runtime: address comments from CL 32357

Change-Id: I174d7307bfdd8ec57bb4266dab8569fd2234abb4
Reviewed-on: https://go-review.googlesource.com/32610Reviewed-by: Austin Clements <austin@google.com>
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/runtime/proc.go

@@ -475,7 +475,7 @@ func schedinit() {
 	goargs()
 	goenvs()
 	parsedebugvars()
-	gcinit() // requires modulesinit
+	gcinit()
 
 	sched.lastpoll = uint64(nanotime())
 	procs := ncpu

src/runtime/symtab.go

@@ -267,13 +267,10 @@ func activeModules() []*moduledata {
 //
 // Only one goroutine may call modulesinit at a time.
 func modulesinit() {
-	oldNum := len(activeModules())
 	modules := new([]*moduledata)
-	num := 0
 	for md := &firstmoduledata; md != nil; md = md.next {
 		*modules = append(*modules, md)
-		num++
-		if num > oldNum {
+		if md.gcdatamask == (bitvector{}) {
 			md.gcdatamask = progToPointerMask((*byte)(unsafe.Pointer(md.gcdata)), md.edata-md.data)
 			md.gcbssmask = progToPointerMask((*byte)(unsafe.Pointer(md.gcbss)), md.ebss-md.bss)
 		}