[sgen] Fix a concurrent collector bug.

Pinning is done in the worker thread, but reset in the main thread.
The main thread must wait for the worker jobs to finish until it can
reset pinning.  We didn't do this before.

diff --git a/mono/metadata/sgen-gc.c b/mono/metadata/sgen-gc.c
index 94bdd532629b0801ed634e6cdbacf157085fab8e..917baad5b15fc8836a85eb318d46469749520338 100644 (file)
--- a/mono/metadata/sgen-gc.c
+++ b/mono/metadata/sgen-gc.c
@@ -2734,16 +2734,25 @@ major_copy_or_mark_from_roots (size_t *old_next_pin_slot, gboolean start_concurr
 
        TV_GETTIME (btv);
        time_major_scan_big_objects += TV_ELAPSED (atv, btv);
+}
 
-       if (concurrent_collection_in_progress) {
-               /* prepare the pin queue for the next collection */
-               sgen_finish_pinning ();
+static void
+major_finish_copy_or_mark (void)
+{
+       if (!concurrent_collection_in_progress)
+               return;
 
-               sgen_pin_stats_reset ();
+       /*
+        * Prepare the pin queue for the next collection.  Since pinning runs on the worker
+        * threads we must wait for the jobs to finish before we can reset it.
+        */
+       sgen_workers_wait_for_jobs_finished ();
+       sgen_finish_pinning ();
 
-               if (do_concurrent_checks)
-                       check_nursery_is_clean ();
-       }
+       sgen_pin_stats_reset ();
+
+       if (do_concurrent_checks)
+               check_nursery_is_clean ();
 }
 
 static void
@@ -2787,6 +2796,7 @@ major_start_collection (gboolean concurrent, size_t *old_next_pin_slot)
                major_collector.start_major_collection ();
 
        major_copy_or_mark_from_roots (old_next_pin_slot, concurrent, FALSE, FALSE, FALSE);
+       major_finish_copy_or_mark ();
 }
 
 static void
@@ -2814,6 +2824,8 @@ major_finish_collection (const char *reason, size_t old_next_pin_slot, gboolean
                major_copy_or_mark_from_roots (NULL, FALSE, TRUE, scan_mod_union, scan_whole_nursery);
 
                sgen_workers_signal_finish_nursery_collection ();
+
+               major_finish_copy_or_mark ();
                gray_queue_enable_redirect (WORKERS_DISTRIBUTE_GRAY_QUEUE);
 
                sgen_workers_join ();
@@ -3033,7 +3045,6 @@ major_start_concurrent_collection (const char *reason)
        major_start_collection (TRUE, NULL);
 
        gray_queue_redirect (&gray_queue);
-       sgen_workers_wait_for_jobs_finished ();
 
        num_objects_marked = major_collector.get_and_reset_num_major_objects_marked ();
        MONO_GC_CONCURRENT_START_END (GENERATION_OLD, num_objects_marked);