Add hooks to track which threads belong to which thread pools

Summary:
Keep track of which threads belong to which thread pools for use when debugging.
This will be paired with a gdb script that associates threads with their thread pools

Reviewed By: andriigrynenko

Differential Revision: D5514729

fbshipit-source-id: 57ada4dd1aaaec5d7026e4eee05b0ec4e7434c77

diff --git a/folly/GlobalThreadPoolList.cpp b/folly/GlobalThreadPoolList.cpp
new file mode 100644 (file)
index 0000000..075baa7
--- /dev/null
+++ b/folly/GlobalThreadPoolList.cpp
@@ -0,0 +1,218 @@
+/*
+ * Copyright 2017 Facebook, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <folly/GlobalThreadPoolList.h>
+
+#include <memory>
+#include <string>
+#include <vector>
+
+#include <folly/CppAttributes.h>
+#include <folly/Indestructible.h>
+#include <folly/Synchronized.h>
+#include <folly/ThreadLocal.h>
+
+namespace folly {
+
+namespace {
+
+class ThreadListHook {
+ public:
+  ThreadListHook(ThreadPoolListHook* poolId, std::thread::id threadId);
+  ~ThreadListHook();
+
+ private:
+  ThreadListHook() {}
+  ThreadPoolListHook* poolId_;
+  std::thread::id threadId_;
+};
+
+class GlobalThreadPoolListImpl {
+ public:
+  GlobalThreadPoolListImpl() {}
+
+  void registerThreadPool(ThreadPoolListHook* threadPoolId, std::string name);
+
+  void unregisterThreadPool(ThreadPoolListHook* threadPoolId);
+
+  void registerThreadPoolThread(
+      ThreadPoolListHook* threadPoolId,
+      std::thread::id threadId);
+
+  void unregisterThreadPoolThread(
+      ThreadPoolListHook* threadPoolId,
+      std::thread::id threadId);
+
+ private:
+  struct PoolInfo {
+    ThreadPoolListHook* addr;
+    std::string name;
+    std::vector<std::thread::id> threads;
+  };
+
+  struct Pools {
+    // Just a vector since ease of access from gdb is the most important
+    // property
+    std::vector<PoolInfo> poolsInfo_;
+
+    std::vector<std::thread::id>* FOLLY_NULLABLE
+    getThreadVector(void* threadPoolId) {
+      for (auto& elem : vector()) {
+        if (elem.addr == threadPoolId) {
+          return &elem.threads;
+        }
+      }
+
+      return nullptr;
+    }
+
+    std::vector<PoolInfo>& vector() {
+      return poolsInfo_;
+    }
+  };
+
+  Pools pools_;
+};
+
+class GlobalThreadPoolList {
+ public:
+  GlobalThreadPoolList() {}
+
+  static GlobalThreadPoolList& instance();
+
+  void registerThreadPool(ThreadPoolListHook* threadPoolId, std::string name);
+
+  void unregisterThreadPool(ThreadPoolListHook* threadPoolId);
+
+  void registerThreadPoolThread(
+      ThreadPoolListHook* threadPoolId,
+      std::thread::id threadId);
+
+  void unregisterThreadPoolThread(
+      ThreadPoolListHook* threadPoolId,
+      std::thread::id threadId);
+
+  GlobalThreadPoolList(GlobalThreadPoolList const&) = delete;
+  void operator=(GlobalThreadPoolList const&) = delete;
+
+ private:
+  folly::Synchronized<GlobalThreadPoolListImpl> globalListImpl_;
+  folly::ThreadLocalPtr<ThreadListHook> threadHook_;
+};
+
+} // namespace
+
+GlobalThreadPoolList& GlobalThreadPoolList::instance() {
+  static folly::Indestructible<GlobalThreadPoolList> ret;
+  return *ret;
+}
+
+void GlobalThreadPoolList::registerThreadPool(
+    ThreadPoolListHook* threadPoolId,
+    std::string name) {
+  globalListImpl_->registerThreadPool(threadPoolId, name);
+}
+
+void GlobalThreadPoolList::unregisterThreadPool(
+    ThreadPoolListHook* threadPoolId) {
+  globalListImpl_->unregisterThreadPool(threadPoolId);
+}
+
+void GlobalThreadPoolList::registerThreadPoolThread(
+    ThreadPoolListHook* threadPoolId,
+    std::thread::id threadId) {
+  DCHECK(!threadHook_);
+  threadHook_.reset(make_unique<ThreadListHook>(threadPoolId, threadId));
+
+  globalListImpl_->registerThreadPoolThread(threadPoolId, threadId);
+}
+
+void GlobalThreadPoolList::unregisterThreadPoolThread(
+    ThreadPoolListHook* threadPoolId,
+    std::thread::id threadId) {
+  (void)threadPoolId;
+  (void)threadId;
+  globalListImpl_->unregisterThreadPoolThread(threadPoolId, threadId);
+}
+
+void GlobalThreadPoolListImpl::registerThreadPool(
+    ThreadPoolListHook* threadPoolId,
+    std::string name) {
+  PoolInfo info;
+  info.name = name;
+  info.addr = threadPoolId;
+  pools_.vector().push_back(info);
+}
+
+void GlobalThreadPoolListImpl::unregisterThreadPool(
+    ThreadPoolListHook* threadPoolId) {
+  auto& vector = pools_.vector();
+  vector.erase(
+      std::remove_if(
+          vector.begin(),
+          vector.end(),
+          [=](PoolInfo& i) { return i.addr == threadPoolId; }),
+      vector.end());
+}
+
+void GlobalThreadPoolListImpl::registerThreadPoolThread(
+    ThreadPoolListHook* threadPoolId,
+    std::thread::id threadId) {
+  auto vec = pools_.getThreadVector(threadPoolId);
+  if (vec == nullptr) {
+    return;
+  }
+
+  vec->push_back(threadId);
+}
+
+void GlobalThreadPoolListImpl::unregisterThreadPoolThread(
+    ThreadPoolListHook* threadPoolId,
+    std::thread::id threadId) {
+  auto vec = pools_.getThreadVector(threadPoolId);
+  if (vec == nullptr) {
+    return;
+  }
+
+  vec->erase(std::remove(vec->begin(), vec->end(), threadId), vec->end());
+}
+
+ThreadListHook::ThreadListHook(
+    ThreadPoolListHook* poolId,
+    std::thread::id threadId) {
+  poolId_ = poolId;
+  threadId_ = threadId;
+}
+
+ThreadListHook::~ThreadListHook() {
+  GlobalThreadPoolList::instance().unregisterThreadPoolThread(
+      poolId_, threadId_);
+}
+
+ThreadPoolListHook::ThreadPoolListHook(std::string name) {
+  GlobalThreadPoolList::instance().registerThreadPool(this, name);
+}
+
+ThreadPoolListHook::~ThreadPoolListHook() {
+  GlobalThreadPoolList::instance().unregisterThreadPool(this);
+}
+
+void ThreadPoolListHook::registerThread() {
+  GlobalThreadPoolList::instance().registerThreadPoolThread(
+      this, std::this_thread::get_id());
+}
+
+} // folly

