[Router] Fixed the Segfault Bug in Parallel Connection Router

vpr/src/route/parallel_connection_router.h

@@ -218,13 +218,29 @@ class ParallelConnectionRouter : public ConnectionRouter<MultiQueueDAryHeap<Heap
         this->sub_threads_.resize(multi_queue_num_threads - 1);
         for (int i = 0; i < multi_queue_num_threads - 1; ++i) {
             this->sub_threads_[i] = std::thread(&ParallelConnectionRouter::timing_driven_find_single_shortest_path_from_heap_sub_thread_wrapper, this, i + 1 /*0: main thread*/);
-            this->sub_threads_[i].detach();
         }
     }
 
     ~ParallelConnectionRouter() {
         this->is_router_destroying_ = true; // signal the helper threads to exit
         this->thread_barrier_.wait();       // wait until all threads reach the barrier
+        for (auto& sub_thread : this->sub_threads_) {
+            VTR_ASSERT(sub_thread.joinable());
+            // Wait for all helper threads to terminate
+            //
+            // IMPORTANT: This must be done before the main thread destructs this object,
+            // otherwise, helper threads might have access to polluted data members, leading
+            // to undefined behavior. In some cases, due to timing issues between threads,
+            // for example, after both main and helper threads hit the barrier, the main
+            // thread completes object destruction/cleanup before helper threads can check
+            // `this->is_router_destroying_ == true` in `..._sub_thread_wrapper` function,
+            // helper threads may still see `this->is_router_destroying_` as false and fail
+            // to exit their thread functions. This results in helper threads remaining alive
+            // and accessing invalid memory addresses, leading to segfaults (please refer to
+            // https://github.com/verilog-to-routing/vtr-verilog-to-routing/issues/3029 for
+            // details).
+            sub_thread.join();
+        }
 
         VTR_LOG("Parallel Connection Router is being destroyed. Time spent on path search: %.3f seconds.\n",
                 std::chrono::duration<float /*convert to seconds by default*/>(this->path_search_cumulative_time).count());

vtr_flow/tasks/regression_tests/vtr_reg_strong/strong_multiclock/config/config.txt

@@ -28,6 +28,6 @@ script_params_common=-starting_stage vpr -sdc_file tasks/regression_tests/vtr_re
 script_params_list_add =
 script_params_list_add = --route_chan_width 30 -check_incremental_sta_consistency
 script_params_list_add = --router_algorithm parallel --num_workers 4
-# script_params_list_add = --enable_parallel_connection_router on --astar_fac 0.0 --post_target_prune_fac 0.0 --post_target_prune_offset 0.0
-# script_params_list_add = --enable_parallel_connection_router on --multi_queue_num_threads 2 --multi_queue_num_queues 4 --astar_fac 0.0 --post_target_prune_fac 0.0 --post_target_prune_offset 0.0
-# script_params_list_add = --enable_parallel_connection_router on --multi_queue_num_threads 2 --multi_queue_num_queues 8 --multi_queue_direct_draining on --astar_fac 0.0 --post_target_prune_fac 0.0 --post_target_prune_offset 0.0
+script_params_list_add = --enable_parallel_connection_router on --astar_fac 0.0 --post_target_prune_fac 0.0 --post_target_prune_offset 0.0
+script_params_list_add = --enable_parallel_connection_router on --multi_queue_num_threads 2 --multi_queue_num_queues 4 --astar_fac 0.0 --post_target_prune_fac 0.0 --post_target_prune_offset 0.0
+script_params_list_add = --enable_parallel_connection_router on --multi_queue_num_threads 2 --multi_queue_num_queues 8 --multi_queue_direct_draining on --astar_fac 0.0 --post_target_prune_fac 0.0 --post_target_prune_offset 0.0

vtr_flow/tasks/regression_tests/vtr_reg_strong/strong_multiclock/config/golden_results.txt

@@ -2,3 +2,6 @@
  k6_frac_N10_mem32K_40nm.xml	  multiclock.blif	  common	  1.59919	  0.595	  0.841581	  -1	  -1	  0.57	  0.814813	  -1	  1.59919	  -1	  1.1662	  -1	  1.8371	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  0.243	  1.71958	  -1	  -1	  0.268	  3.24281	  -1	  1.44782	  -1	  3.4042	  -1	  -1.40928	  -1	  -1	  -1	  -1	 
  k6_frac_N10_mem32K_40nm.xml	  multiclock.blif	  common_--route_chan_width_30_-check_incremental_sta_consistency	  1.3344	  0.595	  0.781297	  -1	  -1	  0.57	  0.757256	  -1	  1.3344	  -1	  1.16524	  -1	  1.77873	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  0.243	  1.6593	  -1	  -1	  0.268	  3.18526	  -1	  1.18303	  -1	  3.40324	  -1	  -1.46764	  -1	  -1	  -1	  -1	 
  k6_frac_N10_mem32K_40nm.xml	  multiclock.blif	  common_--router_algorithm_parallel_--num_workers_4	  1.59919	  0.595	  0.841581	  -1	  -1	  0.57	  0.814813	  -1	  1.59919	  -1	  1.14847	  -1	  1.95678	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  0.243	  1.71958	  -1	  -1	  0.268	  3.24281	  -1	  1.44782	  -1	  3.38647	  -1	  -1.28959	  -1	  -1	  -1	  -1	 
+ k6_frac_N10_mem32K_40nm.xml	  multiclock.blif	  common_--enable_parallel_connection_router_on_--astar_fac_0.0_--post_target_prune_fac_0.0_--post_target_prune_offset_0.0	  1.59919	  0.595	  0.841581	  -1	  -1	  0.57	  0.814813	  -1	  1.59919	  -1	  1.14847	  -1	  1.95678	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  0.243	  1.71958	  -1	  -1	  0.268	  3.24281	  -1	  1.44782	  -1	  3.38647	  -1	  -1.28959	  -1	  -1	  -1	  -1	 
+ k6_frac_N10_mem32K_40nm.xml	  multiclock.blif	  common_--enable_parallel_connection_router_on_--multi_queue_num_threads_2_--multi_queue_num_queues_4_--astar_fac_0.0_--post_target_prune_fac_0.0_--post_target_prune_offset_0.0	  1.59919	  0.595	  0.841581	  -1	  -1	  0.57	  0.814813	  -1	  1.59919	  -1	  1.14847	  -1	  1.95678	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  0.243	  1.71958	  -1	  -1	  0.268	  3.24281	  -1	  1.44782	  -1	  3.38647	  -1	  -1.28959	  -1	  -1	  -1	  -1	 
+ k6_frac_N10_mem32K_40nm.xml	  multiclock.blif	  common_--enable_parallel_connection_router_on_--multi_queue_num_threads_2_--multi_queue_num_queues_8_--multi_queue_direct_draining_on_--astar_fac_0.0_--post_target_prune_fac_0.0_--post_target_prune_offset_0.0	  1.59919	  0.595	  0.841581	  -1	  -1	  0.57	  0.814813	  -1	  1.59919	  -1	  1.14847	  -1	  1.95678	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  -1	  0.243	  1.71958	  -1	  -1	  0.268	  3.24281	  -1	  1.44782	  -1	  3.38647	  -1	  -1.28959	  -1	  -1	  -1	  -1