runtime (gc): do not scan the runqueue when the platform is not baremetal with a scheduler

src/runtime/baremetal.go

@@ -38,3 +38,5 @@ func libc_malloc(size uintptr) unsafe.Pointer {
 func libc_free(ptr unsafe.Pointer) {
 	free(ptr)
 }
+
+const baremetal = true

src/runtime/gc_conservative.go

@@ -297,10 +297,11 @@ func GC() {
 	markStack()
 	markGlobals()
 
+	if baremetal && hasScheduler {
 		// Channel operations in interrupts may move task pointers around while we are marking.
 		// Therefore we need to scan the runqueue seperately.
 		var markedTaskQueue task.Queue
-runqueueScan:
+	runqueueScan:
 		for !runqueue.Empty() {
 			// Pop the next task off of the runqueue.
 			t := runqueue.Pop()
@@ -323,6 +324,9 @@ runqueueScan:
 		}
 		runqueue = markedTaskQueue
 		interrupt.Restore(i)
+	} else {
+		finishMark()
+	}
 
 	// Sweep phase: free all non-marked objects and unmark marked objects for
 	// the next collection cycle.

src/runtime/hosted.go

@@ -0,0 +1,5 @@
+// +build !baremetal
+
+package runtime
+
+const baremetal = false