Move the call to heapCensus() into GarbageCollect(), just before

calling resurrectThreads() (fixes #5314).

This avoids a lot of problems, because resurrectThreads() may
overwrite some closures in the heap, leaving slop behind.  The bug in
instances, this fix avoids them all in one go.

1 files changed, 10 insertions, 0 deletions

diff --git a/rts/sm/GC.c b/rts/sm/GC.c
index 9f69a4c65a..396992ca01 100644
--- a/rts/sm/GC.c
+++ b/rts/sm/GC.c
@@ -171,6 +171,7 @@ StgPtr mark_sp;            // pointer to the next unallocated mark stack entry
 
 void
 GarbageCollect (rtsBool force_major_gc, 
+                rtsBool do_heap_census,
                 nat gc_type USED_IF_THREADS,
                 Capability *cap)
 {
@@ -661,6 +662,15 @@ GarbageCollect (rtsBool force_major_gc,
   // fill slop.
   IF_DEBUG(sanity, checkSanity(rtsTrue /* after GC */, major_gc));
 
+  // If a heap census is due, we need to do it before
+  // resurrectThreads(), for the same reason as checkSanity above:
+  // resurrectThreads() will overwrite some closures and leave slop
+  // behind.
+  if (do_heap_census) {
+      debugTrace(DEBUG_sched, "performing heap census");
+      heapCensus();
+  }
+
   // send exceptions to any threads which were about to die
   RELEASE_SM_LOCK;
   resurrectThreads(resurrected_threads);