Fix race in WebRTC logging.
[chromium-blink-merge.git] / base / metrics / histogram_snapshot_manager.cc
blobb1e26da59dcf30d70be39390e742297e17cb6926
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.
5 #include "base/metrics/histogram_snapshot_manager.h"
7 #include "base/memory/scoped_ptr.h"
8 #include "base/metrics/histogram_flattener.h"
9 #include "base/metrics/histogram_samples.h"
10 #include "base/metrics/statistics_recorder.h"
11 #include "base/stl_util.h"
13 using std::map;
14 using std::string;
16 namespace base {
18 HistogramSnapshotManager::HistogramSnapshotManager(
19 HistogramFlattener* histogram_flattener)
20 : histogram_flattener_(histogram_flattener) {
21 DCHECK(histogram_flattener_);
24 HistogramSnapshotManager::~HistogramSnapshotManager() {
25 STLDeleteValues(&logged_samples_);
28 void HistogramSnapshotManager::PrepareDeltas(
29 HistogramBase::Flags flag_to_set,
30 HistogramBase::Flags required_flags) {
31 StatisticsRecorder::Histograms histograms;
32 StatisticsRecorder::GetHistograms(&histograms);
33 for (StatisticsRecorder::Histograms::const_iterator it = histograms.begin();
34 histograms.end() != it;
35 ++it) {
36 (*it)->SetFlags(flag_to_set);
37 if (((*it)->flags() & required_flags) == required_flags)
38 PrepareDelta(**it);
42 void HistogramSnapshotManager::PrepareDelta(const HistogramBase& histogram) {
43 DCHECK(histogram_flattener_);
45 // Get up-to-date snapshot of sample stats.
46 scoped_ptr<HistogramSamples> snapshot(histogram.SnapshotSamples());
47 const std::string& histogram_name = histogram.histogram_name();
49 int corruption = histogram.FindCorruption(*snapshot);
51 // Crash if we detect that our histograms have been overwritten. This may be
52 // a fair distance from the memory smasher, but we hope to correlate these
53 // crashes with other events, such as plugins, or usage patterns, etc.
54 if (HistogramBase::BUCKET_ORDER_ERROR & corruption) {
55 // The checksum should have caught this, so crash separately if it didn't.
56 CHECK_NE(0, HistogramBase::RANGE_CHECKSUM_ERROR & corruption);
57 CHECK(false); // Crash for the bucket order corruption.
59 // Checksum corruption might not have caused order corruption.
60 CHECK_EQ(0, HistogramBase::RANGE_CHECKSUM_ERROR & corruption);
62 // Note, at this point corruption can only be COUNT_HIGH_ERROR or
63 // COUNT_LOW_ERROR and they never arise together, so we don't need to extract
64 // bits from corruption.
65 if (corruption) {
66 DLOG(ERROR) << "Histogram: " << histogram_name
67 << " has data corruption: " << corruption;
68 histogram_flattener_->InconsistencyDetected(
69 static_cast<HistogramBase::Inconsistency>(corruption));
70 // Don't record corrupt data to metrics services.
71 int old_corruption = inconsistencies_[histogram_name];
72 if (old_corruption == (corruption | old_corruption))
73 return; // We've already seen this corruption for this histogram.
74 inconsistencies_[histogram_name] |= corruption;
75 histogram_flattener_->UniqueInconsistencyDetected(
76 static_cast<HistogramBase::Inconsistency>(corruption));
77 return;
80 HistogramSamples* to_log;
81 map<string, HistogramSamples*>::iterator it =
82 logged_samples_.find(histogram_name);
83 if (it == logged_samples_.end()) {
84 to_log = snapshot.release();
86 // This histogram has not been logged before, add a new entry.
87 logged_samples_[histogram_name] = to_log;
88 } else {
89 HistogramSamples* already_logged = it->second;
90 InspectLoggedSamplesInconsistency(*snapshot, already_logged);
91 snapshot->Subtract(*already_logged);
92 already_logged->Add(*snapshot);
93 to_log = snapshot.get();
96 if (to_log->TotalCount() > 0)
97 histogram_flattener_->RecordDelta(histogram, *to_log);
100 void HistogramSnapshotManager::InspectLoggedSamplesInconsistency(
101 const HistogramSamples& new_snapshot,
102 HistogramSamples* logged_samples) {
103 HistogramBase::Count discrepancy =
104 logged_samples->TotalCount() - logged_samples->redundant_count();
105 if (!discrepancy)
106 return;
108 histogram_flattener_->InconsistencyDetectedInLoggedCount(discrepancy);
109 if (discrepancy > Histogram::kCommonRaceBasedCountMismatch) {
110 // Fix logged_samples.
111 logged_samples->Subtract(*logged_samples);
112 logged_samples->Add(new_snapshot);
116 } // namespace base