setMaxPoolSize improvements

lib/pure/concurrency/threadpool.nim

@@ -134,7 +134,7 @@ proc await*(fv: FlowVarBase) =
 proc finished(fv: FlowVarBase) =
   doAssert fv.ai.isNil, "flowVar is still attached to an 'awaitAny'"
   # we have to protect against the rare cases where the owner of the flowVar
-  # simply disregards the flowVar and yet the "flowVarr" has not yet written
+  # simply disregards the flowVar and yet the "flowVar" has not yet written
   # anything to it:
   await(fv)
   if fv.data.isNil: return
@@ -207,6 +207,7 @@ proc `^`*[T](fv: FlowVar[T]): T =
   ## blocks until the value is available and then returns this value.
   await(fv)
   when T is string or T is seq:
+    # XXX closures? deepCopy?
     result = cast[T](fv.data)
   else:
     result = fv.blob
@@ -264,6 +265,10 @@ proc slave(w: ptr Worker) {.thread.} =
       w.shutdown = false
       atomicDec currentPoolSize
 
+var
+  workers: array[MaxThreadPoolSize, TThread[ptr Worker]]
+  workersData: array[MaxThreadPoolSize, Worker]
+
 proc setMinPoolSize*(size: range[1..MaxThreadPoolSize]) =
   ## sets the minimal thread pool size. The default value of this is 4.
   minPoolSize = size
@@ -272,10 +277,10 @@ proc setMaxPoolSize*(size: range[1..MaxThreadPoolSize]) =
   ## sets the minimal thread pool size. The default value of this
   ## is ``MaxThreadPoolSize``.
   maxPoolSize = size
-
-var
-  workers: array[MaxThreadPoolSize, TThread[ptr Worker]]
-  workersData: array[MaxThreadPoolSize, Worker]
+  if currentPoolSize > maxPoolSize:
+    for i in maxPoolSize..currentPoolSize-1:
+      let w = addr(workersData[i])
+      w.shutdown = true
 
 proc activateThread(i: int) {.noinline.} =
   workersData[i].taskArrived = createCondVar()