bugfix

lib/system/seqs_v2.nim

@@ -27,8 +27,9 @@ when defined(gcYrc):
     lockState {.threadvar.}: YrcLockState
 
   proc acquireMutatorLock() {.compilerRtl, inl.} =
-    acquireRead gYrcGlobalLock
-    lockState = HasMutatorLock
+    if lockState == HasNoLock:
+      acquireRead gYrcGlobalLock
+      lockState = HasMutatorLock
 
   proc releaseMutatorLock() {.compilerRtl, inl.} =
     if lockState == HasMutatorLock:

lib/system/yrc.nim

@@ -435,7 +435,7 @@ when defined(nimOrcStats):
 proc GC_runOrc* =
   yrcCollectorLock:
     mergePendingRoots()
-    if mayRunCycleCollect():
+    if roots.len > 0 and mayRunCycleCollect():
       var j: GcEnv
       init j.traceStack
       collectCyclesBacon(j, 0)