Make TimelineEventBlocks reclaimable

runtime/vm/thread.h

 // 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.
 
 #ifndef VM_THREAD_H_
 #define VM_THREAD_H_
 
 #include "vm/globals.h"
 #include "vm/os_thread.h"
 #include "vm/store_buffer.h"
@@ skipping 243 matching lines @@
   static intptr_t name##_entry_point_offset() {                                \
     return OFFSET_OF(Thread, name##_entry_point_);                             \
   }
 LEAF_RUNTIME_ENTRY_LIST(DEFINE_OFFSET_METHOD)
 #undef DEFINE_OFFSET_METHOD
 
   static bool CanLoadFromThread(const Object& object);
   static intptr_t OffsetFromThread(const Object& object);
   static intptr_t OffsetFromThread(const RuntimeEntry* runtime_entry);
 
+  Mutex* timeline_block_lock() {
+    return &timeline_block_lock_;
+  }
+
+  // Only safe to access when holding |timeline_block_lock_|.
   TimelineEventBlock* timeline_block() const {
     return state_.timeline_block;
   }
 
+  // Only safe to access when holding |timeline_block_lock_|.
   void set_timeline_block(TimelineEventBlock* block) {
     state_.timeline_block = block;
   }
 
   void CloseTimelineBlock();
   class Log* log() const;
 
   LongJumpScope* long_jump_base() const { return state_.long_jump_base; }
   void set_long_jump_base(LongJumpScope* value) {
     state_.long_jump_base = value;
@@ skipping 11 matching lines @@
 
  private:
   static ThreadLocalKey thread_key_;
 
   const ThreadId id_;
   ThreadInterruptCallback thread_interrupt_callback_;
   void* thread_interrupt_data_;
   Isolate* isolate_;
   Heap* heap_;
   State state_;
+  Mutex timeline_block_lock_;
   StoreBufferBlock* store_buffer_block_;
   class Log* log_;
 #define DECLARE_MEMBERS(type_name, member_name, expr, default_init_value)      \
   type_name member_name;
 CACHED_CONSTANTS_LIST(DECLARE_MEMBERS)
 #undef DECLARE_MEMBERS
 
 #define DECLARE_MEMBERS(name)      \
   uword name##_entry_point_;
 RUNTIME_ENTRY_LIST(DECLARE_MEMBERS)
@@ skipping 32 matching lines @@
   friend class ApiZone;
   friend class Isolate;
   friend class StackZone;
   friend class ThreadRegistry;
   DISALLOW_COPY_AND_ASSIGN(Thread);
 };
 
 }  // namespace dart
 
 #endif  // VM_THREAD_H_