From 1544f90960275dc9211bde30329c3258e0e1bf38 Mon Sep 17 00:00:00 2001
From: rsc <devnull@localhost>
Date: Sat, 25 Dec 2004 21:56:33 +0000
Subject: New thread library

---
 src/libthread/channel.c | 500 ------------------------------------------------
 1 file changed, 500 deletions(-)
 delete mode 100644 src/libthread/channel.c

(limited to 'src/libthread/channel.c')

diff --git a/src/libthread/channel.c b/src/libthread/channel.c
deleted file mode 100644
index b488dc97..00000000
--- a/src/libthread/channel.c
+++ /dev/null
@@ -1,500 +0,0 @@
-#include "threadimpl.h"
-
-static Lock chanlock;		/* central channel access lock */
-
-static void enqueue(Alt*, Thread*);
-static void dequeue(Alt*);
-static int altexec(Alt*);
-
-int _threadhighnentry;
-int _threadnalt;
-
-static void
-setuserpc(ulong pc)
-{
-	Thread *t;
-
-	t = _threadgetproc()->thread;
-	if(t)
-		t->userpc = pc;
-}
-
-static int
-canexec(Alt *a)
-{
-	int i, otherop;
-	Channel *c;
-
-	c = a->c;
-	/* are there senders or receivers blocked? */
-	otherop = (CHANSND+CHANRCV) - a->op;
-	for(i=0; i<c->nentry; i++)
-		if(c->qentry[i] && c->qentry[i]->op==otherop && c->qentry[i]->thread->altc==nil){
-			_threaddebug(DBGCHAN, "can rendez alt %p chan %p", a, c);
-			return 1;
-		}
-
-	/* is there room in the channel? */
-	if((a->op==CHANSND && c->n < c->s)
-	|| (a->op==CHANRCV && c->n > 0)){
-		_threaddebug(DBGCHAN, "can buffer alt %p chan %p", a, c);
-		return 1;
-	}
-
-	return 0;
-}
-
-static void
-_chanfree(Channel *c)
-{
-	int i, inuse;
-
-	inuse = 0;
-	for(i = 0; i < c->nentry; i++)
-		if(c->qentry[i])
-			inuse = 1;
-	if(inuse)
-		c->freed = 1;
-	else{
-		if(c->qentry)
-			free(c->qentry);
-		free(c);
-	}
-}
-
-void
-chanfree(Channel *c)
-{
-	lock(&chanlock);
-	_chanfree(c);
-	unlock(&chanlock);
-}
-
-int
-chaninit(Channel *c, int elemsize, int elemcnt)
-{
-	if(elemcnt < 0 || elemsize <= 0 || c == nil)
-		return -1;
-	memset(c, 0, sizeof *c);
-	c->e = elemsize;
-	c->s = elemcnt;
-	_threaddebug(DBGCHAN, "chaninit %p", c);
-	return 1;
-}
-
-Channel*
-chancreate(int elemsize, int elemcnt)
-{
-	Channel *c;
-
-	if(elemcnt < 0 || elemsize <= 0)
-		return nil;
-	c = _threadmalloc(sizeof(Channel)+elemsize*elemcnt, 1);
-	c->e = elemsize;
-	c->s = elemcnt;
-	_threaddebug(DBGCHAN, "chancreate %p", c);
-	return c;
-}
-
-static int
-_alt(Alt *alts)
-{
-	Alt *a, *xa;
-	Channel *c;
-	int n;
-	Thread *t;
-
-	/*
-	 * The point of going splhi here is that note handlers
-	 * might reasonably want to use channel operations,
-	 * but that will hang if the note comes while we hold the
-	 * chanlock.  Instead, we delay the note until we've dropped
-	 * the lock.
-	 */
-
-	/*
-	 * T might be nil here -- the scheduler sends on threadwaitchan
-	 * directly (in non-blocking mode, of course!).
-	 */
-	t = _threadgetproc()->thread;
-	if((t && t->moribund) || _threadexitsallstatus)
-		yield();	/* won't return */
-	lock(&chanlock);
-
-	/* test whether any channels can proceed */
-	n = 0;
-	a = nil;
-
-	for(xa=alts; xa->op!=CHANEND && xa->op!=CHANNOBLK; xa++){
-		xa->entryno = -1;
-		if(xa->op == CHANNOP)
-			continue;
-
-		c = xa->c;
-		if(c==nil){
-			unlock(&chanlock);
-			return -1;
-		}
-		if(canexec(xa))
-			if(nrand(++n) == 0)
-				a = xa;
-	}
-
-	if(a==nil){
-		/* nothing can proceed */
-		if(xa->op == CHANNOBLK){
-			unlock(&chanlock);
-			_threadnalt++;
-			return xa - alts;
-		}
-
-		/* enqueue on all channels. */
-		t->altc = nil;
-		for(xa=alts; xa->op!=CHANEND; xa++){
-			if(xa->op==CHANNOP)
-				continue;
-			enqueue(xa, t);
-		}
-
-		/*
-		 * wait for successful rendezvous.
