[dev.inline] merge with master at 894d24d617dev.inline

Change-Id: I845eec08108c69228ebcba921f8a807a376d3fae

1 files changed, 12 insertions, 1 deletions

diff --git a/src/runtime/mstats.go b/src/runtime/mstats.go
index ab383dd8e3..9cdc565137 100644
--- a/src/runtime/mstats.go
+++ b/src/runtime/mstats.go
@@ -199,7 +199,17 @@ type MemStats struct {
 	// StackSys is bytes of stack memory obtained from the OS.
 	//
 	// StackSys is StackInuse, plus any memory obtained directly
-	// from the OS for OS thread stacks (which should be minimal).
+	// from the OS for OS thread stacks.
+	//
+	// In non-cgo programs this metric is currently equal to StackInuse
+	// (but this should not be relied upon, and the value may change in
+	// the future).
+	//
+	// In cgo programs this metric includes OS thread stacks allocated
+	// directly from the OS. Currently, this only accounts for one stack in
+	// c-shared and c-archive build modes and other sources of stacks from
+	// the OS (notably, any allocated by C code) are not currently measured.
+	// Note this too may change in the future.
 	StackSys uint64
 
 	// Off-heap memory statistics.
@@ -347,6 +357,7 @@ func init() {
 // which is a snapshot as of the most recently completed garbage
 // collection cycle.
 func ReadMemStats(m *MemStats) {
+	_ = m.Alloc // nil check test before we switch stacks, see issue 61158
 	stopTheWorld(stwReadMemStats)
 
 	systemstack(func() {