6882730: G1: parallel heap verification messes up region dump

Summary: It tidies up the G1 heap verification a bit. In particular, when the verification is done in parallel and there is a failure, this is propagated to the top level and the heap is dumped at the end, not by every thread that encounters a failure.
Reviewed-by: johnc, jmasa

src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp

@@ -2210,40 +2210,58 @@ private:
   bool _allow_dirty;
   bool _par;
   bool _use_prev_marking;
+  bool _failures;
 public:
   // use_prev_marking == true  -> use "prev" marking information,
   // use_prev_marking == false -> use "next" marking information
   VerifyRegionClosure(bool allow_dirty, bool par, bool use_prev_marking)
     : _allow_dirty(allow_dirty),
       _par(par),
-      _use_prev_marking(use_prev_marking) {}
+      _use_prev_marking(use_prev_marking),
+      _failures(false) {}
+
+  bool failures() {
+    return _failures;
+  }
 
   bool doHeapRegion(HeapRegion* r) {
     guarantee(_par || r->claim_value() == HeapRegion::InitialClaimValue,
               "Should be unclaimed at verify points.");
     if (!r->continuesHumongous()) {
-      VerifyObjsInRegionClosure not_dead_yet_cl(r, _use_prev_marking);
-      r->verify(_allow_dirty, _use_prev_marking);
-      r->object_iterate(&not_dead_yet_cl);
-      guarantee(r->max_live_bytes() >= not_dead_yet_cl.live_bytes(),
-                "More live objects than counted in last complete marking.");
+      bool failures = false;
+      r->verify(_allow_dirty, _use_prev_marking, &failures);
+      if (failures) {
+        _failures = true;
+      } else {
+        VerifyObjsInRegionClosure not_dead_yet_cl(r, _use_prev_marking);
+        r->object_iterate(&not_dead_yet_cl);
+        if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
+          gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
+                                 "max_live_bytes "SIZE_FORMAT" "
+                                 "< calculated "SIZE_FORMAT,
+                                 r->bottom(), r->end(),
+                                 r->max_live_bytes(),
+                                 not_dead_yet_cl.live_bytes());
+          _failures = true;
+        }
+      }
     }
-    return false;
+    return false; // stop the region iteration if we hit a failure
   }
 };
 
 class VerifyRootsClosure: public OopsInGenClosure {
 private:
   G1CollectedHeap* _g1h;
-  bool             _failures;
   bool             _use_prev_marking;
+  bool             _failures;
 public:
   // use_prev_marking == true  -> use "prev" marking information,
   // use_prev_marking == false -> use "next" marking information
   VerifyRootsClosure(bool use_prev_marking) :
     _g1h(G1CollectedHeap::heap()),
-    _failures(false),
-    _use_prev_marking(use_prev_marking) { }
+    _use_prev_marking(use_prev_marking),
+    _failures(false) { }
 
   bool failures() { return _failures; }
 
@@ -2253,7 +2271,7 @@ public:
       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
       if (_g1h->is_obj_dead_cond(obj, _use_prev_marking)) {
         gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
-                               "points to dead obj "PTR_FORMAT, p, (void*) obj);
+                              "points to dead obj "PTR_FORMAT, p, (void*) obj);
         obj->print_on(gclog_or_tty);
         _failures = true;
       }
@@ -2271,6 +2289,7 @@ private:
   G1CollectedHeap* _g1h;
   bool _allow_dirty;
   bool _use_prev_marking;
+  bool _failures;
 
 public:
   // use_prev_marking == true  -> use "prev" marking information,
@@ -2280,13 +2299,21 @@ public:
     AbstractGangTask("Parallel verify task"),
     _g1h(g1h),
     _allow_dirty(allow_dirty),
-    _use_prev_marking(use_prev_marking) { }
+    _use_prev_marking(use_prev_marking),
+    _failures(false) { }
+
+  bool failures() {
+    return _failures;
+  }
 
   void work(int worker_i) {
     HandleMark hm;
     VerifyRegionClosure blk(_allow_dirty, true, _use_prev_marking);
     _g1h->heap_region_par_iterate_chunked(&blk, worker_i,
                                           HeapRegion::ParVerifyClaimValue);
+    if (blk.failures()) {
+      _failures = true;
+    }
   }
 };
 
