From 7bc42a145a03d61b504b18d20f2a4e5d8e2436fd Mon Sep 17 00:00:00 2001
From: Austin Clements <austin@google.com>
Date: Mon, 12 Sep 2016 17:48:34 -0400
Subject: [PATCH] runtime: don't reserve space for stack barriers if they're
 off

Change-Id: I79ebccdaefc434c47b77bd545cc3c50723c18b61
Reviewed-on: https://go-review.googlesource.com/31135
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
---
 src/runtime/mstkbar.go | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/runtime/mstkbar.go b/src/runtime/mstkbar.go
index 1bf9d573b7..4415559b6c 100644
--- a/src/runtime/mstkbar.go
+++ b/src/runtime/mstkbar.go
@@ -148,6 +148,10 @@ var firstStackBarrierOffset = 1024
 // gcMaxStackBarriers returns the maximum number of stack barriers
 // that can be installed in a stack of stackSize bytes.
 func gcMaxStackBarriers(stackSize int) (n int) {
+	if debug.gcstackbarrieroff > 0 {
+		return 0
+	}
+
 	if firstStackBarrierOffset == 0 {
 		// Special debugging case for inserting stack barriers
 		// at every frame. Steal half of the stack for the