Drqs 176332566/bdlmt multiqueuethreadpool external threadpool shutdow…

…n race (#4914)

* reproduce problem in new test case

* correcting a possible issue in resume, and issue in case 34

* increase number of iterations

* update case 34 doc

groups/bdl/bdlmt/bdlmt_multiqueuethreadpool.cpp

@@ -407,16 +407,17 @@ int MultiQueueThreadPool_Queue::resume()
     }
 
     if (!d_list.empty()) {
+        ++d_multiQueueThreadPool_p->d_numActiveQueues;
+
         int status = d_multiQueueThreadPool_p->d_threadPool_p->
                                                     enqueueJob(d_processingCb);
 
         if (0 != status) {
+            --d_multiQueueThreadPool_p->d_numActiveQueues;
             return 1;                                                 // RETURN
         }
 
         d_runState = e_SCHEDULED;
-
-        ++d_multiQueueThreadPool_p->d_numActiveQueues;
     }
     else {
         d_runState = e_NOT_SCHEDULED;
@@ -472,11 +473,11 @@ void MultiQueueThreadPool::deleteQueueCb(
 
     d_queuePool.releaseObject(queue);
 
+    --d_numActiveQueues;
+
     if (completionSignal) {
         completionSignal->arrive();
     }
-
-    --d_numActiveQueues;
 }
 
 // CREATORS

groups/bdl/bdlmt/bdlmt_multiqueuethreadpool.t.cpp

@@ -114,6 +114,8 @@ using namespace BloombergLP;
 // [30] DRQS 140150365: resume fails immediately after pause
 // [31] DRQS 140403279: pause can deadlock with delete and create
 // [32] DRQS 143578129: 'numElements' stress test
+// [34] DRQS 176332566: external threadpool shutdown race
+// [35] USAGE EXAMPLE 1
 // [-2] PERFORMANCE TEST
 // ----------------------------------------------------------------------------
 
@@ -1499,7 +1501,7 @@ int main(int argc, char *argv[]) {
     bslma::DefaultAllocatorGuard dGuard(&da);
 
     switch (test) { case 0:
-      case 34: {
+      case 35: {
         // --------------------------------------------------------------------
         // TESTING USAGE EXAMPLE 1
         //
@@ -1580,6 +1582,44 @@ int main(int argc, char *argv[]) {
         ASSERT(0 <  ta.numAllocations());
         ASSERT(0 == ta.numBytesInUse());
       }  break;
+      case 34: {
+        // --------------------------------------------------------------------
+        // DRQS 176332566: external threadpool shutdown race
+        //
+        // Concerns:
+        //: 1 Deleting a MQTP using an external thread pool does not have a
+        //:   race condition with jobs in the thread pool.
+        //
+        // Plan:
+        //: 1 Stress test 'bdlmt::MultiQueueThreadPool' deletion when using
+        //:   an external threadpool.
+        //
+        // Testing:
+        //   DRQS 176332566: external threadpool shutdown race
+        // --------------------------------------------------------------------
+
+        if (verbose) {
+            cout << "DRQS 176332566: external threadpool shutdown race\n"
+                 << "=================================================\n";
+        }
+
+        for (int i = 0; i < 1000; ++i) {
+            bslmt::ThreadAttributes defaultAttrs;
+            bdlmt::ThreadPool underlyingPool(defaultAttrs, 2, 2, 0);
+            underlyingPool.start();
+
+            // need to allocate to see data race with 'delete'
+            bdlmt::MultiQueueThreadPool *pool =
+                              new bdlmt::MultiQueueThreadPool(&underlyingPool);
+
+            pool->start();
+            int q = pool->createQueue();
+            pool->enqueueJob(q, noop);
+            pool->shutdown();
+
+            delete pool;
+        }
+      }  break;
       case 33: {
         // --------------------------------------------------------------------
         // TESTING BATCH SIZE