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