From: Dmitriy Vyukov <dvyukov@google.com>
Date: Thu, 3 Jul 2014 18:58:42 +0000 (+0400)
Subject: runtime: delete unnecessary confusing code
X-Git-Tag: go1.4beta1~1168
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=d3be3daafef4b614fc676c807956047976848c7e;p=gostls13.git

runtime: delete unnecessary confusing code
The code in GC that handles gp->gobuf.ctxt is wrong,
because it does not mark the ctxt object itself,
if just queues the ctxt object for scanning.
So the ctxt object can be collected as garbage.
However, Gobuf.ctxt is void*, so it's always marked and
scanned through G.

LGTM=khr
R=golang-codereviews, khr
CC=golang-codereviews, khr, rsc
https://golang.org/cl/105490044
---

diff --git a/src/pkg/runtime/mgc0.c b/src/pkg/runtime/mgc0.c
index 4ad8f3b08f..059417209d 100644
--- a/src/pkg/runtime/mgc0.c
+++ b/src/pkg/runtime/mgc0.c
@@ -1615,8 +1615,6 @@ addstackroots(G *gp, Workbuf **wbufp)
 	int32 n;
 	Stktop *stk;
 	uintptr sp, guard;
-	void *base;
-	uintptr size;
 
 	switch(gp->status){
 	default:
@@ -1652,9 +1650,6 @@ addstackroots(G *gp, Workbuf **wbufp)
 		sp = gp->sched.sp;
 		stk = (Stktop*)gp->stackbase;
 		guard = gp->stackguard;
-		// For function about to start, context argument is a root too.
-		if(gp->sched.ctxt != 0 && runtime·mlookup(gp->sched.ctxt, &base, &size, nil))
-			enqueue1(wbufp, (Obj){base, size, 0});
 	}
 	if(ScanStackByFrames) {
 		USED(sp);
diff --git a/src/pkg/runtime/runtime.h b/src/pkg/runtime/runtime.h
index 0f630abbf2..2fab69b3a2 100644
--- a/src/pkg/runtime/runtime.h
+++ b/src/pkg/runtime/runtime.h
@@ -213,7 +213,7 @@ struct	Gobuf
 	uintptr	sp;
 	uintptr	pc;
 	G*	g;
-	void*	ctxt;
+	void*	ctxt; // this has to be a pointer so that GC scans it
 	uintreg	ret;
 	uintptr	lr;
 };