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
15 namespace base {
16
HistogramSnapshotManager(HistogramFlattener * histogram_flattener)17 HistogramSnapshotManager::HistogramSnapshotManager(
18 HistogramFlattener* histogram_flattener)
19 : histogram_flattener_(histogram_flattener) {
20 DCHECK(histogram_flattener_);
21 }
22
~HistogramSnapshotManager()23 HistogramSnapshotManager::~HistogramSnapshotManager() {
24 }
25
PrepareDelta(HistogramBase * histogram)26 void HistogramSnapshotManager::PrepareDelta(HistogramBase* histogram) {
27 PrepareSamples(histogram, histogram->SnapshotDelta());
28 }
29
PrepareFinalDelta(const HistogramBase * histogram)30 void HistogramSnapshotManager::PrepareFinalDelta(
31 const HistogramBase* histogram) {
32 PrepareSamples(histogram, histogram->SnapshotFinalDelta());
33 }
34
PrepareSamples(const HistogramBase * histogram,std::unique_ptr<HistogramSamples> samples)35 void 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 uint32_t ranges_checksum = ranges->checksum();
57 uint32_t ranges_calc_checksum = ranges->CalculateChecksum();
58 const char* histogram_name = histogram->histogram_name().c_str();
59 int32_t flags = histogram->flags();
60 // The checksum should have caught this, so crash separately if it didn't.
61 CHECK_NE(0U, HistogramBase::RANGE_CHECKSUM_ERROR & corruption);
62 CHECK(false); // Crash for the bucket order corruption.
63 // Ensure that compiler keeps around pointers to |histogram| and its
64 // internal |bucket_ranges_| for any minidumps.
65 base::debug::Alias(&ranges_ptr);
66 base::debug::Alias(&ranges_checksum);
67 base::debug::Alias(&ranges_calc_checksum);
68 base::debug::Alias(&histogram_name);
69 base::debug::Alias(&flags);
70 }
71 // Checksum corruption might not have caused order corruption.
72 CHECK_EQ(0U, HistogramBase::RANGE_CHECKSUM_ERROR & corruption);
73
74 // Note, at this point corruption can only be COUNT_HIGH_ERROR or
75 // COUNT_LOW_ERROR and they never arise together, so we don't need to extract
76 // bits from corruption.
77 if (corruption) {
78 DLOG(ERROR) << "Histogram: \"" << histogram->histogram_name()
79 << "\" has data corruption: " << corruption;
80 histogram_flattener_->InconsistencyDetected(
81 static_cast<HistogramBase::Inconsistency>(corruption));
82 // Don't record corrupt data to metrics services.
83 const uint32_t old_corruption = sample_info->inconsistencies;
84 if (old_corruption == (corruption | old_corruption))
85 return; // We've already seen this corruption for this histogram.
86 sample_info->inconsistencies |= corruption;
87 histogram_flattener_->UniqueInconsistencyDetected(
88 static_cast<HistogramBase::Inconsistency>(corruption));
89 return;
90 }
91
92 if (samples->TotalCount() > 0)
93 histogram_flattener_->RecordDelta(*histogram, *samples);
94 }
95
InspectLoggedSamplesInconsistency(const HistogramSamples & new_snapshot,HistogramSamples * logged_samples)96 void HistogramSnapshotManager::InspectLoggedSamplesInconsistency(
97 const HistogramSamples& new_snapshot,
98 HistogramSamples* logged_samples) {
99 HistogramBase::Count discrepancy =
100 logged_samples->TotalCount() - logged_samples->redundant_count();
101 if (!discrepancy)
102 return;
103
104 histogram_flattener_->InconsistencyDetectedInLoggedCount(discrepancy);
105 if (discrepancy > Histogram::kCommonRaceBasedCountMismatch) {
106 // Fix logged_samples.
107 logged_samples->Subtract(*logged_samples);
108 logged_samples->Add(new_snapshot);
109 }
110 }
111
112 } // namespace base
113