1. Avoid potential dead lock due to lock-order-inversion

runtime/vm/heap.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/heap.h"
 
 #include "platform/assert.h"
 #include "platform/utils.h"
 #include "vm/flags.h"
 #include "vm/isolate.h"
@@ skipping 69 matching lines @@
 uword Heap::AllocateOld(intptr_t size, HeapPage::PageType type) {
   ASSERT(Thread::Current()->no_safepoint_scope_depth() == 0);
   uword addr = old_space_.TryAllocate(size, type);
   if (addr != 0) {
     return addr;
   }
   // If we are in the process of running a sweep, wait for the sweeper to free
   // memory.
   Thread* thread = Thread::Current();
   if (thread->CanCollectGarbage()) {
-    {
-      MonitorLocker ml(old_space_.tasks_lock());
-      addr = old_space_.TryAllocate(size, type);
-      while ((addr == 0) && (old_space_.tasks() > 0)) {
-        ml.WaitWithSafepointCheck(thread);
-        addr = old_space_.TryAllocate(size, type);
-      }
-    }
+    // Wait for any GC tasks that are in progress.
+    WaitForSweeperTasks(thread);
+    addr = old_space_.TryAllocate(size, type);
     if (addr != 0) {
       return addr;
     }
     // All GC tasks finished without allocating successfully. Run a full GC.
     CollectAllGarbage();
     addr = old_space_.TryAllocate(size, type);
     if (addr != 0) {
       return addr;
     }
     // Wait for all of the concurrent tasks to finish before giving up.
-    {
-      MonitorLocker ml(old_space_.tasks_lock());
-      addr = old_space_.TryAllocate(size, type);
-      while ((addr == 0) && (old_space_.tasks() > 0)) {
-        ml.WaitWithSafepointCheck(thread);
-        addr = old_space_.TryAllocate(size, type);
-      }
-    }
+    WaitForSweeperTasks(thread);
+    addr = old_space_.TryAllocate(size, type);
     if (addr != 0) {
       return addr;
     }
     // Force growth before attempting another synchronous GC.
     addr = old_space_.TryAllocate(size, type, PageSpace::kForceGrowth);
     if (addr != 0) {
       return addr;
     }
     // Before throwing an out-of-memory error try a synchronous GC.
     CollectAllGarbage();
-    {
-      MonitorLocker ml(old_space_.tasks_lock());
-      while (old_space_.tasks() > 0) {
-        ml.WaitWithSafepointCheck(thread);
-      }
-    }
+    WaitForSweeperTasks(thread);
   }
   addr = old_space_.TryAllocate(size, type, PageSpace::kForceGrowth);
   if (addr != 0) {
     return addr;
   }
   // Give up allocating this object.
   OS::PrintErr("Exhausted heap space, trying to allocate %" Pd " bytes.\n",
                size);
   return 0;
 }
@@ skipping 296 matching lines @@
 }
 
 
 void Heap::CollectAllGarbage() {
   Thread* thread = Thread::Current();
   CollectNewSpaceGarbage(thread, kInvokeApiCallbacks, kFull);
   CollectOldSpaceGarbage(thread, kInvokeApiCallbacks, kFull);
 }
 
 
-#if defined(DEBUG)
-void Heap::WaitForSweeperTasks() {
-  Thread* thread = Thread::Current();
-  {
-    MonitorLocker ml(old_space_.tasks_lock());
-    while (old_space_.tasks() > 0) {
-      ml.WaitWithSafepointCheck(thread);
-    }
+void Heap::WaitForSweeperTasks(Thread* thread) {
+  MonitorLocker ml(old_space_.tasks_lock());
+  while (old_space_.tasks() > 0) {
+    ml.WaitWithSafepointCheck(thread);
   }
 }
-#endif
 
 
 void Heap::UpdateGlobalMaxUsed() {
   ASSERT(isolate_ != NULL);
   // We are accessing the used in words count for both new and old space
   // without synchronizing. The value of this metric is approximate.
   isolate_->GetHeapGlobalUsedMaxMetric()->SetValue(
       (UsedInWords(Heap::kNew) * kWordSize) +
       (UsedInWords(Heap::kOld) * kWordSize));
 }
@@ skipping 374 matching lines @@
   Dart::vm_isolate()->heap()->WriteProtect(false);
 }
 
 
 WritableVMIsolateScope::~WritableVMIsolateScope() {
   ASSERT(Dart::vm_isolate()->heap()->UsedInWords(Heap::kNew) == 0);
   Dart::vm_isolate()->heap()->WriteProtect(true);
 }
 
 }  // namespace dart