diff --git a/src/runtime/mgc.go b/src/runtime/mgc.go
index 8efee74243..44ff5fb08b 100644
--- a/src/runtime/mgc.go
+++ b/src/runtime/mgc.go
@@ -1383,7 +1383,7 @@ func gcBgMarkWorker() {
 			default:
 				throw("gcBgMarkWorker: unexpected gcMarkWorkerMode")
 			case gcMarkWorkerDedicatedMode:
-				gcDrain(&pp.gcw, gcDrainUntilPreempt|gcDrainFlushBgCredit)
+				gcDrainMarkWorkerDedicated(&pp.gcw, true)
 				if gp.preempt {
 					// We were preempted. This is
 					// a useful signal to kick
@@ -1398,11 +1398,11 @@ func gcBgMarkWorker() {
 				}
 				// Go back to draining, this time
 				// without preemption.
-				gcDrain(&pp.gcw, gcDrainFlushBgCredit)
+				gcDrainMarkWorkerDedicated(&pp.gcw, false)
 			case gcMarkWorkerFractionalMode:
-				gcDrain(&pp.gcw, gcDrainFractional|gcDrainUntilPreempt|gcDrainFlushBgCredit)
+				gcDrainMarkWorkerFractional(&pp.gcw)
 			case gcMarkWorkerIdleMode:
-				gcDrain(&pp.gcw, gcDrainIdle|gcDrainUntilPreempt|gcDrainFlushBgCredit)
+				gcDrainMarkWorkerIdle(&pp.gcw)
 			}
 			casgstatus(gp, _Gwaiting, _Grunning)
 		})
diff --git a/src/runtime/mgcmark.go b/src/runtime/mgcmark.go
index 2b4e23823b..9ab3b48f2f 100644
--- a/src/runtime/mgcmark.go
+++ b/src/runtime/mgcmark.go
@@ -1011,6 +1011,28 @@ const (
 	gcDrainFractional
 )
 
+// gcDrainMarkWorkerIdle is a wrapper for gcDrain that exists to better account
+// mark time in profiles.
+func gcDrainMarkWorkerIdle(gcw *gcWork) {
+	gcDrain(gcw, gcDrainIdle|gcDrainUntilPreempt|gcDrainFlushBgCredit)
+}
+
+// gcDrainMarkWorkerDedicated is a wrapper for gcDrain that exists to better account
+// mark time in profiles.
+func gcDrainMarkWorkerDedicated(gcw *gcWork, untilPreempt bool) {
+	flags := gcDrainFlushBgCredit
+	if untilPreempt {
+		flags |= gcDrainUntilPreempt
+	}
+	gcDrain(gcw, flags)
+}
+
+// gcDrainMarkWorkerFractional is a wrapper for gcDrain that exists to better account
+// mark time in profiles.
+func gcDrainMarkWorkerFractional(gcw *gcWork) {
+	gcDrain(gcw, gcDrainFractional|gcDrainUntilPreempt|gcDrainFlushBgCredit)
+}
+
 // gcDrain scans roots and objects in work buffers, blackening grey
 // objects until it is unable to get more work. It may return before
 // GC is done; it's the caller's responsibility to balance work from
@@ -1032,6 +1054,14 @@ const (
 //
 // gcDrain will always return if there is a pending STW.
 //
+// Disabling write barriers is necessary to ensure that after we've
+// confirmed that we've drained gcw, that we don't accidentally end
+// up flipping that condition by immediately adding work in the form
+// of a write barrier buffer flush.
+//
+// Don't set nowritebarrierrec because it's safe for some callees to
+// have write barriers enabled.
+//
 //go:nowritebarrier
 func gcDrain(gcw *gcWork, flags gcDrainFlags) {
 	if !writeBarrier.needed {