Track thread activities in order to diagnose hangs.

base/debug/activity_analyzer.cc

Index: base/debug/activity_analyzer.cc
diff --git a/base/debug/activity_analyzer.cc b/base/debug/activity_analyzer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..b8a309f95bb5824123180ed4f54efedc7afe374c
--- /dev/null
+++ b/base/debug/activity_analyzer.cc
@@ -0,0 +1,124 @@
+// 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.
+
+#include "base/debug/activity_analyzer.h"
+
+#include "base/files/file.h"
+#include "base/files/file_path.h"
+#include "base/files/memory_mapped_file.h"
+#include "base/logging.h"
+#include "base/memory/ptr_util.h"
+#include "base/stl_util.h"
+#include "base/strings/string_util.h"
+
+namespace base {
+namespace debug {
+
+ThreadActivityAnalyzer::ThreadActivityAnalyzer(
+    const ThreadActivityTracker* tracker)
+    : activity_snapshot_valid_(tracker->Snapshot(&activity_snapshot_)) {}
+
+ThreadActivityAnalyzer::ThreadActivityAnalyzer(void* base, size_t size)
+    : ThreadActivityAnalyzer(
+          WrapUnique(new ThreadActivityTracker(base, size)).get()) {}
+
+ThreadActivityAnalyzer::ThreadActivityAnalyzer(
+    PersistentMemoryAllocator* allocator,
+    PersistentMemoryAllocator::Reference reference)
+    : ThreadActivityAnalyzer(allocator->GetAsObject<char>(
+                                 reference,
+                                 GlobalActivityTracker::kTypeIdActivityTracker),
+                             allocator->GetAllocSize(reference)) {}
+
+ThreadActivityAnalyzer::~ThreadActivityAnalyzer() {}
+
+GlobalActivityAnalyzer::GlobalActivityAnalyzer(
+    std::unique_ptr<PersistentMemoryAllocator> allocator)
+    : allocator_(std::move(allocator)), allocator_iterator_(allocator_.get()) {}
+
+GlobalActivityAnalyzer::~GlobalActivityAnalyzer() {}
+
+#if !defined(OS_NACL)
+std::unique_ptr<GlobalActivityAnalyzer> GlobalActivityAnalyzer::CreateWithFile(
+    const FilePath& file_path) {
+  std::unique_ptr<MemoryMappedFile> mmfile(new MemoryMappedFile());
+  mmfile->Initialize(file_path);
+  if (!mmfile->IsValid())
+    return nullptr;
+
+  if (!FilePersistentMemoryAllocator::IsFileAcceptable(*mmfile, true))
+    return nullptr;
+
+  return WrapUnique(new GlobalActivityAnalyzer(
+             WrapUnique(new FilePersistentMemoryAllocator(
+                            std::move(mmfile), 0, 0, base::StringPiece(),
+                            true))));
+}
+#endif  // !defined(OS_NACL)
+
+ThreadActivityAnalyzer* GlobalActivityAnalyzer::GetFirstAnalyzer() {
+  // Fetch all the records. This will retrieve only ones created since the
+  // last run since the PMA iterator will continue from where it left off.
+  uint32_t type;

[Sigurður Ásgeirsson, 2016/06/14 15:28:12]

Maybe tuck most of the body of this function into a private Snapshot* member
function for readability?

[bcwhite, 2016/06/14 15:54:56]

Ummm...  I specifically said that the activity_analyzer_* code wasn't ready for
review.

[bcwhite, 2016/06/14 19:48:45]

Done.

+  PersistentMemoryAllocator::Reference ref;
+  while ((ref = allocator_iterator_.GetNext(&type)) != 0) {
+    switch (type) {
+      case GlobalActivityTracker::kTypeIdActivityTracker:
+      case GlobalActivityTracker::kTypeIdActivityTrackerFree:
+        // Free or not, add it to the list of references for later analysis.
+        tracker_references_.insert(ref);
+        break;
+    }
+  }
+
+  // Go through all the known references and create analyzers for them with
+  // snapshots of the current state.
+  analyzers_.clear();
+  for (PersistentMemoryAllocator::Reference tracker_ref : tracker_references_) {
+    // Get the actual data segment for the tracker. This can fail if the
+    // record has been marked "free" since the type will not match.
+    void* base = allocator_->GetAsObject<char>(
+        tracker_ref, GlobalActivityTracker::kTypeIdActivityTracker);
+    if (!base)
+      continue;
+
+    // Create the analyzer on the data. This will capture a snapshot of the
+    // tracker state. This can fail if the tracker is somehow corrupted or is
+    // in the process of shutting down.
+    std::unique_ptr<ThreadActivityAnalyzer> analyzer(new ThreadActivityAnalyzer(
+        base, allocator_->GetAllocSize(tracker_ref)));
+    if (!analyzer->IsValid())
+      continue;
+
+    // Add this analyzer to the map of known ones, indexed by a unique thread
+    // identifier.
+    analyzer->allocator_reference_ = ref;
+    analyzers_[analyzer->GetThreadKey()] = std::move(analyzer);

[Sigurður Ásgeirsson, 2016/06/14 15:28:12]

not having read the analyzer code, it's not clear to me that GetThreadKey is
necessarily unique. What would be the consequences of non-unique keys here?

[bcwhite, 2016/06/14 19:48:45]

Only active (currently executing) trackers are included and so there is no
duplication.

A non-unique key would simply point to the last one found.  Confusing, sure, but
not fatal.  It shouldn't happen.

+  }
+
+  // Set up the iterator for going through all the analyzers.
+  analyzers_iterator_ = analyzers_.begin();
+  if (analyzers_iterator_ == analyzers_.end())
+    return nullptr;
+  return analyzers_iterator_->second.get();
+}
+
+ThreadActivityAnalyzer* GlobalActivityAnalyzer::GetNextAnalyzer() {
+  DCHECK(analyzers_iterator_ != analyzers_.end());
+  ++analyzers_iterator_;
+  if (analyzers_iterator_ == analyzers_.end())
+    return nullptr;
+  return analyzers_iterator_->second.get();
+}
+
+ThreadActivityAnalyzer* GlobalActivityAnalyzer::GetAnalyzerForThread(
+    const ThreadKey& key) {
+  auto found = analyzers_.find(key);
+  if (found == analyzers_.end())
+    return nullptr;
+  return found->second.get();
+}
+
+}  // namespace debug
+}  // namespace base