runtime: convert clearpools/registerPoolCleanup to Go

LGTM=bradfitz, rsc
R=golang-codereviews, bradfitz, rsc
CC=golang-codereviews, khr
https://golang.org/cl/133240043

src/pkg/runtime/mgc0.c

@@ -82,39 +82,6 @@ enum {
 // Initialized from $GOGC.  GOGC=off means no gc.
 extern int32 runtime·gcpercent;
 
-static FuncVal* poolcleanup;
-
-void
-sync·runtime_registerPoolCleanup(FuncVal *f)
-{
-	poolcleanup = f;
-}
-
-void
-runtime·clearpools(void)
-{
-	P *p, **pp;
-	MCache *c;
-	int32 i;
-
-	// clear sync.Pool's
-	if(poolcleanup != nil)
-		reflect·call(poolcleanup, nil, 0, 0);
-
-	for(pp=runtime·allp; p=*pp; pp++) {
-		// clear tinyalloc pool
-		c = p->mcache;
-		if(c != nil) {
-			c->tiny = nil;
-			c->tinysize = 0;
-			c->sudogcache = nil;
-		}
-		// clear defer pools
-		for(i=0; i<nelem(p->deferpool); i++)
-			p->deferpool[i] = nil;
-	}
-}
-
 // Holding worldsema grants an M the right to try to stop the world.
 // The procedure is:
 //

src/pkg/runtime/mgc0.go

@@ -39,3 +39,32 @@ func freeOSMemory() {
 	gogc(2) // force GC and do eager sweep
 	onM(&scavenge_m)
 }
+
+var poolcleanup func()
+
+func registerPoolCleanup(f func()) {
+	poolcleanup = f
+}
+
+func clearpools() {
+	// clear sync.Pools
+	if poolcleanup != nil {
+		poolcleanup()
+	}
+
+	for _, p := range &allp {
+		if p == nil {
+			break
+		}
+		// clear tinyalloc pool
+		if c := p.mcache; c != nil {
+			c.tiny = nil
+			c.tinysize = 0
+			c.sudogcache = nil
+		}
+		// clear defer pools
+		for i := range p.deferpool {
+			p.deferpool[i] = nil
+		}
+	}
+}

src/pkg/runtime/stubs.go

@@ -110,7 +110,6 @@ const (
 func gosched()
 func starttheworld()
 func stoptheworld()
-func clearpools()
 
 // exported value for testing
 var hashLoad = loadFactor

src/pkg/runtime/thunk.s

@@ -38,6 +38,9 @@ TEXT sync·runtime_Semacquire(SB),NOSPLIT,$0-0
 TEXT sync·runtime_Semrelease(SB),NOSPLIT,$0-0
 	JMP	runtime·asyncsemrelease(SB)
 
+TEXT sync·runtime_registerPoolCleanup(SB),NOSPLIT,$0-0
+	JMP	runtime·registerPoolCleanup(SB)
+
 TEXT net·runtime_Semacquire(SB),NOSPLIT,$0-0
 	JMP	runtime·asyncsemacquire(SB)