	}
+	unlock(&c->lock);
+	return -1;
+}
+
+int
+channbsend(Channel *c, void *p)
+{
+	lock(&c->lock);
+	if(c->closed){
+		/* can never send to closed chan */
+		unlock(&c->lock);
+		return -1;
+	}
+	if(cansend(c)){
+		chansend_(c, p);
+		rwakeup(&c->empty);
+		unlock(&c->lock);
+		return 1;
+	}
+	unlock(&c->lock);
+	return 0;
+}
+
+int
+channbrecv(Channel *c, void *p)
+{
+	lock(&c->lock);
+	if(canrecv(c)){
+		/* can still receive from closed chan */
+		chanrecv_(c, p);
+		rwakeup(&c->full);
+		unlock(&c->lock);
+		return 1;
+	}
+	if(c->closed){
+		unlock(&c->lock);
+		return -1;
+	}
+	unlock(&c->lock);
+	return 0;
+}
diff --git a/emu/threading.h b/emu/threading.h
new file mode 100644
index 0000000..b753eec
--- /dev/null
+++ b/emu/threading.h
@@ -0,0 +1,60 @@
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <pthread.h>
+
+#define nil NULL
+typedef unsigned char uchar;
+typedef unsigned int uint;
+
+typedef struct Lock Lock;
+struct Lock
+{
+	int init;
+	pthread_mutex_t mutex;
+};
+void lock(Lock *lk);
+int canlock(Lock *lk);
+void unlock(Lock *lk);
+
+
+typedef struct Rendez Rendez;
+struct Rendez
+{
+	int init;
+	Lock *l;
+	pthread_cond_t cond;
+};
+void rsleep(Rendez *r);
+void rwakeup(Rendez *r);
+void rwakeupall(Rendez *r);
+
+
+typedef struct Channel Channel;
+struct Channel
+{
+	int bufsize;
+	int elemsize;
+	uchar *buf;
+	int nbuf;
+	int off;
+
+	int closed;
+	Lock lock;
+	Rendez full, empty;
+};
+Channel *chancreate(int elemsize, int bufsize);
+void chanclose(Channel *chan);
+void chanfree(Channel *c);
+int chansend(Channel *c, void *p);
+int chanrecv(Channel *c, void *p);
+int channbsend(Channel *c, void *p);
+int channbrecv(Channel *c, void *p);
+
+int threadmain(int argc, char *argv[]);
+int threadcreate(void *(*f)(void*), void *arg);
+void threadexits(void *ret);
+int threadid(void);
+void **threaddata(void);
+void threadkill(int id);
+void threadwait(int id);
diff --git a/emu/tty.c b/emu/tty.c
index 6f92773..c58cc79 100644
--- a/emu/tty.c
+++ b/emu/tty.c
@@ -136,7 +136,7 @@ Device*
 maketty(int argc, char *argv[])
 {
 	Tty *tty;
-	Thread th;
+	Task t;
 
 	tty = malloc(sizeof(Tty));
 	memset(tty, 0, sizeof(Tty));
@@ -148,8 +148,8 @@ maketty(int argc, char *argv[])
 
 	tty->fd = -1;
 
-	th = (Thread){ nil, ttycycle, tty, 1, 0 };
-	addthread(th);
+	t = (Task){ nil, ttycycle, tty, 1, 0 };
+	addtask(t);
 
 	return &tty->dev;
 }