ART: Add templated VisitObjects

Add templated versions of VisitObjects that accept visitors. This
allows to use more modern lambdas.

Test: m
Change-Id: I71a7f59bcae02090b9493bf8b477bb8b6ba649de

1 files changed, 169 insertions, 0 deletions

diff --git a/runtime/gc/heap-visit-objects-inl.h b/runtime/gc/heap-visit-objects-inl.h
new file mode 100644
index 0000000000..b6ccb277cd
--- /dev/null
+++ b/runtime/gc/heap-visit-objects-inl.h
@@ -0,0 +1,169 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ART_RUNTIME_GC_HEAP_VISIT_OBJECTS_INL_H_
+#define ART_RUNTIME_GC_HEAP_VISIT_OBJECTS_INL_H_
+
+#include "heap.h"
+
+#include "base/mutex-inl.h"
+#include "gc/accounting/heap_bitmap-inl.h"
+#include "gc/space/bump_pointer_space-walk-inl.h"
+#include "gc/space/region_space-inl.h"
+#include "mirror/object-inl.h"
+#include "obj_ptr-inl.h"
+#include "scoped_thread_state_change-inl.h"
+#include "thread-current-inl.h"
+#include "thread_list.h"
+
+namespace art {
+namespace gc {
+
+// Visit objects when threads aren't suspended. If concurrent moving
+// GC, disable moving GC and suspend threads and then visit objects.
+template <typename Visitor>
+inline void Heap::VisitObjects(Visitor&& visitor) {
+  Thread* self = Thread::Current();
+  Locks::mutator_lock_->AssertSharedHeld(self);
+  DCHECK(!Locks::mutator_lock_->IsExclusiveHeld(self)) << "Call VisitObjectsPaused() instead";
+  if (IsGcConcurrentAndMoving()) {
+    // Concurrent moving GC. Just suspending threads isn't sufficient
+    // because a collection isn't one big pause and we could suspend
+    // threads in the middle (between phases) of a concurrent moving
+    // collection where it's not easily known which objects are alive
+    // (both the region space and the non-moving space) or which
+    // copies of objects to visit, and the to-space invariant could be
+    // easily broken. Visit objects while GC isn't running by using
+    // IncrementDisableMovingGC() and threads are suspended.
+    IncrementDisableMovingGC(self);
+    {
+      ScopedThreadSuspension sts(self, kWaitingForVisitObjects);
+      ScopedSuspendAll ssa(__FUNCTION__);
+      VisitObjectsInternalRegionSpace(visitor);
+      VisitObjectsInternal(visitor);
+    }
+    DecrementDisableMovingGC(self);
+  } else {
+    // Since concurrent moving GC has thread suspension, also poison ObjPtr the normal case to
+    // catch bugs.
+    self->PoisonObjectPointers();
+    // GCs can move objects, so don't allow this.
+    ScopedAssertNoThreadSuspension ants("Visiting objects");
+    DCHECK(region_space_ == nullptr);
+    VisitObjectsInternal(visitor);
+    self->PoisonObjectPointers();
+  }
+}
+
+template <typename Visitor>
+inline void Heap::VisitObjectsPaused(Visitor&& visitor) {
+  Thread* self = Thread::Current();
+  Locks::mutator_lock_->AssertExclusiveHeld(self);
+  VisitObjectsInternalRegionSpace(visitor);
+  VisitObjectsInternal(visitor);
+}
+
+// Visit objects in the region spaces.
+template <typename Visitor>
+inline void Heap::VisitObjectsInternalRegionSpace(Visitor&& visitor) {
+  Thread* self = Thread::Current();
+  Locks::mutator_lock_->AssertExclusiveHeld(self);
+  if (region_space_ != nullptr) {
+    DCHECK(IsGcConcurrentAndMoving());
+    if (!zygote_creation_lock_.IsExclusiveHeld(self)) {
+      // Exclude the pre-zygote fork time where the semi-space collector
+      // calls VerifyHeapReferences() as part of the zygote compaction
+      // which then would call here without the moving GC disabled,
+      // which is fine.
+      bool is_thread_running_gc = false;
+      if (kIsDebugBuild) {
+        MutexLock mu(self, *gc_complete_lock_);
+        is_thread_running_gc = self == thread_running_gc_;
+      }
+      // If we are not the thread running the GC on in a GC exclusive region, then moving GC
+      // must be disabled.
+      DCHECK(is_thread_running_gc || IsMovingGCDisabled(self));
+    }
+    region_space_->Walk(visitor);
+  }
+}
+
+// Visit objects in the other spaces.
+template <typename Visitor>
+inline void Heap::VisitObjectsInternal(Visitor&& visitor) {
+  if (bump_pointer_space_ != nullptr) {
+    // Visit objects in bump pointer space.
+    bump_pointer_space_->Walk(visitor);
+  }
+  // TODO: Switch to standard begin and end to use ranged a based loop.
+  for (auto* it = allocation_stack_->Begin(), *end = allocation_stack_->End(); it < end; ++it) {
+    mirror::Object* const obj = it->AsMirrorPtr();
+
+    mirror::Class* kls = nullptr;
+    if (obj != nullptr && (kls = obj->GetClass()) != nullptr) {
+      // Below invariant is safe regardless of what space the Object is in.
+      // For speed reasons, only perform it when Rosalloc could possibly be used.
+      // (Disabled for read barriers because it never uses Rosalloc).
+      // (See the DCHECK in RosAllocSpace constructor).
+      if (!kUseReadBarrier) {
+        // Rosalloc has a race in allocation. Objects can be written into the allocation
+        // stack before their header writes are visible to this thread.
+        // See b/28790624 for more details.
+        //
+        // obj.class will either be pointing to a valid Class*, or it will point
+        // to a rosalloc free buffer.
+        //
+        // If it's pointing to a valid Class* then that Class's Class will be the
+        // ClassClass (whose Class is itself).
+        //
+        // A rosalloc free buffer will point to another rosalloc free buffer
+        // (or to null), and never to itself.
+        //
+        // Either way dereferencing while its not-null is safe because it will
+        // always point to another valid pointer or to null.
+        mirror::Class* klsClass = kls->GetClass();
+
+        if (klsClass == nullptr) {
+          continue;
+        } else if (klsClass->GetClass() != klsClass) {
+          continue;
+        }
+      } else {
+        // Ensure the invariant is not broken for non-rosalloc cases.
+        DCHECK(Heap::rosalloc_space_ == nullptr)
+            << "unexpected rosalloc with read barriers";
+        DCHECK(kls->GetClass() != nullptr)
+            << "invalid object: class does not have a class";
+        DCHECK_EQ(kls->GetClass()->GetClass(), kls->GetClass())
+            << "invalid object: class's class is not ClassClass";
+      }
+
+      // Avoid the race condition caused by the object not yet being written into the allocation
+      // stack or the class not yet being written in the object. Or, if
+      // kUseThreadLocalAllocationStack, there can be nulls on the allocation stack.
+      visitor(obj);
+    }
+  }
+  {
+    ReaderMutexLock mu(Thread::Current(), *Locks::heap_bitmap_lock_);
+    GetLiveBitmap()->Visit<Visitor>(visitor);
+  }
+}
+
+}  // namespace gc
+}  // namespace art
+
+#endif  // ART_RUNTIME_GC_HEAP_VISIT_OBJECTS_INL_H_