Thread fixes for shutdown.

runtime/vm/thread_pool.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/thread_pool.h"
 
 #include "vm/flags.h"
 #include "vm/lockers.h"
 
 namespace dart {
@@ skipping 89 matching lines @@
     MonitorLocker eml(&exit_monitor_);
 
     // First tell all the workers to shut down.
     Worker* current = saved;
     OSThread* os_thread = OSThread::Current();
     ASSERT(os_thread != NULL);
     ThreadId id = os_thread->id();
     while (current != NULL) {
       Worker* next = current->all_next_;
       ThreadId currentId = current->id();
-      if (currentId != id) {
+      if (currentId == OSThread::kInvalidThreadId) {
+        // If the thread id is invalid, it means the thread never started
+        // because OSThread creation was disabled. Destroy the Task and Worker.
+        delete current->task_;
+        delete current;
+        current = NULL;
+      } else if (currentId != id) {
         AddWorkerToShutdownList(current);
       }
-      current->Shutdown();
+      if (current != NULL) {
+        current->Shutdown();

[siva, 2015/12/30 20:51:02]

Why is it necessary to call current->Shutdown() when (currentId == id)?

[zra, 2015/12/30 22:36:28]

Thinking about this more, it is not safe for a thread-pool thread to call
ThreadPool::Shutdown(), so I've added an assert for that.

+      }
       current = next;
     }
     saved = NULL;
 
     // Wait until all workers will exit.
     while (shutting_down_workers_ != NULL) {
       // Here, we are waiting for workers to exit. When a worker exits we will
       // be notified.
       eml.Wait();
     }
@@ skipping 126 matching lines @@
   OSThread* os_thread = OSThread::Current();
   ASSERT(os_thread != NULL);
   JoinList::AddLocked(os_thread->join_id(), &join_list_);
   count_stopped_++;
   count_idle_--;
   return true;
 }
 
 
 // Only call while holding the exit_monitor_
 void ThreadPool::AddWorkerToShutdownList(Worker* worker) {

[siva, 2015/12/30 20:51:02]

ASSERT that the exit_monitor lock is held by the current thread?

[zra, 2015/12/30 22:36:28]

Done.

   worker->shutdown_next_ = shutting_down_workers_;
   shutting_down_workers_ = worker;
 }
 
 
 // Only call while holding the exit_monitor_
 bool ThreadPool::RemoveWorkerFromShutdownList(Worker* worker) {
   ASSERT(worker != NULL);
   ASSERT(shutting_down_workers_ != NULL);

[siva, 2015/12/30 20:51:02]

ASSERT that the exit_monitor lock is held by the current thread?

[zra, 2015/12/30 22:36:28]

Done.

 
   // Special case head of list.
   if (shutting_down_workers_ == worker) {
     shutting_down_workers_ = worker->shutdown_next_;
     worker->shutdown_next_ = NULL;
     return true;
   }
 
   for (Worker* current = shutting_down_workers_;
        current->shutdown_next_ != NULL;
@@ skipping 194 matching lines @@
     // is not due to a ThreadPool Shutdown. Thus, we simply delete the worker.
     // The worker's id is added to the thread pool's join list by
     // ReleaseIdleWorker, so in the case that the thread pool begins shutting
     // down immediately after returning from worker->Loop() above, we still
     // wait for the thread to exit by joining on it in Shutdown().
     delete worker;
   }
 }
 
 }  // namespace dart