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 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
InspectLoggedSamplesInconsistency(const HistogramSamples & new_snapshot,HistogramSamples * logged_samples)92 void 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