Fix for issue 27380 - VM stuck in deadlock with background finalization and background compiler thr…

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/compiler_stats.h"
 #include "vm/dart_api_state.h"
 #include "vm/growable_array.h"
 #include "vm/isolate.h"
@@ skipping 535 matching lines @@
   store_buffer_block_ = isolate()->store_buffer()->PopNonFullBlock();
 }
 
 
 bool Thread::IsMutatorThread() const {
   return ((isolate_ != NULL) && (isolate_->mutator_thread() == this));
 }
 
 
 bool Thread::CanCollectGarbage() const {
-  // We have non mutator threads grow the heap instead of triggering
-  // a garbage collection when they are at a safepoint (e.g: background
-  // compiler thread finalizing and installing code at a safepoint).
-  return (IsMutatorThread() || IsAtSafepoint());
+  // We grow the heap instead of triggering a garbage collection when a
+  // thread is at a safepoint in the following situations :
+  //   - background compiler thread finalizing and installing code
+  //   - disassembly of the generated code is done after compilation
+  // So essentially we state that garbage collection is possible only
+  // when we are not at a safepoint.
+  return !IsAtSafepoint();
 }
 
 
 bool Thread::IsExecutingDartCode() const {
   return (top_exit_frame_info() == 0) &&
          (vm_tag() == VMTag::kDartTagId);
 }
 
 
 bool Thread::HasExitedDartCode() const {
@@ skipping 185 matching lines @@
 
 DisableThreadInterruptsScope::~DisableThreadInterruptsScope() {
   if (thread() != NULL) {
     OSThread* os_thread = thread()->os_thread();
     ASSERT(os_thread != NULL);
     os_thread->EnableThreadInterrupts();
   }
 }
 
 }  // namespace dart