From 09354db1434859a31a3c81abebcc4018d42f2715 Mon Sep 17 00:00:00 2001
From: Jisi Liu <jisi.liu@gmail.com>
Date: Tue, 18 Jul 2017 15:38:30 -0700
Subject: Merge from Google internal for 3.4 release

---
 src/google/protobuf/dynamic_message.cc | 36 +++++++++++++++++++++++++++-------
 1 file changed, 29 insertions(+), 7 deletions(-)

(limited to 'src/google/protobuf/dynamic_message.cc')

diff --git a/src/google/protobuf/dynamic_message.cc b/src/google/protobuf/dynamic_message.cc
index ee8113e3..cdd43243 100644
--- a/src/google/protobuf/dynamic_message.cc
+++ b/src/google/protobuf/dynamic_message.cc
@@ -250,6 +250,10 @@ class DynamicMessage : public Message {
   };
 
   DynamicMessage(const TypeInfo* type_info);
+
+  // This should only be used by GetPrototypeNoLock() to avoid dead lock.
+  DynamicMessage(const TypeInfo* type_info, bool lock_factory);
+
   ~DynamicMessage();
 
   // Called on the prototype after construction to initialize message fields.
@@ -280,7 +284,8 @@ class DynamicMessage : public Message {
  private:
   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(DynamicMessage);
   DynamicMessage(const TypeInfo* type_info, ::google::protobuf::Arena* arena);
-  void SharedCtor();
+
+  void SharedCtor(bool lock_factory);
 
   inline bool is_prototype() const {
     return type_info_->prototype == this ||
@@ -304,17 +309,22 @@ class DynamicMessage : public Message {
 DynamicMessage::DynamicMessage(const TypeInfo* type_info)
   : type_info_(type_info),
     cached_byte_size_(0) {
-  SharedCtor();
+  SharedCtor(true);
 }
 
 DynamicMessage::DynamicMessage(const TypeInfo* type_info,
                                ::google::protobuf::Arena* arena)
   : type_info_(type_info),
     cached_byte_size_(0) {
-  SharedCtor();
+  SharedCtor(true);
+}
+
+DynamicMessage::DynamicMessage(const TypeInfo* type_info, bool lock_factory)
+    : type_info_(type_info), cached_byte_size_(0) {
+  SharedCtor(lock_factory);
 }
 
-void DynamicMessage::SharedCtor() {
+void DynamicMessage::SharedCtor(bool lock_factory) {
   // We need to call constructors for various fields manually and set
   // default values where appropriate.  We use placement new to call
   // constructors.  If you haven't heard of placement new, I suggest Googling
@@ -398,8 +408,17 @@ void DynamicMessage::SharedCtor() {
           new(field_ptr) Message*(NULL);
         } else {
           if (IsMapFieldInApi(field)) {
-            new (field_ptr) DynamicMapField(
-                type_info_->factory->GetPrototypeNoLock(field->message_type()));
+            // We need to lock in most cases to avoid data racing. Only not lock
+            // when the constructor is called inside GetPrototype(), in which
+            // case we have already locked the factory.
+            if (lock_factory) {
+              new (field_ptr) DynamicMapField(
+                  type_info_->factory->GetPrototype(field->message_type()));
+            } else {
+              new (field_ptr)
+                  DynamicMapField(type_info_->factory->GetPrototypeNoLock(
+                      field->message_type()));
+            }
           } else {
             new (field_ptr) RepeatedPtrField<Message>();
           }
@@ -751,7 +770,10 @@ const Message* DynamicMessageFactory::GetPrototypeNoLock(
   // map). To break the cyclic dependency, we have to assgin the address of
   // prototype into type_info first.
   type_info->prototype = static_cast<DynamicMessage*>(base);
-  DynamicMessage* prototype = new(base) DynamicMessage(type_info);
+
+  // We have already locked the factory so we should not lock in the constructor
+  // of dynamic message to avoid dead lock.
+  DynamicMessage* prototype = new (base) DynamicMessage(type_info, false);
 
   if (type->oneof_decl_count() > 0 || num_weak_fields > 0) {
     // Construct default oneof instance.
-- 
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