diff --git a/src/libthread/BSD.c b/src/libthread/BSD.c
new file mode 100644
index 0000000..2679cd2
--- /dev/null
+++ b/src/libthread/BSD.c
@@ -0,0 +1,384 @@
+#undef exits
+#undef _exits
+
+extern int __isthreaded;
+
+/*
+ * spin locks
+ */
+extern int _tas(int*);
+
+void
+_threadunlock(Lock *l, ulong pc)
+{
+	USED(pc);
+
+	l->held = 0;
+}
+
+int
+_threadlock(Lock *l, int block, ulong pc)
+{
+	int i;
+
+	USED(pc);
+
+	/* once fast */
+	if(!_tas(&l->held))
+		return 1;
+	if(!block)
+		return 0;
+
+	/* a thousand times pretty fast */
+	for(i=0; i<1000; i++){
+		if(!_tas(&l->held))
+			return 1;
+		sched_yield();
+	}
+	/* increasingly slow */
+	for(i=0; i<10; i++){
+		if(!_tas(&l->held))
+			return 1;
+		usleep(1);
+	}
+	for(i=0; i<10; i++){
+		if(!_tas(&l->held))
+			return 1;
+		usleep(10);
+	}
+	for(i=0; i<10; i++){
+		if(!_tas(&l->held))
+			return 1;
+		usleep(100);
+	}
+	for(i=0; i<10; i++){
+		if(!_tas(&l->held))
+			return 1;
+		usleep(1000);
+	}
+	for(i=0; i<10; i++){
+		if(!_tas(&l->held))
+			return 1;
+		usleep(10*1000);
+	}
+	/* now nice and slow */
+	for(i=0; i<1000; i++){
+		if(!_tas(&l->held))
+			return 1;
+		usleep(100*1000);
+	}
+	/* take your time */
+	while(_tas(&l->held))
+		usleep(1000*1000);
+	return 1;
+}
+
+/*
+ * For libc.
+ */
+
+typedef struct {
+	volatile long	access_lock;
+	volatile long	lock_owner;
+	volatile char	*fname;
+	volatile int	lineno;
+} spinlock_t;
+
+void
+_spinlock(spinlock_t *lk)
+{
+	lock((Lock*)&lk->access_lock);
+}
+
+/*
+ * sleep and wakeup
+ */
+static void
+ign(int x)
+{
+	USED(x);
+}
+
+static void /*__attribute__((constructor))*/
+ignusr1(int restart)
+{
+	struct sigaction sa;
+
+	memset(&sa, 0, sizeof sa);
+	sa.sa_handler = ign;
+	sigemptyset(&sa.sa_mask);
+	sigaddset(&sa.sa_mask, SIGUSR1);
+	if(restart)
+		sa.sa_flags = SA_RESTART;
+	sigaction(SIGUSR1, &sa, nil);
+}
+
+void
+_procsleep(_Procrendez *r)
+{
+	sigset_t mask;
+
+	/*
+	 * Go to sleep.
+	 *
+	 * Block USR1, set the handler to interrupt system calls,
+	 * unlock the vouslock so our waker can wake us,
+	 * and then suspend.
+	 */
+again:
+	r->asleep = 1;
+	r->pid = getpid();
+
+	sigprocmask(SIG_SETMASK, nil, &mask);
+	sigaddset(&mask, SIGUSR1);
+	sigprocmask(SIG_SETMASK, &mask, nil);
+	ignusr1(0);
+	unlock(r->l);
+	sigdelset(&mask, SIGUSR1);
+	sigsuspend(&mask);
+
+	/*
+	 * We're awake.  Make USR1 not interrupt system calls.
