From 862813847a4302f4c60b80c5b0b2bd31b89cd7ea Mon Sep 17 00:00:00 2001
From: Yutian Li <hotpxless@gmail.com>
Date: Sun, 30 Aug 2015 03:14:53 +0800
Subject: [PATCH] [simple-engine] fix counter

---
 src/dag_engine/simple_engine.cc | 10 +++++-----
 src/dag_engine/simple_engine.h  |  5 +----
 2 files changed, 6 insertions(+), 9 deletions(-)

diff --git a/src/dag_engine/simple_engine.cc b/src/dag_engine/simple_engine.cc
index fbdcd4b81430..36eea89fd849 100644
--- a/src/dag_engine/simple_engine.cc
+++ b/src/dag_engine/simple_engine.cc
@@ -188,8 +188,8 @@ void SimpleEngine::OnComplete(SimpleOpr* simple_opr) {
    * Mark complete for read variables.
    */
   for (auto&& i : simple_opr->use_vars) {
+    std::lock_guard<std::mutex> lock{i->m};
     if (--i->num_pending_reads == 0) {
-      std::lock_guard<std::mutex> lock{i->m};
       if (i->pending_write != nullptr &&
           --i->pending_write->trigger->wait == 0) {
         task_queue_.Push(i->pending_write->trigger);
@@ -200,7 +200,7 @@ void SimpleEngine::OnComplete(SimpleOpr* simple_opr) {
    * Mark complete for write variables.
    */
   for (auto&& i : simple_opr->mutate_vars) {
-    SimpleVar* to_delete = nullptr;
+    bool to_delete = false;
     {
       std::lock_guard<std::mutex> lock{i->m};
       assert(i->ready_to_read == false);
@@ -210,7 +210,7 @@ void SimpleEngine::OnComplete(SimpleOpr* simple_opr) {
       if (i->to_delete) {
         assert(head->next == nullptr);
         delete head;
-        to_delete = i;
+        to_delete = true;
       } else {
         while (true) {
           if (head->write == true) {
@@ -237,8 +237,8 @@ void SimpleEngine::OnComplete(SimpleOpr* simple_opr) {
         }
       }
     }
-    if (to_delete != nullptr) {
-      delete to_delete;
+    if (to_delete) {
+      delete i;
     }
   }
   {
diff --git a/src/dag_engine/simple_engine.h b/src/dag_engine/simple_engine.h
index 30996ece3007..21af488f1c1d 100644
--- a/src/dag_engine/simple_engine.h
+++ b/src/dag_engine/simple_engine.h
@@ -62,11 +62,8 @@ struct SimpleVar final : public Var {
   SimpleVar() { LOG(INFO) << __func__ << " " << ++counter; }
   ~SimpleVar() { LOG(INFO) << __func__ << " " << --counter; }
 #endif  // DAG_ENGINE_DEBUG
-  std::atomic<std::size_t> num_pending_reads{0};
-  /*!
-   * Protects everything except `num_pending_reads`.
-   */
   std::mutex m;
+  std::size_t num_pending_reads{0};
   VersionedVarBlock* head{nullptr};
   VersionedVarBlock* pending_write{nullptr};
   /*!