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

runtime/vm/pages.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/pages.h"
 
 #include "platform/assert.h"
 #include "vm/compiler_stats.h"
 #include "vm/gc_marker.h"
 #include "vm/gc_sweeper.h"
@@ skipping 363 matching lines @@
 }
 
 
 uword PageSpace::TryAllocateInternal(intptr_t size,
                                      HeapPage::PageType type,
                                      GrowthPolicy growth_policy,
                                      bool is_protected,
                                      bool is_locked) {
   ASSERT(size >= kObjectAlignment);
   ASSERT(Utils::IsAligned(size, kObjectAlignment));
-#ifdef DEBUG
-  SpaceUsage usage_before = GetCurrentUsage();
-#endif
   uword result = 0;
   if (size < kAllocatablePageSize) {
     if (is_locked) {
       result = freelist_[type].TryAllocateLocked(size, is_protected);
     } else {
       result = freelist_[type].TryAllocate(size, is_protected);
     }
     if (result == 0) {
       result = TryAllocateInFreshPage(size, type, growth_policy, is_locked);
       // usage_ is updated by the call above.
@@ skipping 16 matching lines @@
         CanIncreaseCapacityInWords(page_size_in_words)) {
       HeapPage* page = AllocateLargePage(size, type);
       if (page != NULL) {
         result = page->object_start();
         // Note: usage_.capacity_in_words is increased by AllocateLargePage.
         AtomicOperations::IncrementBy(&(usage_.used_in_words),
                                       (size >> kWordSizeLog2));
       }
     }
   }
-#ifdef DEBUG
-  if (result != 0) {
-    // A successful allocation should increase usage_.
-    ASSERT(usage_before.used_in_words < usage_.used_in_words);
-  }
-// Note we cannot assert that a failed allocation should not change
-// used_in_words as another thread could have changed used_in_words.
-#endif
   ASSERT((result & kObjectAlignmentMask) == kOldObjectAlignmentOffset);
   return result;
 }
 
 
 void PageSpace::AcquireDataLock() {
   freelist_[HeapPage::kData].mutex()->Lock();
 }
 
 
@@ skipping 828 matching lines @@
     return 0;
   } else {
     ASSERT(total_time >= gc_time);
     int result = static_cast<int>(
         (static_cast<double>(gc_time) / static_cast<double>(total_time)) * 100);
     return result;
   }
 }
 
 }  // namespace dart