Don't cleanup thread list mutex until VM shutdown is clean

runtime/vm/thread.cc

 // Copyright (c) 2015, 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.h"
 
 #include "vm/growable_array.h"
 #include "vm/isolate.h"
 #include "vm/lockers.h"
 #include "vm/log.h"
 #include "vm/native_entry.h"
 #include "vm/object.h"
 #include "vm/os_thread.h"
 #include "vm/profiler.h"
 #include "vm/runtime_entry.h"
 #include "vm/stub_code.h"
 #include "vm/symbols.h"
 #include "vm/thread_interrupter.h"
 #include "vm/thread_registry.h"
 
 namespace dart {
 
 // The single thread local key which stores all the thread local data
 // for a thread.
 ThreadLocalKey Thread::thread_key_ = OSThread::kUnsetThreadLocalKey;
 Thread* Thread::thread_list_head_ = NULL;
-Mutex* Thread::thread_list_lock_;
+Mutex* Thread::thread_list_lock_ = NULL;
 
 // Remove |thread| from each isolate's thread registry.
 class ThreadPruner : public IsolateVisitor {
  public:
   explicit ThreadPruner(Thread* thread)
       : thread_(thread) {
     ASSERT(thread_ != NULL);
   }
 
   void VisitIsolate(Isolate* isolate) {
     ThreadRegistry* registry = isolate->thread_registry();
     ASSERT(registry != NULL);
     registry->PruneThread(thread_);
   }
  private:
   Thread* thread_;
 };
 
 
 void Thread::AddThreadToList(Thread* thread) {
   ASSERT(thread != NULL);
   ASSERT(thread->isolate() == NULL);
+  ASSERT(thread_list_lock_ != NULL);
   MutexLocker ml(thread_list_lock_);
 
   ASSERT(thread->thread_list_next_ == NULL);
 
 #if defined(DEBUG)
   {
     // Ensure that we aren't already in the list.
     Thread* current = thread_list_head_;
     while (current != NULL) {
       ASSERT(current != thread);
       current = current->thread_list_next_;
     }
   }
 #endif
 
   // Insert at head of list.
   thread->thread_list_next_ = thread_list_head_;
   thread_list_head_ = thread;
 }
 
 
 void Thread::RemoveThreadFromList(Thread* thread) {
   ASSERT(thread != NULL);
   ASSERT(thread->isolate() == NULL);
+  ASSERT(thread_list_lock_ != NULL);
   MutexLocker ml(thread_list_lock_);
 
   // Handle case where |thread| is head of list.
   if (thread_list_head_ == thread) {
     thread_list_head_ = thread->thread_list_next_;
     thread->thread_list_next_ = NULL;
     return;
   }
 
   Thread* current = thread_list_head_;
@@ skipping 34 matching lines @@
   // Clear |this| from all isolate's thread registry.
   ThreadPruner pruner(this);
   Isolate::VisitIsolates(&pruner);
   delete log_;
   log_ = NULL;
   RemoveThreadFromList(this);
 }
 
 
 void Thread::InitOnceBeforeIsolate() {
+  ASSERT(thread_list_lock_ == NULL);
+  thread_list_lock_ = new Mutex();
+  ASSERT(thread_list_lock_ != NULL);
   ASSERT(thread_key_ == OSThread::kUnsetThreadLocalKey);
   thread_key_ = OSThread::CreateThreadLocal(DeleteThread);
   ASSERT(thread_key_ != OSThread::kUnsetThreadLocalKey);
   ASSERT(Thread::Current() == NULL);
-  thread_list_lock_ = new Mutex();
   // Allocate a new Thread and postpone initialization of VM constants for
   // this first thread.
   Thread* thread = new Thread(false);
   // Verify that current thread was set.
   ASSERT(Thread::Current() == thread);
 }
 
 
 void Thread::InitOnceAfterObjectAndStubCode() {
   Thread* thread = Thread::Current();
@@ skipping 383 matching lines @@
 Thread* ThreadIterator::Next() {
   ASSERT(Thread::thread_list_lock_ != NULL);
   ASSERT(Thread::thread_list_lock_->IsOwnedByCurrentThread());
   Thread* current = next_;
   next_ = next_->thread_list_next_;
   return current;
 }
 
 
 }  // namespace dart