diff --git a/folly/GlobalThreadPoolList.h b/folly/GlobalThreadPoolList.h
new file mode 100644 (file)
index 0000000..8e13df0
--- /dev/null
+++ b/folly/GlobalThreadPoolList.h
@@ -0,0 +1,61 @@
+/*
+ * Copyright 2017 Facebook, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <memory>
+#include <string>
+#include <vector>
+
+#include <folly/Indestructible.h>
+#include <folly/Synchronized.h>
+#include <folly/ThreadLocal.h>
+
+namespace folly {
+
+/**
+ * A hook for tracking which threads belong to which thread pools.
+ * This is used only by a gdb extension to aid in debugging. You won't be able
+ * to see any useful information from within C++ code.
+ *
+ * An instance of ThreadPoolListHook should be created in the thread pool class
+ * that you want to keep track of. Then, to register a thread you call
+ * registerThread() on your instance of ThreadPoolListHook from that thread.
+ *
+ * When a thread exits it will be removed from the list
+ * When the thread pool is destroyed, it will be removed from the list
+ */
+class ThreadPoolListHook {
+ public:
+  /**
+   * Name is used to identify the thread pool when listing threads.
+   */
+  explicit ThreadPoolListHook(std::string name);
+  ~ThreadPoolListHook();
+
+  /**
+   * Call this from any new thread that the thread pool creates.
+   */
+  void registerThread();
+
+  ThreadPoolListHook(const ThreadPoolListHook& other) = delete;
+  ThreadPoolListHook& operator=(const ThreadPoolListHook&) = delete;
+
+ private:
+  ThreadPoolListHook();
+};
+
+} // folly