1// Copyright (c) 2012 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#include "base/metrics/histogram_snapshot_manager.h"
6
7#include <memory>
8
9#include "base/debug/alias.h"
10#include "base/metrics/histogram_flattener.h"
11#include "base/metrics/histogram_samples.h"
12#include "base/metrics/statistics_recorder.h"
13#include "base/stl_util.h"
14
15namespace base {
16
17HistogramSnapshotManager::HistogramSnapshotManager(
18    HistogramFlattener* histogram_flattener)
19    : histogram_flattener_(histogram_flattener) {
20  DCHECK(histogram_flattener_);
21}
22
23HistogramSnapshotManager::~HistogramSnapshotManager() {
24}
25
26void HistogramSnapshotManager::PrepareDelta(HistogramBase* histogram) {
27  PrepareSamples(histogram, histogram->SnapshotDelta());
28}
29
30void HistogramSnapshotManager::PrepareFinalDelta(
31    const HistogramBase* histogram) {
32  PrepareSamples(histogram, histogram->SnapshotFinalDelta());
33}
34
35void HistogramSnapshotManager::PrepareSamples(
36    const HistogramBase* histogram,
37    std::unique_ptr<HistogramSamples> samples) {
38  DCHECK(histogram_flattener_);
39
40  // Get information known about this histogram. If it did not previously
41  // exist, one will be created and initialized.
42  SampleInfo* sample_info = &known_histograms_[histogram->name_hash()];
43
44  // Crash if we detect that our histograms have been overwritten.  This may be
45  // a fair distance from the memory smasher, but we hope to correlate these
46  // crashes with other events, such as plugins, or usage patterns, etc.
47  uint32_t corruption = histogram->FindCorruption(*samples);
48  if (HistogramBase::BUCKET_ORDER_ERROR & corruption) {
49    // Extract fields useful during debug.
50    const BucketRanges* ranges =
51        static_cast<const Histogram*>(histogram)->bucket_ranges();
52    std::vector<HistogramBase::Sample> ranges_copy;
53    for (size_t i = 0; i < ranges->size(); ++i)
54      ranges_copy.push_back(ranges->range(i));
55    HistogramBase::Sample* ranges_ptr = &ranges_copy[0];
56    const char* histogram_name = histogram->histogram_name().c_str();
57    int32_t flags = histogram->flags();
58    // The checksum should have caught this, so crash separately if it didn't.
59    CHECK_NE(0U, HistogramBase::RANGE_CHECKSUM_ERROR & corruption);
60    CHECK(false);  // Crash for the bucket order corruption.
61    // Ensure that compiler keeps around pointers to |histogram| and its
62    // internal |bucket_ranges_| for any minidumps.
63    base::debug::Alias(&ranges_ptr);
64    base::debug::Alias(&histogram_name);
65    base::debug::Alias(&flags);
66  }
67  // Checksum corruption might not have caused order corruption.
68  CHECK_EQ(0U, HistogramBase::RANGE_CHECKSUM_ERROR & corruption);
69
70  // Note, at this point corruption can only be COUNT_HIGH_ERROR or
71  // COUNT_LOW_ERROR and they never arise together, so we don't need to extract
72  // bits from corruption.
73  if (corruption) {
74    DLOG(ERROR) << "Histogram: \"" << histogram->histogram_name()
75                << "\" has data corruption: " << corruption;
76    histogram_flattener_->InconsistencyDetected(
77        static_cast<HistogramBase::Inconsistency>(corruption));
78    // Don't record corrupt data to metrics services.
79    const uint32_t old_corruption = sample_info->inconsistencies;
80    if (old_corruption == (corruption | old_corruption))
81      return;  // We've already seen this corruption for this histogram.
82    sample_info->inconsistencies |= corruption;
83    histogram_flattener_->UniqueInconsistencyDetected(
84        static_cast<HistogramBase::Inconsistency>(corruption));
85    return;
86  }
87
88  if (samples->TotalCount() > 0)
89    histogram_flattener_->RecordDelta(*histogram, *samples);
90}
91
92void HistogramSnapshotManager::InspectLoggedSamplesInconsistency(
93      const HistogramSamples& new_snapshot,
94      HistogramSamples* logged_samples) {
95  HistogramBase::Count discrepancy =
96      logged_samples->TotalCount() - logged_samples->redundant_count();
97  if (!discrepancy)
98    return;
99
100  histogram_flattener_->InconsistencyDetectedInLoggedCount(discrepancy);
101  if (discrepancy > Histogram::kCommonRaceBasedCountMismatch) {
102    // Fix logged_samples.
103    logged_samples->Subtract(*logged_samples);
104    logged_samples->Add(new_snapshot);
105  }
106}
107
108}  // namespace base
109