Fix endless wait in RenameThreadPool (#2675)

src/util.cpp

@@ -907,18 +907,37 @@ void RenameThreadPool(ctpl::thread_pool& tp, const char* baseName)
     auto cond = std::make_shared<std::condition_variable>();
     auto mutex = std::make_shared<std::mutex>();
     std::atomic<int> doneCnt(0);
-    for (size_t i = 0; i < tp.size(); i++) {
-        tp.push([baseName, i, cond, mutex, &doneCnt](int threadId) {
+    std::map<int, std::future<void> > futures;
+
+    for (int i = 0; i < tp.size(); i++) {
+        futures[i] = tp.push([baseName, i, cond, mutex, &doneCnt](int threadId) {
             RenameThread(strprintf("%s-%d", baseName, i).c_str());
-            doneCnt++;
             std::unique_lock<std::mutex> l(*mutex);
+            doneCnt++;
             cond->wait(l);
         });
     }
-    while (doneCnt != tp.size()) {
+
+    do {
+        // Always sleep to let all threads acquire locks
         MilliSleep(10);
-    }
+        // `doneCnt` should be at least `futures.size()` if tp size was increased (for whatever reason),
+        // or at least `tp.size()` if tp size was decreased and queue was cleared
+        // (which can happen on `stop()` if we were not fast enough to get all jobs to their threads).
+    } while (doneCnt < futures.size() && doneCnt < tp.size());
+
     cond->notify_all();
+
+    // Make sure no one is left behind, just in case
+    for (auto& pair : futures) {
+        auto& f = pair.second;
+        if (f.valid() && f.wait_for(std::chrono::milliseconds(2000)) == std::future_status::timeout) {
+            LogPrintf("%s: %s-%d timed out\n", __func__, baseName, pair.first);
+            // Notify everyone again
+            cond->notify_all();
+            break;
+        }
+    }
 }
 
 void SetupEnvironment()