Fixes for OSThread creation shutdown race.

runtime/vm/os_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/os_thread.h"
 
 #include "vm/atomic.h"
 #include "vm/lockers.h"
 #include "vm/log.h"
 #include "vm/thread_interrupter.h"
@@ skipping 18 matching lines @@
     timeline_block_(NULL),
     thread_list_next_(NULL),
     thread_interrupt_disabled_(1),  // Thread interrupts disabled by default.
     log_(new class Log()),
     stack_base_(0),
     thread_(NULL) {
 }
 
 
 OSThread* OSThread::CreateOSThread() {
-  if (thread_list_lock_ == NULL) {
+  MutexLocker ml(thread_list_lock_);
+  if (!creation_enabled_) {
     return NULL;
   }
-  {
-    MutexLocker ml(thread_list_lock_);
-    if (!creation_enabled_) {
-      return NULL;
-    }
-    OSThread* os_thread = new OSThread();
-    AddThreadToListLocked(os_thread);
-    return os_thread;
-  }
+  OSThread* os_thread = new OSThread();
+  AddThreadToListLocked(os_thread);
+  return os_thread;
 }
 
 
 OSThread::~OSThread() {
   RemoveThreadFromList(this);
   delete log_;
   log_ = NULL;
   if (Timeline::recorder() != NULL) {
     Timeline::recorder()->FinishBlock(timeline_block_);
   }
@@ skipping 53 matching lines @@
   // Create a new OSThread strcture and set it as the TLS.
   OSThread* os_thread = CreateOSThread();
   ASSERT(os_thread != NULL);
   OSThread::SetCurrent(os_thread);
   os_thread->set_name("Dart_Initialize");
 }
 
 
 void OSThread::Cleanup() {
   if (thread_list_lock_ != NULL) {
+    // We cannot delete the key, yet. See the note about thread_list_lock_.
     // Delete the thread local key.
-    ASSERT(thread_key_ != kUnsetThreadLocalKey);
-    DeleteThreadLocal(thread_key_);
-    thread_key_ = kUnsetThreadLocalKey;
+    // ASSERT(thread_key_ != kUnsetThreadLocalKey);
+    // DeleteThreadLocal(thread_key_);
+    // thread_key_ = kUnsetThreadLocalKey;
 
+    // The thread_list_lock_ cannot be deleted without a bit more cleverness.
+    // See the note in os_thread.h.
     // Delete the global OSThread lock.
-    ASSERT(thread_list_lock_ != NULL);
-    delete thread_list_lock_;
-    thread_list_lock_ = NULL;
+    // ASSERT(thread_list_lock_ != NULL);
+    // delete thread_list_lock_;
+    // thread_list_lock_ = NULL;
   }

[siva, 2016/01/04 23:07:55]

Since everything inside the 'if statement' is commented out why not put the
whole statement under #if 0....#endif

[zra, 2016/01/04 23:21:53]

Done.

 }
 
 
 OSThread* OSThread::CreateAndSetUnknownThread() {
   ASSERT(OSThread::GetCurrentTLS() == NULL);
   OSThread* os_thread = CreateOSThread();
   if (os_thread != NULL) {
     OSThread::SetCurrent(os_thread);
     os_thread->set_name("Unknown");
   }
@@ skipping 124 matching lines @@
 
 OSThread* OSThreadIterator::Next() {
   ASSERT(OSThread::thread_list_lock_ != NULL);
   ASSERT(OSThread::thread_list_lock_->IsOwnedByCurrentThread());
   OSThread* current = next_;
   next_ = next_->thread_list_next_;
   return current;
 }
 
 }  // namespace dart