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// 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 {
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 =
static_cast<AllocationContextTracker*>(g_tls_alloc_ctx_tracker.Get());
if (!tracker) {
tracker = new AllocationContextTracker();
g_tls_alloc_ctx_tracker.Set(tracker);
}
return tracker;
}
// 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);
}
// 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())
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())
<< "Encountered an unmatched TRACE_EVENT_END";
tracker->pseudo_stack_.pop_back();
}
// static
AllocationContext AllocationContextTracker::GetContextSnapshot() {
AllocationContextTracker* tracker = GetThreadLocalTracker();
AllocationContext ctx;
// Fill the backtrace.
{
auto src = tracker->pseudo_stack_.begin();
auto dst = std::begin(ctx.backtrace.frames);
auto src_end = tracker->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_id = 0;
return ctx;
}
} // namespace trace_event
} // namespace base
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