@@ -2307,6 +2334,7 @@ void G1CollectedHeap::verify(bool allow_dirty,
                          &rootsCl,
                          &blobsCl,
                          &rootsCl);
+    bool failures = rootsCl.failures();
     rem_set()->invalidate(perm_gen()->used_region(), false);
     if (!silent) { gclog_or_tty->print("heapRegions "); }
     if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
@@ -2318,6 +2346,9 @@ void G1CollectedHeap::verify(bool allow_dirty,
       set_par_threads(n_workers);
       workers()->run_task(&task);
       set_par_threads(0);
+      if (task.failures()) {
+        failures = true;
+      }
 
       assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
              "sanity check");
@@ -2329,10 +2360,23 @@ void G1CollectedHeap::verify(bool allow_dirty,
     } else {
       VerifyRegionClosure blk(allow_dirty, false, use_prev_marking);
       _hrs->iterate(&blk);
+      if (blk.failures()) {
+        failures = true;
+      }
     }
     if (!silent) gclog_or_tty->print("remset ");
     rem_set()->verify();
-    guarantee(!rootsCl.failures(), "should not have had failures");
+
+    if (failures) {
+      gclog_or_tty->print_cr("Heap:");
+      print_on(gclog_or_tty, true /* extended */);
+      gclog_or_tty->print_cr("");
+      if (VerifyDuringGC && G1VerifyConcMarkPrintReachable) {
+        concurrent_mark()->print_prev_bitmap_reachable();
+      }
+      gclog_or_tty->flush();
+    }
+    guarantee(!failures, "there should not have been any failures");
   } else {
     if (!silent) gclog_or_tty->print("(SKIPPING roots, heapRegions, remset) ");
   }
@@ -2374,6 +2418,7 @@ void G1CollectedHeap::print_on(outputStream* st, bool extended) const {
   st->cr();
   perm()->as_gen()->print_on(st);
   if (extended) {
+    st->cr();
     print_on_extended(st);
   }
 }

src/share/vm/gc_implementation/g1/heapRegion.cpp

@@ -722,12 +722,13 @@ void HeapRegion::print_on(outputStream* st) const {
     st->print(" F");
   else
     st->print("  ");
-  st->print(" %d", _gc_time_stamp);
+  st->print(" %5d", _gc_time_stamp);
   G1OffsetTableContigSpace::print_on(st);
 }
 
 void HeapRegion::verify(bool allow_dirty) const {
-  verify(allow_dirty, /* use_prev_marking */ true);
+  bool dummy = false;
+  verify(allow_dirty, /* use_prev_marking */ true, /* failures */ &dummy);
 }
 
 #define OBJ_SAMPLE_INTERVAL 0
@@ -736,8 +737,11 @@ void HeapRegion::verify(bool allow_dirty) const {
 // This really ought to be commoned up into OffsetTableContigSpace somehow.
 // We would need a mechanism to make that code skip dead objects.
 
