runtime: fix panic if newstack at runtime.acquireLockRank

src/runtime/lockrank_off.go

@@ -18,19 +18,29 @@ func getLockRank(l *mutex) lockRank {
 	return 0
 }
 
+// The following functions may be called in nosplit context.
+// Nosplit is not strictly required for lockWithRank, unlockWithRank
+// and lockWithRankMayAcquire, but these nosplit annotations must
+// be kept consistent with the equivalent functions in lockrank_on.go.
+
+//go:nosplit
 func lockWithRank(l *mutex, rank lockRank) {
 	lock2(l)
 }
 
+//go:nosplit
 func acquireLockRank(rank lockRank) {
 }
 
+//go:nosplit
 func unlockWithRank(l *mutex) {
 	unlock2(l)
 }
 
+//go:nosplit
 func releaseLockRank(rank lockRank) {
 }
 
+//go:nosplit
 func lockWithRankMayAcquire(l *mutex, rank lockRank) {
 }