-		 * we can't just give up if the rendezvous
-		 * is interrupted -- someone else might come
-		 * along and try to rendezvous with us, so
-		 * we need to be here.
-		 *
-		 * actually, now we're assuming no interrupts.
-		 */
-	    /*Again:*/
-		t->alt = alts;
-		t->chan = Chanalt;
-		t->altrend.l = &chanlock;
-		_threadsleep(&t->altrend);
-
-		/* dequeue from channels, find selected one */
-		a = nil;
-		c = t->altc;
-		for(xa=alts; xa->op!=CHANEND; xa++){
-			if(xa->op==CHANNOP)
-				continue;
-			if(xa->c == c)
-				a = xa;
-			dequeue(xa);
-		}
-		unlock(&chanlock);
-		if(a == nil){	/* we were interrupted */
-			assert(c==(Channel*)~0);
-			return -1;
-		}
-	}else{
-		altexec(a);	/* unlocks chanlock, does splx */
-	}
-	if(t)
-		t->chan = Channone;
-	return a - alts;
-}
-
-int
-alt(Alt *alts)
-{
-	setuserpc(getcallerpc(&alts));
-	return _alt(alts);
-}
-
-static int
-runop(int op, Channel *c, void *v, int nb)
-{
-	int r;
-	Alt a[2];
-
-	/*
-	 * we could do this without calling alt,
-	 * but the only reason would be performance,
-	 * and i'm not convinced it matters.
-	 */
-	a[0].op = op;
-	a[0].c = c;
-	a[0].v = v;
-	a[1].op = CHANEND;
-	if(nb)
-		a[1].op = CHANNOBLK;
-	switch(r=_alt(a)){
-	case -1:	/* interrupted */
-		return -1;
-	case 1:	/* nonblocking, didn't accomplish anything */
-		assert(nb);
-		return 0;
-	case 0:
-		return 1;
-	default:
-		fprint(2, "ERROR: channel alt returned %d\n", r);
-		abort();
-		return -1;
-	}
-}
-
-int
-recv(Channel *c, void *v)
-{
-	setuserpc(getcallerpc(&c));
-	return runop(CHANRCV, c, v, 0);
-}
-
-int
-nbrecv(Channel *c, void *v)
-{
-	setuserpc(getcallerpc(&c));
-	return runop(CHANRCV, c, v, 1);
-}
-
-int
-send(Channel *c, void *v)
-{
-	setuserpc(getcallerpc(&c));
-	return runop(CHANSND, c, v, 0);
-}
-
-int
-nbsend(Channel *c, void *v)
-{
-	setuserpc(getcallerpc(&c));
-	return runop(CHANSND, c, v, 1);
-}
-
-static void
-channelsize(Channel *c, int sz)
-{
-	if(c->e != sz){
-		fprint(2, "expected channel with elements of size %d, got size %d\n",
-			sz, c->e);
-		abort();
-	}
-}
-
-int
-sendul(Channel *c, ulong v)
-{
-	setuserpc(getcallerpc(&c));
-	channelsize(c, sizeof(ulong));
-	return send(c, &v);
-}
-
-ulong
-recvul(Channel *c)
-{
-	ulong v;
-
-	setuserpc(getcallerpc(&c));
-	channelsize(c, sizeof(ulong));
-	if(runop(CHANRCV, c, &v, 0) < 0)
-		return ~0;
-	return v;
-}
-
-int
-sendp(Channel *c, void *v)
-{
-	setuserpc(getcallerpc(&c));
-	channelsize(c, sizeof(void*));
-	return runop(CHANSND, c, &v, 0);
-}
-
-void*
-recvp(Channel *c)
-{
-	void *v;
-
-	setuserpc(getcallerpc(&c));
-	channelsize(c, sizeof(void*));
-	if(runop(CHANRCV, c, &v, 0) < 0)
-		return nil;
-	return v;
-}
-
-int
-nbsendul(Channel *c, ulong v)
-{
-	setuserpc(getcallerpc(&c));
-	channelsize(c, sizeof(ulong));
-	return runop(CHANSND, c, &v, 1);
-}
-
-ulong
-nbrecvul(Channel *c)
-{
-	ulong v;
-
-	setuserpc(getcallerpc(&c));
-	channelsize(c, sizeof(ulong));
-	if(runop(CHANRCV, c, &v, 1) == 0)
-		return 0;
-	return v;
-}
-
-int
-nbsendp(Channel *c, void *v)
-{
-	setuserpc(getcallerpc(&c));
-	channelsize(c, sizeof(void*));
-	return runop(CHANSND, c, &v, 1);
-}
-
-void*
-nbrecvp(Channel *c)
-{
-	void *v;
-
-	setuserpc(getcallerpc(&c));
-	channelsize(c, sizeof(void*));
