Reland: add dump provider for malloc heap profiler (https://codereview.chromium.org/1675183006/)

base/trace_event/heap_profiler_allocation_context_tracker.cc

 // 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.
 
 #include "base/trace_event/heap_profiler_allocation_context_tracker.h"
 
 #include <algorithm>
 #include <iterator>
 
 #include "base/atomicops.h"
 #include "base/threading/thread_local_storage.h"
 #include "base/trace_event/heap_profiler_allocation_context.h"
 
 namespace base {
 namespace trace_event {
 
 subtle::Atomic32 AllocationContextTracker::capture_enabled_ = 0;
 
 namespace {
 
+const size_t kMaxStackDepth = 128u;
+AllocationContextTracker* const kInitializingSentinel =
+    reinterpret_cast<AllocationContextTracker*>(-1);
+
 ThreadLocalStorage::StaticSlot g_tls_alloc_ctx_tracker = TLS_INITIALIZER;
 
 // This function is added to the TLS slot to clean up the instance when the
 // thread exits.
 void DestructAllocationContextTracker(void* alloc_ctx_tracker) {
   delete static_cast<AllocationContextTracker*>(alloc_ctx_tracker);
 }
 
 }  // namespace
 
-AllocationContextTracker::AllocationContextTracker() {}
-AllocationContextTracker::~AllocationContextTracker() {}
-
 // static
-AllocationContextTracker* AllocationContextTracker::GetThreadLocalTracker() {
-  auto tracker =
+AllocationContextTracker*
+AllocationContextTracker::GetInstanceForCurrentThread() {
+  AllocationContextTracker* tracker =
       static_cast<AllocationContextTracker*>(g_tls_alloc_ctx_tracker.Get());
+  if (tracker == kInitializingSentinel)
+    return nullptr;  // Re-entrancy case.
 
   if (!tracker) {
+    g_tls_alloc_ctx_tracker.Set(kInitializingSentinel);
     tracker = new AllocationContextTracker();
     g_tls_alloc_ctx_tracker.Set(tracker);
   }
 
   return tracker;
 }
 
+AllocationContextTracker::AllocationContextTracker() {
+  pseudo_stack_.reserve(kMaxStackDepth);
+}
+AllocationContextTracker::~AllocationContextTracker() {}
+
 // static
 void AllocationContextTracker::SetCaptureEnabled(bool enabled) {
   // When enabling capturing, also initialize the TLS slot. This does not create
   // a TLS instance yet.
   if (enabled && !g_tls_alloc_ctx_tracker.initialized())
     g_tls_alloc_ctx_tracker.Initialize(DestructAllocationContextTracker);
 
   // Release ordering ensures that when a thread observes |capture_enabled_| to
   // be true through an acquire load, the TLS slot has been initialized.
   subtle::Release_Store(&capture_enabled_, enabled);
 }
 
-// static
 void AllocationContextTracker::PushPseudoStackFrame(StackFrame frame) {
-  auto tracker = AllocationContextTracker::GetThreadLocalTracker();
-
   // Impose a limit on the height to verify that every push is popped, because
   // in practice the pseudo stack never grows higher than ~20 frames.
-  DCHECK_LT(tracker->pseudo_stack_.size(), 128u);
-  tracker->pseudo_stack_.push_back(frame);
+  if (pseudo_stack_.size() < kMaxStackDepth)
+    pseudo_stack_.push_back(frame);
+  else
+    NOTREACHED();
 }
 
 // static
 void AllocationContextTracker::PopPseudoStackFrame(StackFrame frame) {
-  auto tracker = AllocationContextTracker::GetThreadLocalTracker();
-
   // Guard for stack underflow. If tracing was started with a TRACE_EVENT in
   // scope, the frame was never pushed, so it is possible that pop is called
   // on an empty stack.
-  if (tracker->pseudo_stack_.empty())
+  if (pseudo_stack_.empty())
     return;
 
   // Assert that pushes and pops are nested correctly. This DCHECK can be
   // hit if some TRACE_EVENT macro is unbalanced (a TRACE_EVENT_END* call
   // without a corresponding TRACE_EVENT_BEGIN).
-  DCHECK_EQ(frame, tracker->pseudo_stack_.back())
+  DCHECK_EQ(frame, pseudo_stack_.back())
       << "Encountered an unmatched TRACE_EVENT_END";
 
-  tracker->pseudo_stack_.pop_back();
+  pseudo_stack_.pop_back();
 }
 
 // static
 AllocationContext AllocationContextTracker::GetContextSnapshot() {
-  AllocationContextTracker* tracker = GetThreadLocalTracker();
   AllocationContext ctx;
 
   // Fill the backtrace.
   {
-    auto src = tracker->pseudo_stack_.begin();
+    auto src = pseudo_stack_.begin();
     auto dst = std::begin(ctx.backtrace.frames);
-    auto src_end = tracker->pseudo_stack_.end();
+    auto src_end = pseudo_stack_.end();
     auto dst_end = std::end(ctx.backtrace.frames);
 
     // Copy as much of the bottom of the pseudo stack into the backtrace as
     // possible.
     for (; src != src_end && dst != dst_end; src++, dst++)
       *dst = *src;
 
     // If there is room for more, fill the remaining slots with empty frames.
     std::fill(dst, dst_end, nullptr);
   }
 
   ctx.type_name = nullptr;
 
   return ctx;
 }
 
 }  // namespace trace_event
 }  // namespace base