tracing: add dump provider for malloc heap profiler

base/trace_event/heap_profiler_allocation_context_tracker.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_TRACE_EVENT_HEAP_PROFILER_ALLOCATION_CONTEXT_TRACKER_H_
 #define BASE_TRACE_EVENT_HEAP_PROFILER_ALLOCATION_CONTEXT_TRACKER_H_
 
 #include <vector>
 
 #include "base/atomicops.h"
 #include "base/base_export.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/trace_event/heap_profiler_allocation_context.h"
 
 namespace base {
 namespace trace_event {
 
 // The allocation context tracker keeps track of thread-local context for heap
 // profiling. It includes a pseudo stack of trace events. On every allocation
 // the tracker provides a snapshot of its context in the form of an
 // |AllocationContext| that is to be stored together with the allocation
 // details.
 class BASE_EXPORT AllocationContextTracker {
  public:
+  enum InitializationState { kNotInitialized = 0, kInitializing, kInitialized };
+
   // Globally enables capturing allocation context.
   // TODO(ruuda): Should this be replaced by |EnableCapturing| in the future?
   // Or at least have something that guards agains enable -> disable -> enable?
   static void SetCaptureEnabled(bool enabled);
 
+  // Exposes the initialization state of the tracker. This is to avoid
+  // re-entrancy in the malloc heap profiler, that will lazy initialize the

[petrcermak, 2016/03/11 11:09:23]

nit: s/that/which/ (you can't have "that" after a comma, which should stay here
in this case)

[petrcermak, 2016/03/11 11:09:23]

nit: s/lazy/lazily/

[Primiano Tucci (use gerrit), 2016/03/11 13:57:57]

Done.

[Primiano Tucci (use gerrit), 2016/03/11 13:57:57]

Done.

+  // thread-local context trackes on the first malloc seen, causing a nested

[petrcermak, 2016/03/11 11:09:23]

s/trackes/trackers/

[petrcermak, 2016/03/11 11:09:23]

supernit: wouldn't "first encountered malloc" read a little better?

[Primiano Tucci (use gerrit), 2016/03/11 13:57:57]

Done.

[Primiano Tucci (use gerrit), 2016/03/11 13:57:57]

actually was "tracker" , just typoed r/s

+  // allocation.
+  static InitializationState GetStateForCurrentThread();
+
+  // Enforces the initialization of the tracker. Subsequent calls to the other
+  // methods of this class are supposed to not cause any further malloc/new.
+  static AllocationContextTracker* InitializeForCurrentThread();
+
   // Returns whether capturing allocation context is enabled globally.
   inline static bool capture_enabled() {
     // A little lag after heap profiling is enabled or disabled is fine, it is
     // more important that the check is as cheap as possible when capturing is
     // not enabled, so do not issue a memory barrier in the fast path.
     if (subtle::NoBarrier_Load(&capture_enabled_) == 0)
       return false;
 
     // In the slow path, an acquire load is required to pair with the release
     // store in |SetCaptureEnabled|. This is to ensure that the TLS slot for
@@ skipping 23 matching lines @@
   // The pseudo stack where frames are |TRACE_EVENT| names.
   std::vector<StackFrame> pseudo_stack_;
 
   DISALLOW_COPY_AND_ASSIGN(AllocationContextTracker);
 };
 
 }  // namespace trace_event
 }  // namespace base
 
 #endif  // BASE_TRACE_EVENT_HEAP_PROFILER_ALLOCATION_CONTEXT_TRACKER_H_