Fix for issue 25236

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"
 
 namespace dart {
 
 // The single thread local key which stores all the thread local data
 // for a thread.
 ThreadLocalKey OSThread::thread_key_ = kUnsetThreadLocalKey;
 OSThread* OSThread::thread_list_head_ = NULL;
 Mutex* OSThread::thread_list_lock_ = NULL;
+bool OSThread::creation_enabled_ = false;
 
 
 OSThread::OSThread() :
     BaseThread(true),
     id_(OSThread::GetCurrentThreadId()),
     join_id_(OSThread::GetCurrentThreadJoinId()),
     trace_id_(OSThread::GetCurrentThreadTraceId()),
     name_(NULL),
     timeline_block_lock_(new Mutex()),
     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) {
-  AddThreadToList(this);
 }
 
 
 OSThread::~OSThread() {
   RemoveThreadFromList(this);
   delete log_;
   log_ = NULL;
   if (Timeline::recorder() != NULL) {
     Timeline::recorder()->FinishBlock(timeline_block_);
   }
@@ skipping 29 matching lines @@
 bool OSThread::ThreadInterruptsEnabled() {
   return AtomicOperations::LoadRelaxed(&thread_interrupt_disabled_) == 0;
 }
 
 
 static void DeleteThread(void* thread) {
   delete reinterpret_cast<OSThread*>(thread);
 }
 
 
+OSThread* OSThread::CreateOSThread() {
+  ASSERT(thread_list_lock_ != NULL);
+  MutexLocker ml(thread_list_lock_);
+  if (!creation_enabled_) {
+    return NULL;
+  }
+  OSThread* os_thread = new OSThread();
+  AddThreadToList(os_thread);
+  return os_thread;
+}
+
+
 void OSThread::InitOnce() {
   // Allocate the global OSThread lock.
   ASSERT(thread_list_lock_ == NULL);
   thread_list_lock_ = new Mutex();
   ASSERT(thread_list_lock_ != NULL);
 
   // Create the thread local key.
   ASSERT(thread_key_ == kUnsetThreadLocalKey);
   thread_key_ = CreateThreadLocal(DeleteThread);
   ASSERT(thread_key_ != kUnsetThreadLocalKey);
 
+  // Enable creation of OSThread structures in the VM.
+  EnableOSThreadCreation();
+
   // Create a new OSThread strcture and set it as the TLS.
-  OSThread* os_thread = new OSThread();
+  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) {
     // Delete the thread local key.
     ASSERT(thread_key_ != kUnsetThreadLocalKey);
     DeleteThreadLocal(thread_key_);
     thread_key_ = kUnsetThreadLocalKey;
 
     // Delete the global OSThread lock.
     ASSERT(thread_list_lock_ != NULL);
     delete thread_list_lock_;
     thread_list_lock_ = NULL;
   }
 }
 
 
 OSThread* OSThread::CreateAndSetUnknownThread() {
   ASSERT(OSThread::Current() == NULL);
-  OSThread* os_thread = new OSThread();
-  OSThread::SetCurrent(os_thread);
-  os_thread->set_name("Unknown");
+  OSThread* os_thread = CreateOSThread();
+  if (os_thread != NULL) {
+    OSThread::SetCurrent(os_thread);
+    os_thread->set_name("Unknown");
+  }
   return os_thread;
 }
 
 
 bool OSThread::IsThreadInList(ThreadJoinId join_id) {
   if (join_id == OSThread::kInvalidThreadJoinId) {
     return false;
   }
   OSThreadIterator it;
   while (it.HasNext()) {
     ASSERT(OSThread::thread_list_lock_->IsOwnedByCurrentThread());
     OSThread* t = it.Next();
     // An address test is not sufficient because the allocator may recycle
     // the address for another Thread. Test against the thread's join id.
     if (t->join_id() == join_id) {
       return true;
     }
   }
   return false;
 }
 
 
+void OSThread::DisableOSThreadCreation() {

[zra, 2015/12/17 16:37:59]

Where is this called?

[siva, 2015/12/17 18:19:13]

Good point, forgot to add the call in Dart::Cleanup.

+  MutexLocker ml(thread_list_lock_);
+  creation_enabled_ = false;
+}
+
+
+void OSThread::EnableOSThreadCreation() {
+  MutexLocker ml(thread_list_lock_);
+  creation_enabled_ = true;
+}
+
+
 OSThread* OSThread::GetOSThreadFromThread(Thread* thread) {
   ASSERT(thread->os_thread() != NULL);
   return thread->os_thread();
 }
 
 
 void OSThread::AddThreadToList(OSThread* thread) {

[zra, 2015/12/17 16:37:59]

AddThreadToListLocked?

[siva, 2015/12/17 18:19:13]

Done.

   ASSERT(thread != NULL);
   ASSERT(thread_list_lock_ != NULL);
-  MutexLocker ml(thread_list_lock_);
-
+  ASSERT(OSThread::thread_list_lock_->IsOwnedByCurrentThread());
+  ASSERT(creation_enabled_);
   ASSERT(thread->thread_list_next_ == NULL);
 
 #if defined(DEBUG)
   {
     // Ensure that we aren't already in the list.
     OSThread* 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 OSThread::RemoveThreadFromList(OSThread* thread) {
+  bool final_thread = false;
   {
     ASSERT(thread != NULL);
     ASSERT(thread_list_lock_ != NULL);
     MutexLocker ml(thread_list_lock_);
     OSThread* current = thread_list_head_;
     OSThread* previous = NULL;
 
     // Scan across list and remove |thread|.
     while (current != NULL) {
       if (current == thread) {
         // We found |thread|, remove from list.
         if (previous == NULL) {
           thread_list_head_ = thread->thread_list_next_;
         } else {
           previous->thread_list_next_ = current->thread_list_next_;
         }
         thread->thread_list_next_ = NULL;
+        final_thread = !creation_enabled_  && (thread_list_head_ == NULL);

[Florian Schneider, 2015/12/17 13:33:08]

It seems DisableOSThreadCreation is never called in the shutdown procedure, so
as a result Cleanup would never be called below.

[siva, 2015/12/17 18:19:13]

Good catch, forgot to add the call in Dart::Cleanup.

         break;
       }
       previous = current;
       current = current->thread_list_next_;
     }
   }
   // Check if this is the last thread. The last thread does a cleanup
   // which removes the thread local key and the associated mutex.
-  if (thread_list_head_ == NULL) {
+  if (final_thread) {
     Cleanup();
   }
 }
 
 
 void OSThread::SetCurrent(OSThread* current) {
   OSThread::SetThreadLocal(thread_key_, reinterpret_cast<uword>(current));
 }
 
 
@@ skipping 21 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