From: Austin Clements <austin@google.com>
Date: Wed, 3 Apr 2019 20:32:42 +0000 (-0400)
Subject: runtime: note about improved _Gscan bit handling
X-Git-Tag: go1.13beta1~730
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=0188cb0e8a7a2355a0eebbf557fc444e5bfa30de;p=gostls13.git

runtime: note about improved _Gscan bit handling

Change-Id: I8de5aa64a24e77e0ef876918fcace7668769ebc2
Reviewed-on: https://go-review.googlesource.com/c/go/+/171022
Reviewed-by: Michael Knyszek <mknyszek@google.com>
---

diff --git a/src/runtime/runtime2.go b/src/runtime/runtime2.go
index cfea1cd45f..8d749f3d7c 100644
--- a/src/runtime/runtime2.go
+++ b/src/runtime/runtime2.go
@@ -22,6 +22,13 @@ const (
 	// If you add to this list, add to the list
 	// of "okay during garbage collection" status
 	// in mgcmark.go too.
+	//
+	// TODO(austin): The _Gscan bit could be much lighter-weight.
+	// For example, we could choose not to run _Gscanrunnable
+	// goroutines found in the run queue, rather than CAS-looping
+	// until they become _Grunnable. And transitions like
+	// _Gscanwaiting -> _Gscanrunnable are actually okay because
+	// they don't affect stack ownership.
 
 	// _Gidle means this goroutine was just allocated and has not
 	// yet been initialized.