-void HeapRegion::verify(bool allow_dirty, bool use_prev_marking) const {
+void HeapRegion::verify(bool allow_dirty,
+                        bool use_prev_marking,
+                        bool* failures) const {
   G1CollectedHeap* g1 = G1CollectedHeap::heap();
+  *failures = false;
   HeapWord* p = bottom();
   HeapWord* prev_p = NULL;
   int objs = 0;
@@ -746,8 +750,14 @@ void HeapRegion::verify(bool allow_dirty, bool use_prev_marking) const {
   while (p < top()) {
     size_t size = oop(p)->size();
     if (blocks == BLOCK_SAMPLE_INTERVAL) {
-      guarantee(p == block_start_const(p + (size/2)),
-                "check offset computation");
+      HeapWord* res = block_start_const(p + (size/2));
+      if (p != res) {
+        gclog_or_tty->print_cr("offset computation 1 for "PTR_FORMAT" and "
+                               SIZE_FORMAT" returned "PTR_FORMAT,
+                               p, size, res);
+        *failures = true;
+        return;
+      }
       blocks = 0;
     } else {
       blocks++;
@@ -755,11 +765,34 @@ void HeapRegion::verify(bool allow_dirty, bool use_prev_marking) const {
     if (objs == OBJ_SAMPLE_INTERVAL) {
       oop obj = oop(p);
       if (!g1->is_obj_dead_cond(obj, this, use_prev_marking)) {
-        obj->verify();
-        vl_cl.set_containing_obj(obj);
-        obj->oop_iterate(&vl_cl);
-        if (G1MaxVerifyFailures >= 0
-            && vl_cl.n_failures() >= G1MaxVerifyFailures) break;
+        if (obj->is_oop()) {
+          klassOop klass = obj->klass();
+          if (!klass->is_perm()) {
+            gclog_or_tty->print_cr("klass "PTR_FORMAT" of object "PTR_FORMAT" "
+                                   "not in perm", klass, obj);
+            *failures = true;
+            return;
+          } else if (!klass->is_klass()) {
+            gclog_or_tty->print_cr("klass "PTR_FORMAT" of object "PTR_FORMAT" "
+                                   "not a klass", klass, obj);
+            *failures = true;
+            return;
+          } else {
+            vl_cl.set_containing_obj(obj);
+            obj->oop_iterate(&vl_cl);
+            if (vl_cl.failures()) {
+              *failures = true;
+            }
+            if (G1MaxVerifyFailures >= 0 &&
+                vl_cl.n_failures() >= G1MaxVerifyFailures) {
+              return;
+            }
+          }
+        } else {
+          gclog_or_tty->print_cr(PTR_FORMAT" no an oop", obj);
+          *failures = true;
+          return;
+        }
       }
       objs = 0;
     } else {
@@ -771,21 +804,22 @@ void HeapRegion::verify(bool allow_dirty, bool use_prev_marking) const {
   HeapWord* rend = end();
   HeapWord* rtop = top();
   if (rtop < rend) {
-    guarantee(block_start_const(rtop + (rend - rtop) / 2) == rtop,
-              "check offset computation");
-  }
-  if (vl_cl.failures()) {
-    gclog_or_tty->print_cr("Heap:");
-    G1CollectedHeap::heap()->print_on(gclog_or_tty, true /* extended */);
-    gclog_or_tty->print_cr("");
+    HeapWord* res = block_start_const(rtop + (rend - rtop) / 2);
+    if (res != rtop) {
+        gclog_or_tty->print_cr("offset computation 2 for "PTR_FORMAT" and "
+                               PTR_FORMAT" returned "PTR_FORMAT,
+                               rtop, rend, res);
+        *failures = true;
+        return;
+    }
   }
-  if (VerifyDuringGC &&
-      G1VerifyConcMarkPrintReachable &&
-      vl_cl.failures()) {
-    g1->concurrent_mark()->print_prev_bitmap_reachable();
+
+  if (p != top()) {
+    gclog_or_tty->print_cr("end of last object "PTR_FORMAT" "
+                           "does not match top "PTR_FORMAT, p, top());
+    *failures = true;
+    return;
   }
-  guarantee(!vl_cl.failures(), "region verification failed");
-  guarantee(p == top(), "end of last object must match end of space");
 }
 
 // G1OffsetTableContigSpace code; copied from space.cpp.  Hope this can go

src/share/vm/gc_implementation/g1/heapRegion.hpp

@@ -798,7 +798,7 @@ class HeapRegion: public G1OffsetTableContigSpace {
   // use_prev_marking == true. Currently, there is only one case where
   // this is called with use_prev_marking == false, which is to verify
   // the "next" marking information at the end of remark.
-  void verify(bool allow_dirty, bool use_prev_marking) const;
+  void verify(bool allow_dirty, bool use_prev_marking, bool *failures) const;
 
   // Override; it uses the "prev" marking information
   virtual void verify(bool allow_dirty) const;