Fix RefCountTest and RCURefCount race

Reviewed By: alikhtarov

Differential Revision: D2741459

fb-gh-sync-id: c4bd068cf735ae25364edba40960096fb35e8c43

diff --git a/folly/experimental/RCURefCount.h b/folly/experimental/RCURefCount.h
index 567006eadf431515c35c58a26e7a2a67a8538268..3814f8199e558e91058ef895b11b01cc34d1de33 100644 (file)
--- a/folly/experimental/RCURefCount.h
+++ b/folly/experimental/RCURefCount.h
@@ -40,12 +40,13 @@ class RCURefCount {
     auto& localCount = *localCount_;
 
     std::lock_guard<RCUReadLock> lg(RCUReadLock::instance());
     auto& localCount = *localCount_;
 
     std::lock_guard<RCUReadLock> lg(RCUReadLock::instance());

+    auto state = state_.load();

 
 

-    if (LIKELY(state_ == State::LOCAL)) {
+    if (LIKELY(state == State::LOCAL)) {

       ++localCount;
 
       return 42;
       ++localCount;
 
       return 42;

-    } else if (state_ == State::GLOBAL_TRANSITION) {
+    } else if (state == State::GLOBAL_TRANSITION) {

       ++globalCount_;
 
       return 42;
       ++globalCount_;
 
       return 42;


@@ -67,15 +68,16 @@ class RCURefCount {
     auto& localCount = *localCount_;
 
     std::lock_guard<RCUReadLock> lg(RCUReadLock::instance());
     auto& localCount = *localCount_;
 
     std::lock_guard<RCUReadLock> lg(RCUReadLock::instance());

+    auto state = state_.load();

 
 

-    if (LIKELY(state_ == State::LOCAL)) {
+    if (LIKELY(state == State::LOCAL)) {

       --localCount;
 
       return 42;
     } else {
       auto value = --globalCount_;
 
       --localCount;
 
       return 42;
     } else {
       auto value = --globalCount_;
 

-      if (state_ == State::GLOBAL) {
+      if (state == State::GLOBAL) {

         assert(value >= 0);
         return value;
       } else {
         assert(value >= 0);
         return value;
       } else {

diff --git a/folly/experimental/test/RefCountTest.cpp b/folly/experimental/test/RefCountTest.cpp
index 48ad80d91e396d3a4667de45670645ecf499b110..6cd72474eb13413c5ad9437cce983bbfa8333eca 100644 (file)
--- a/folly/experimental/test/RefCountTest.cpp
+++ b/folly/experimental/test/RefCountTest.cpp
@@ -69,7 +69,9 @@ void basicTest() {
   b.wait();
 
   count.useGlobal();
   b.wait();
 
   count.useGlobal();

-  --count;
+  if (--count == 0) {
+    ++got0;
+  }

 
   for (auto& t: ts) {
     t.join();
 
   for (auto& t: ts) {
     t.join();