runtime: do not shrink stacks GOCOPYSTACK=0

LGTM=rsc
R=golang-codereviews
CC=golang-codereviews, khr, rsc
https://golang.org/cl/76070043

diff --git a/src/pkg/runtime/stack.c b/src/pkg/runtime/stack.c
index d580665e2bd3d61024b271cd5a6e3fa3b8474e9e..81005de5d7ba9f83f6cb35dd8f32b57b6f461bf6 100644 (file)
--- a/src/pkg/runtime/stack.c
+++ b/src/pkg/runtime/stack.c
@@ -776,6 +776,8 @@ runtime·shrinkstack(G *gp)
        uintptr used, oldsize, newsize;
        MSpan *span;
 
+       if(!runtime·copystack)
+               return;
        oldstk = (byte*)gp->stackguard - StackGuard;
        oldbase = (byte*)gp->stackbase + sizeof(Stktop);
        oldsize = oldbase - oldstk;