-	if(runop(CHANRCV, c, &v, 1) == 0)
-		return nil;
-	return v;
-}
-
-static int
-emptyentry(Channel *c)
-{
-	int i, extra;
-
-	assert((c->nentry==0 && c->qentry==nil) || (c->nentry && c->qentry));
-
-	for(i=0; i<c->nentry; i++)
-		if(c->qentry[i]==nil)
-			return i;
-
-	extra = 16;
-	c->nentry += extra;
-if(c->nentry > _threadhighnentry) _threadhighnentry = c->nentry;
-	c->qentry = realloc((void*)c->qentry, c->nentry*sizeof(c->qentry[0]));
-	if(c->qentry == nil)
-		sysfatal("realloc channel entries: %r");
-	_threadmemset(&c->qentry[i], 0, extra*sizeof(c->qentry[0]));
-	return i;
-}
-
-static void
-enqueue(Alt *a, Thread *t)
-{
-	int i;
-
-	_threaddebug(DBGCHAN, "Queueing alt %p on channel %p", a, a->c);
-	a->thread = t;
-	i = emptyentry(a->c);
-	a->c->qentry[i] = a;
-}
-
-static void
-dequeue(Alt *a)
-{
-	int i;
-	Channel *c;
-
-	c = a->c;
-	for(i=0; i<c->nentry; i++)
-		if(c->qentry[i]==a){
-			_threaddebug(DBGCHAN, "Dequeuing alt %p from channel %p", a, a->c);
-			c->qentry[i] = nil;
-			if(c->freed)
-				_chanfree(c);
-			return;
-		}
-}
-
-static void*
-altexecbuffered(Alt *a, int willreplace)
-{
-	uchar *v;
-	Channel *c;
-
-	c = a->c;
-	/* use buffered channel queue */
-	if(a->op==CHANRCV && c->n > 0){
-		_threaddebug(DBGCHAN, "buffer recv alt %p chan %p", a, c);
-		v = c->v + c->e*(c->f%c->s);
-		if(!willreplace)
-			c->n--;
-		c->f++;
-		return v;
-	}
-	if(a->op==CHANSND && c->n < c->s){
-		_threaddebug(DBGCHAN, "buffer send alt %p chan %p", a, c);
-		v = c->v + c->e*((c->f+c->n)%c->s);
-		if(!willreplace)
-			c->n++;
-		return v;
-	}
-	abort();
-	return nil;
-}
-
-static void
-altcopy(void *dst, void *src, int sz)
-{
-	if(dst){
-		if(src)
-			memmove(dst, src, sz);
-		else
-			_threadmemset(dst, 0, sz);
-	}
-}
-
-static int
-altexec(Alt *a)
-{
-	volatile Alt *b;
-	int i, n, otherop;
-	Channel *c;
-	void *me, *waiter, *buf;
-
-	c = a->c;
-
-	/* rendezvous with others */
-	otherop = (CHANSND+CHANRCV) - a->op;
-	n = 0;
-	b = nil;
-	me = a->v;
-	for(i=0; i<c->nentry; i++)
-		if(c->qentry[i] && c->qentry[i]->op==otherop && c->qentry[i]->thread->altc==nil)
-			if(nrand(++n) == 0)
-				b = c->qentry[i];
-	if(b != nil){
-		_threaddebug(DBGCHAN, "rendez %s alt %p chan %p alt %p", a->op==CHANRCV?"recv":"send", a, c, b);
-		waiter = b->v;
-		if(c->s && c->n){
-			/*
-			 * if buffer is full and there are waiters
-			 * and we're meeting a waiter,
-			 * we must be receiving.
-			 *
-			 * we use the value in the channel buffer,
-			 * copy the waiter's value into the channel buffer
-			 * on behalf of the waiter, and then wake the waiter.
-			 */
-			if(a->op!=CHANRCV)
-				abort();
-			buf = altexecbuffered(a, 1);
-			altcopy(me, buf, c->e);
-			altcopy(buf, waiter, c->e);
-		}else{
-			if(a->op==CHANRCV)
-				altcopy(me, waiter, c->e);
-			else
-				altcopy(waiter, me, c->e);
-		}
-		b->thread->altc = c;
-		_threadwakeup(&b->thread->altrend);
-		_threaddebug(DBGCHAN, "chanlock is %lud", *(ulong*)(void*)&chanlock);
-		_threaddebug(DBGCHAN, "unlocking the chanlock");
-		unlock(&chanlock);
-		return 1;
-	}
-
-	buf = altexecbuffered(a, 0);
-	if(a->op==CHANRCV)
-		altcopy(me, buf, c->e);
-	else
-		altcopy(buf, me, c->e);
-
-	unlock(&chanlock);
-	return 1;
-}
-- 
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