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// Copyright (c) 2012 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/metrics/histogram_snapshot_manager.h"
#include <memory>
#include "base/debug/alias.h"
#include "base/metrics/histogram_flattener.h"
#include "base/metrics/histogram_samples.h"
#include "base/metrics/statistics_recorder.h"
#include "base/stl_util.h"
namespace base {
namespace {
// A simple object to set an "active" flag and clear it upon destruction. It is
// an error if the flag is already set.
class MakeActive {
public:
MakeActive(std::atomic<bool>* is_active) : is_active_(is_active) {
bool was_active = is_active_->exchange(true, std::memory_order_relaxed);
CHECK(!was_active);
}
~MakeActive() { is_active_->store(false, std::memory_order_relaxed); }
private:
std::atomic<bool>* is_active_;
DISALLOW_COPY_AND_ASSIGN(MakeActive);
};
} // namespace
HistogramSnapshotManager::HistogramSnapshotManager(
HistogramFlattener* histogram_flattener)
: histogram_flattener_(histogram_flattener) {
DCHECK(histogram_flattener_);
is_active_.store(false, std::memory_order_relaxed);
}
HistogramSnapshotManager::~HistogramSnapshotManager() {
}
void HistogramSnapshotManager::PrepareDelta(HistogramBase* histogram) {
PrepareSamples(histogram, histogram->SnapshotDelta());
}
void HistogramSnapshotManager::PrepareFinalDelta(
const HistogramBase* histogram) {
PrepareSamples(histogram, histogram->SnapshotFinalDelta());
}
void HistogramSnapshotManager::PrepareSamples(
const HistogramBase* histogram,
std::unique_ptr<HistogramSamples> samples) {
DCHECK(histogram_flattener_);
// Ensure that there is no concurrent access going on while accessing the
// set of known histograms. The flag will be reset when this object goes
// out of scope.
MakeActive make_active(&is_active_);
// Get information known about this histogram. If it did not previously
// exist, one will be created and initialized.
SampleInfo* sample_info = &known_histograms_[histogram->name_hash()];
// Crash if we detect that our histograms have been overwritten. This may be
// a fair distance from the memory smasher, but we hope to correlate these
// crashes with other events, such as plugins, or usage patterns, etc.
uint32_t corruption = histogram->FindCorruption(*samples);
if (HistogramBase::BUCKET_ORDER_ERROR & corruption) {
// Extract fields useful during debug.
const BucketRanges* ranges =
static_cast<const Histogram*>(histogram)->bucket_ranges();
std::vector<HistogramBase::Sample> ranges_copy;
for (size_t i = 0; i < ranges->size(); ++i)
ranges_copy.push_back(ranges->range(i));
HistogramBase::Sample* ranges_ptr = &ranges_copy[0];
uint32_t ranges_checksum = ranges->checksum();
uint32_t ranges_calc_checksum = ranges->CalculateChecksum();
const char* histogram_name = histogram->histogram_name().c_str();
int32_t flags = histogram->flags();
// The checksum should have caught this, so crash separately if it didn't.
CHECK_NE(0U, HistogramBase::RANGE_CHECKSUM_ERROR & corruption);
CHECK(false); // Crash for the bucket order corruption.
// Ensure that compiler keeps around pointers to |histogram| and its
// internal |bucket_ranges_| for any minidumps.
base::debug::Alias(&ranges_ptr);
base::debug::Alias(&ranges_checksum);
base::debug::Alias(&ranges_calc_checksum);
base::debug::Alias(&histogram_name);
base::debug::Alias(&flags);
}
// Checksum corruption might not have caused order corruption.
CHECK_EQ(0U, HistogramBase::RANGE_CHECKSUM_ERROR & corruption);
// Note, at this point corruption can only be COUNT_HIGH_ERROR or
// COUNT_LOW_ERROR and they never arise together, so we don't need to extract
// bits from corruption.
if (corruption) {
DLOG(ERROR) << "Histogram: \"" << histogram->histogram_name()
<< "\" has data corruption: " << corruption;
histogram_flattener_->InconsistencyDetected(
static_cast<HistogramBase::Inconsistency>(corruption));
// Don't record corrupt data to metrics services.
const uint32_t old_corruption = sample_info->inconsistencies;
if (old_corruption == (corruption | old_corruption))
return; // We've already seen this corruption for this histogram.
sample_info->inconsistencies |= corruption;
histogram_flattener_->UniqueInconsistencyDetected(
static_cast<HistogramBase::Inconsistency>(corruption));
return;
}
if (samples->TotalCount() > 0)
histogram_flattener_->RecordDelta(*histogram, *samples);
}
} // namespace base
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