Track thread activities in order to diagnose hangs.

base/debug/activity_analyzer.h

Index: base/debug/activity_analyzer.h
diff --git a/base/debug/activity_analyzer.h b/base/debug/activity_analyzer.h
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+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_DEBUG_ACTIVITY_ANALYZER_H_
+#define BASE_DEBUG_ACTIVITY_ANALYZER_H_
+
+#include <map>
+#include <memory>
+#include <set>
+
+#include "base/base_export.h"
+#include "base/debug/activity_tracker.h"
+
+namespace base {
+namespace debug {
+
+// This class provides analysis of data captured from a ThreadActivityTracker.
+// When created, it takes a snapshot of the data held by the tracker and
+// makes that information available to other code.
+class BASE_EXPORT ThreadActivityAnalyzer {
+ public:
+  using Activity = ThreadActivityTracker::Activity;
+  using ActivitySnapshot = ThreadActivityTracker::ActivitySnapshot;
+
+  // This class provides keys that uniquely identify a thread, even across
+  // multiple processes.
+  class ThreadKey {
+   public:
+    ThreadKey(int64_t pid, int64_t tid) : pid_(pid), tid_(tid) {}
+
+    bool operator<(const ThreadKey& rhs) const {
+      if (pid_ != rhs.pid_)
+        return pid_ < rhs.pid_;
+      return tid_ < rhs.tid_;
+    }
+
+    bool operator==(const ThreadKey& rhs) const {
+      return (pid_ == rhs.pid_ && tid_ == rhs.tid_);
+    }
+
+   private:
+    int64_t pid_;
+    int64_t tid_;
+  };
+
+  // Creates an analyzer for an existing activity |tracker|. A snapshot is taken
+  // immediately and the tracker is not referenced again.
+  explicit ThreadActivityAnalyzer(const ThreadActivityTracker& tracker);
+
+  // Creates an analyzer for a block of memory currently or previously in-use
+  // by an activity-tracker. A snapshot is taken immediately and the memory
+  // is not referenced again.
+  ThreadActivityAnalyzer(void* base, size_t size);
+
+  // Creates an analyzer for a block of memory held within a persistent-memory
+  // |allocator| at the given |reference|. A snapshot is taken immediately and
+  // the memory is not referenced again.
+  ThreadActivityAnalyzer(PersistentMemoryAllocator* allocator,
+                         PersistentMemoryAllocator::Reference reference);
+
+  ~ThreadActivityAnalyzer();
+
+  // Returns true iff the contained data is valid. Results from all other
+  // methods are undefined if this returns false.
+  bool IsValid() { return activity_snapshot_valid_; }
+
+  // Gets the name of the thread.
+  const std::string& GetThreadName() {
+    return activity_snapshot_.thread_name;
+  }
+
+  // Gets the TheadKey for this thread.
+  ThreadKey GetThreadKey() {
+    return ThreadKey(activity_snapshot_.process_id,
+                     activity_snapshot_.thread_id);
+  }
+
+ private:
+  friend class GlobalActivityAnalyzer;
+
+  // The snapshot of the activity tracker taken at the moment of construction.
+  ActivitySnapshot activity_snapshot_;
+
+  // Flag indicating if the snapshot data is valid.
+  bool activity_snapshot_valid_;
+
+  // A reference into a persistent memory allocator, used by the global
+  // analyzer to know where this tracker came from.
+  PersistentMemoryAllocator::Reference allocator_reference_ = 0;
+
+  DISALLOW_COPY_AND_ASSIGN(ThreadActivityAnalyzer);
+};
+
+
+// This class manages analyzers for all known processes and threads as stored
+// in a persistent memory allocator. It supports retrieval of them through
+// iteration and directly using a ThreadKey, which allows for cross-references
+// to be resolved.
+// Note that though atomic snapshots are used and everything has its snapshot
+// taken at the same time, the multi-snapshot itself is not atomic and thus may
+// show small inconsistencies between threads if attempted on a live system.
+class BASE_EXPORT GlobalActivityAnalyzer {
+ public:
+  using ThreadKey = ThreadActivityAnalyzer::ThreadKey;
+
+  // Creates a global analyzer from a persistent memory allocator.
+  explicit GlobalActivityAnalyzer(
+      std::unique_ptr<PersistentMemoryAllocator> allocator);
+
+  ~GlobalActivityAnalyzer();
+
+#if !defined(OS_NACL)
+  // Creates a global analyzer using the contents of a file given in
+  // |file_path|.
+  static std::unique_ptr<GlobalActivityAnalyzer> CreateWithFile(
+      const FilePath& file_path);
+#endif  // !defined(OS_NACL)
+
+  // Iterates over all known analyzers or returns null if there are no more.
+  // Ownership stays with the global analyzer object and all existing analyzer
+  // pointers are invalidated when GetFirstAnalyzer() is called.
+  ThreadActivityAnalyzer* GetFirstAnalyzer();
+  ThreadActivityAnalyzer* GetNextAnalyzer();
+
+  // Gets the analyzer for a specific thread or null if there is none.
+  // Ownership stays with the global analyzer object.
+  ThreadActivityAnalyzer* GetAnalyzerForThread(const ThreadKey& key);
+
+ private:
+  using AnalyzerMap =
+      std::map<ThreadKey, std::unique_ptr<ThreadActivityAnalyzer>>;
+
+  // Finds, creates, and indexes analyzers for all known processes and threads.
+  void PrepareAllAnalyzers();
+
+  // The persistent memory allocator holding all tracking data.
+  std::unique_ptr<PersistentMemoryAllocator> allocator_;
+
+  // The iterator for finding tracking information in the allocator.
+  PersistentMemoryAllocator::Iterator allocator_iterator_;
+
+  // A set of all tracker memory references found within the allocator.
+  std::set<PersistentMemoryAllocator::Reference> tracker_references_;
+
+  // A map, keyed by ThreadKey, of all valid activity analyzers.
+  AnalyzerMap analyzers_;
+
+  // The iterator within the analyzers_ map for returning analyzers through
+  // first/next iteration.
+  AnalyzerMap::iterator analyzers_iterator_;
+
+  DISALLOW_COPY_AND_ASSIGN(GlobalActivityAnalyzer);
+};
+
+}  // namespace debug
+}  // namespace base
+
+#endif  // BASE_DEBUG_ACTIVITY_ANALYZER_H_