Track thread activities in order to diagnose hangs.

base/debug/activity_analyzer.h

+// 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) {}

[Mark Mentovai, 2016/08/01 15:59:37]

You’ve gone to some work to disambiguate threads across processes, but the
system’s idea of the thread ID already does this on all platforms we support, so
it should be possible to do this without using process IDs to disambiguate.
Unfortunately, Chrome’s threading support in base doesn’t really use system
thread IDs for much outside of Windows, you’re stuck with pthread handles, which
aren’t unique system-wide.

I wish the world were better, but I guess this ThreadKey thing is necessary for
now.

[bcwhite, 2016/08/01 17:36:11]

Acknowledged.

+
+    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|.
+  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_