diff --git a/src/runtime/mgcmark.go b/src/runtime/mgcmark.go
index f6452ea133..bdb5888a28 100644
--- a/src/runtime/mgcmark.go
+++ b/src/runtime/mgcmark.go
@@ -366,9 +366,6 @@ func gcDrain(gcw *gcWork) {
 }
 
 // gcDrainN scans n objects, blackening grey objects.
-//
-// This MUST be run on the system stack to prevent a stop-the-world
-// while this locally holds GC work buffers.
 //go:nowritebarrier
 func gcDrainN(gcw *gcWork, n int) {
 	checknocurrentwbuf()
diff --git a/src/runtime/mgcwork.go b/src/runtime/mgcwork.go
index ecf603a739..f69d6bb6a1 100644
--- a/src/runtime/mgcwork.go
+++ b/src/runtime/mgcwork.go
@@ -41,8 +41,15 @@ func (wp wbufptr) ptr() *workbuf {
 // The usual pattern for using gcWork is:
 //
 //     var gcw gcWork
+//     disable preemption
 //     .. call gcw.put() to produce and gcw.get() to consume ..
 //     gcw.dispose()
+//     enable preemption
+//
+// It's important that any use of gcWork during the mark phase prevent
+// the garbage collector from transitioning to mark termination since
+// gcWork may locally hold GC work buffers. This can be done by
+// disabling preemption (systemstack or acquirem).
 type gcWork struct {
 	// Invariant: wbuf is never full or empty
 	wbuf wbufptr