runtime: remove singleproc var

It was needed for the old scheduler,
because there temporary could be more threads than gomaxprocs.
In the new scheduler gomaxprocs is always respected.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/12438043

src/pkg/runtime/mgc0.c

@@ -2347,7 +2347,7 @@ runtime·markallocated(void *v, uintptr n, bool noptr)
 		bits = (obits & ~(bitMask<<shift)) | (bitAllocated<<shift);
 		if(noptr)
 			bits |= bitNoPointers<<shift;
-		if(runtime·singleproc) {
+		if(runtime·gomaxprocs == 1) {
 			*b = bits;
 			break;
 		} else {
@@ -2377,7 +2377,7 @@ runtime·markfreed(void *v, uintptr n)
 	for(;;) {
 		obits = *b;
 		bits = (obits & ~(bitMask<<shift)) | (bitBlockBoundary<<shift);
-		if(runtime·singleproc) {
+		if(runtime·gomaxprocs == 1) {
 			*b = bits;
 			break;
 		} else {
@@ -2497,7 +2497,7 @@ runtime·setblockspecial(void *v, bool s)
 			bits = obits | (bitSpecial<<shift);
 		else
 			bits = obits & ~(bitSpecial<<shift);
-		if(runtime·singleproc) {
+		if(runtime·gomaxprocs == 1) {
 			*b = bits;
 			break;
 		} else {

src/pkg/runtime/proc.c

@@ -61,7 +61,6 @@ enum { MaxGomaxprocs = 1<<8 };
 Sched	runtime·sched;
 int32	runtime·gomaxprocs;
 uint32	runtime·needextram;
-bool	runtime·singleproc;
 bool	runtime·iscgo;
 uint32	runtime·gcwaiting;
 M	runtime·m0;
@@ -2060,7 +2059,6 @@ procresize(int32 new)
 		p->status = Pidle;
 		pidleput(p);
 	}
-	runtime·singleproc = new == 1;
 	runtime·atomicstore((uint32*)&runtime·gomaxprocs, new);
 }
 

src/pkg/runtime/runtime.h

@@ -700,7 +700,6 @@ extern	M*	runtime·allm;
 extern	P**	runtime·allp;
 extern	int32	runtime·gomaxprocs;
 extern	uint32	runtime·needextram;
-extern	bool	runtime·singleproc;
 extern	uint32	runtime·panicking;
 extern	uint32	runtime·gcwaiting;		// gc is waiting to run
 extern	int8*	runtime·goos;