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atomic: return old value, not boolean

--- a/atomic-amd64.s

+++ b/atomic-amd64.s

@@ -34,22 +34,13 @@

 	MOVL	c+8(FP), AX

 	MOVL	v+16(FP), BX

 	LOCK; CMPXCHGL	BX, (RARG)

-	MOVL	$1, AX				/* use CMOVLEQ etc. here? */

-	JNZ	fail32

 	RET

-fail32:

-	DECL	AX

-	RET

+

 TEXT acasv+0(SB),1,$0

 TEXT acasp+0(SB),1,$0

 	MOVQ	c+8(FP), AX

 	MOVQ	v+16(FP), BX

 	LOCK; CMPXCHGQ BX, (RARG)

-	MOVL	$1, AX				/* use CMOVLEQ etc. here? */

-	JNZ	fail64

-	RET

-fail64:

-	DECL	AX

 	RET

 /* barriers (do we want to distinguish types?) */

--- a/blk.c

+++ b/blk.c

@@ -35,7 +35,7 @@

 	while(1){

 		ov = agetl(&b->flag);

 		nv = ov | f;

-		if(acasl(&b->flag, ov, nv))

+		if(acasl(&b->flag, ov, nv) == ov)

 			break;

 	}

 }

@@ -48,7 +48,7 @@

 	while(1){

 		ov = agetl(&b->flag);

 		nv = ov & ~f;

-		if(acasl(&b->flag, ov, nv))

+		if(acasl(&b->flag, ov, nv) == ov)

 			break;

 	}

 }

--- a/fs.c

+++ b/fs.c

@@ -150,7 +150,7 @@

 	long v;

 	v = agetl(&c->count);

-	if(v == 0 || !acasl(&c->count, v, v-1))

+	if(v == 0 || acasl(&c->count, v, v-1) != v)

 		semacquire(&c->count, 1);

 	lock(&c->rl);

 	a = *c->rp;

@@ -167,7 +167,7 @@

 	long v;

 	v = agetl(&c->avail);

-	if(v == 0 || !acasl(&c->avail, v, v-1))

+	if(v == 0 || acasl(&c->avail, v, v-1) != v)

 		semacquire(&c->avail, 1);

 	lock(&c->wl);

 	*c->wp = m;

@@ -1464,6 +1464,7 @@

 	Xdir d;

 	int nm;

+	e = nil;

 	if(okname(m->name) == -1){

 		rerror(m, Ename);

 		return;