alternate take on locking

Author: ktoso

stdlib/public/Concurrency/TaskGroup.cpp

@@ -1652,12 +1652,12 @@ static void swift_taskGroup_waitAllImpl(
     SwiftError *bodyError,
     ThrowingTaskFutureWaitContinuationFunction *resumeFunction,
     AsyncContext *rawContext) {
+  auto group = asBaseImpl(_group);
+  group->lock();
+
   auto waitingTask = swift_task_getCurrent();
   waitingTask->ResumeTask = task_group_wait_resume_adapter;
   waitingTask->ResumeContext = rawContext;
-
-  auto group = asBaseImpl(_group);
-  group->lock();
   PollResult polled = group->waitAll(bodyError, waitingTask);
 
   auto context = static_cast<TaskFutureWaitAsyncContext *>(rawContext);
@@ -1672,16 +1672,14 @@ static void swift_taskGroup_waitAllImpl(
 
   switch (polled.status) {
     case PollStatus::MustWait: {
-      group->unlock();
-
       // The waiting task has been queued on the channel,
       // there were pending tasks so it will be woken up eventually.
 #ifdef __ARM_ARCH_7K__
-      return workaround_function_swift_taskGroup_waitAllImpl(
+      workaround_function_swift_taskGroup_waitAllImpl(
          resultPointer, callerContext, _group, bodyError, resumeFunction, rawContext);
-#else /* __ARM_ARCH_7K__ */
-      return;
 #endif /* __ARM_ARCH_7K__ */
+      group->unlock();
+      return;
     }
 
     case PollStatus::Error: {