+	 */
+	lock(r->l);
+	ignusr1(1);
+	if(r->asleep && r->pid == getpid()){
+		/* Didn't really wake up - signal from something else */
+		goto again;
+	}
+}
+
+void
+_procwakeup(_Procrendez *r)
+{
+	if(r->asleep){
+		r->asleep = 0;
+		assert(r->pid >= 1);
+		kill(r->pid, SIGUSR1);
+	}
+}
+
+void
+_procwakeupandunlock(_Procrendez *r)
+{
+	_procwakeup(r);
+	unlock(r->l);
+}
+
+
+/*
+ * process creation and exit
+ */
+typedef struct Stackfree Stackfree;
+struct Stackfree
+{
+	Stackfree	*next;
+	int	pid;
+};
+static Lock stacklock;
+static Stackfree *stackfree;
+
+static void
+delayfreestack(uchar *stk)
+{
+	Stackfree *sf;
+
+	sf = (Stackfree*)stk;
+	sf->pid = getpid();
+	lock(&stacklock);
+	sf->next = stackfree;
+	stackfree = sf;
+	unlock(&stacklock);
+}
+
+static void
+dofreestacks(void)
+{
+	Stackfree *sf, *last, *next;
+
+	if(stackfree==nil || !canlock(&stacklock))
+		return;
+
+	for(last=nil,sf=stackfree; sf; last=sf,sf=next){
+		next = sf->next;
+		if(sf->pid >= 1 && kill(sf->pid, 0) < 0 && errno == ESRCH){
+			free(sf);
+			if(last)
+				last->next = next;
+			else
+				stackfree = next;
+			sf = last;
+		}
+	}
+	unlock(&stacklock);
+}
+
+static int
+startprocfn(void *v)
+{
+	void **a;
+	uchar *stk;
+	void (*fn)(void*);
+	Proc *p;
+
+	a = (void**)v;
+	fn = a[0];
+	p = a[1];
+	stk = a[2];
+	free(a);
+	p->osprocid = getpid();
+
+	(*fn)(p);
+
+	delayfreestack(stk);
+	_exit(0);
+	return 0;
+}
+
+void
+_procstart(Proc *p, void (*fn)(Proc*))
+{
+	void **a;
+	uchar *stk;
+	int pid;
+
+	dofreestacks();
+	a = malloc(3*sizeof a[0]);
+	if(a == nil)
+		sysfatal("_procstart malloc: %r");
+	stk = malloc(65536);
+	if(stk == nil)
+		sysfatal("_procstart malloc stack: %r");
+
+	a[0] = fn;
+	a[1] = p;
+	a[2] = stk;
+
+	pid = rfork_thread(RFPROC|RFMEM|RFNOWAIT, stk+65536-64, startprocfn, a);
+	if(pid < 0){
+		fprint(2, "_procstart rfork_thread: %r\n");
+		abort();
+	}
+}
+
+static char *threadexitsmsg;
+void
+sigusr2handler(int s)
+{
+/*	fprint(2, "%d usr2 %d\n", time(0), getpid()); */
+	if(threadexitsmsg)
+		_exits(threadexitsmsg);
+}
+
+void
+threadexitsall(char *msg)
+{
+	static int pid[1024];
+	int i, npid, mypid;
+	Proc *p;
+
+	if(msg == nil)
+		msg = "";
+	mypid = getpid();
+	lock(&_threadprocslock);
+	threadexitsmsg = msg;
+	npid = 0;
+	for(p=_threadprocs; p; p=p->next)
+		if(p->osprocid != mypid && p->osprocid >= 1)
+			pid[npid++] = p->osprocid;
+	for(i=0; i<npid; i++)
+		kill(pid[i], SIGUSR2);
+	unlock(&_threadprocslock);
+	exits(msg);
+}
+
+/*
+ * per-process data, indexed by pid
+ */
+typedef struct Perproc Perproc;
+struct Perproc
+{
+	int		pid;
+	Proc	*proc;
+};
+
+static Lock perlock;
+static Perproc perproc[1024];
+#define P ((Proc*)-1)
+
+static Perproc*
+myperproc(void)
+{
+	int i, pid, h;
+	Perproc *p;
+
+	pid = getpid();
+	h = pid%nelem(perproc);
+	for(i=0; i<nelem(perproc); i++){
+		p = &perproc[(i+h)%nelem(perproc)];
+		if(p->pid == pid)
+			return p;
+		if(p->pid == 0){
+			print("found 0 at %d (h=%d)\n", (i+h)%nelem(perproc), h);
+			break;
+		}
+	}
+	fprint(2, "myperproc %d: cannot find self\n", pid);
+	abort();
+	return nil;
+}
+
+static Perproc*
+newperproc(void)
+{
+	int i, pid, h;
+	Perproc *p;
+
+	lock(&perlock);
+	pid = getpid();
+	h = pid%nelem(perproc);
+	for(i=0; i<nelem(perproc); i++){
+		p = &perproc[(i+h)%nelem(perproc)];
+		if(p->pid == pid || p->pid == -1 || p->pid == 0){
+			p->pid = pid;
+			unlock(&perlock);
+			return p;
+		}
+	}
+	fprint(2, "newperproc %d: out of procs\n", pid);
+	abort();
+	return nil;
+}
+
+Proc*
+_threadproc(void)
+{
+	return myperproc()->proc;
+}
+
+void
+_threadsetproc(Proc *p)
+{
+	Perproc *pp;
+
+	if(p)
+		p->osprocid = getpid();
+	pp = newperproc();
+	pp->proc = p;
+	if(p == nil)
+		pp->pid = -1;
+}
+
+void
+_pthreadinit(void)
+{
+	__isthreaded = 1;
+	signal(SIGUSR2, sigusr2handler);
+}
+
+void
+_threadpexit(void)
+{
+	_exit(0);
+}
+