Update VirtualSocketServer locking to match documentation.

Add GUARDED_BY annotation on members claimed to be protected by the
lock, and add missing lock operations. Also mark a few members const.

Bug: webrtc:11567, webrtc:2079
Change-Id: I8f12ca7627df0c24e07fa2ae24a387c6a0ed76cf
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/208224
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34340}

rtc_base/virtual_socket_server.cc

@@ -164,6 +164,8 @@ int VirtualSocket::Close() {
   }
 
   if (SOCK_STREAM == type_) {
+    CritScope cs(&crit_);
+
     // Cancel pending sockets
     if (listen_queue_) {
       while (!listen_queue_->empty()) {
@@ -231,6 +233,8 @@ int VirtualSocket::RecvFrom(void* pv,
   if (timestamp) {
     *timestamp = -1;
   }
+
+  CritScope cs(&crit_);
   // If we don't have a packet, then either error or wait for one to arrive.
   if (recv_buffer_.empty()) {
     if (async_) {
@@ -273,6 +277,7 @@ int VirtualSocket::RecvFrom(void* pv,
 }
 
 int VirtualSocket::Listen(int backlog) {
+  CritScope cs(&crit_);
   RTC_DCHECK(SOCK_STREAM == type_);
   RTC_DCHECK(CS_CLOSED == state_);
   if (local_addr_.IsNil()) {
@@ -286,6 +291,7 @@ int VirtualSocket::Listen(int backlog) {
 }
 
 VirtualSocket* VirtualSocket::Accept(SocketAddress* paddr) {
+  CritScope cs(&crit_);
   if (nullptr == listen_queue_) {
     error_ = EINVAL;
     return nullptr;
@@ -341,48 +347,53 @@ int VirtualSocket::SetOption(Option opt, int value) {
 }
 
 void VirtualSocket::OnMessage(Message* pmsg) {
+  bool signal_read_event = false;
+  bool signal_close_event = false;
+  int error_to_signal = 0;
+  {
+    CritScope cs(&crit_);
     if (pmsg->message_id == MSG_ID_PACKET) {
       RTC_DCHECK(nullptr != pmsg->pdata);
       Packet* packet = static_cast<Packet*>(pmsg->pdata);
 
       recv_buffer_.push_back(packet);
-
+      signal_read_event = async_;
-    if (async_) {
-      SignalReadEvent(this);
-    }
     } else if (pmsg->message_id == MSG_ID_CONNECT) {
       RTC_DCHECK(nullptr != pmsg->pdata);
       MessageAddress* data = static_cast<MessageAddress*>(pmsg->pdata);
       if (listen_queue_ != nullptr) {
         listen_queue_->push_back(data->addr);
-      if (async_) {
+        signal_read_event = async_;
-        SignalReadEvent(this);
-      }
       } else if ((SOCK_STREAM == type_) && (CS_CONNECTING == state_)) {
         CompleteConnect(data->addr, true);
       } else {
-      RTC_LOG(LS_VERBOSE) << "Socket at " << local_addr_.ToString()
+        RTC_LOG(LS_VERBOSE)
-                          << " is not listening";
+            << "Socket at " << local_addr_.ToString() << " is not listening";
         server_->Disconnect(data->addr);
       }
       delete data;
     } else if (pmsg->message_id == MSG_ID_DISCONNECT) {
       RTC_DCHECK(SOCK_STREAM == type_);
       if (CS_CLOSED != state_) {
-      int error = (CS_CONNECTING == state_) ? ECONNREFUSED : 0;
+        error_to_signal = (CS_CONNECTING == state_) ? ECONNREFUSED : 0;
         state_ = CS_CLOSED;
         remote_addr_.Clear();
-      if (async_) {
+        signal_close_event = async_;
-        SignalCloseEvent(this, error);
-      }
       }
     } else if (pmsg->message_id == MSG_ID_SIGNALREADEVENT) {
-    if (!recv_buffer_.empty()) {
+      signal_read_event = !recv_buffer_.empty();
-      SignalReadEvent(this);
-    }
     } else {
       RTC_NOTREACHED();
     }
+  }
+  // Signal events without holding `crit_`, to avoid lock order inversion with
+  // sigslot locks.
+  if (signal_read_event) {
+    SignalReadEvent(this);
+  }
+  if (signal_close_event) {
+    SignalCloseEvent(this, error_to_signal);
+  }
 }
 
 int VirtualSocket::InitiateConnect(const SocketAddress& addr, bool use_delay) {

rtc_base/virtual_socket_server.h

@@ -400,16 +400,16 @@ class VirtualSocket : public AsyncSocket,
 
   void OnSocketServerReadyToSend();
 
-  VirtualSocketServer* server_;
+  VirtualSocketServer* const server_;
-  int type_;
+  const int type_;
-  bool async_;
+  const bool async_;
   ConnState state_;
   int error_;
   SocketAddress local_addr_;
   SocketAddress remote_addr_;
 
   // Pending sockets which can be Accepted
-  ListenQueue* listen_queue_;
+  ListenQueue* listen_queue_ RTC_GUARDED_BY(crit_) RTC_PT_GUARDED_BY(crit_);
 
   // Data which tcp has buffered for sending
   SendBuffer send_buffer_;
@@ -417,7 +417,7 @@ class VirtualSocket : public AsyncSocket,
   // Set back to true when the socket can send again.
   bool ready_to_send_ = true;
 
-  // Critical section to protect the recv_buffer and queue_
+  // Critical section to protect the recv_buffer and listen_queue_
   RecursiveCriticalSection crit_;
 
   // Network model that enforces bandwidth and capacity constraints
@@ -428,7 +428,7 @@ class VirtualSocket : public AsyncSocket,
   int64_t last_delivery_time_ = 0;
 
   // Data which has been received from the network
-  RecvBuffer recv_buffer_;
+  RecvBuffer recv_buffer_ RTC_GUARDED_BY(crit_);
   // The amount of data which is in flight or in recv_buffer_
   size_t recv_buffer_size_;