Fix deadlock issue

RawDevice would deadlock in some situations because I/O occured while
the listener was turning on. This also seems to have fixed logid
sometimes not detecting devices on receivers.

src/logid/backend/dj/Receiver.cpp

@@ -325,9 +325,7 @@ void Receiver::listen()
 {
     if(!_raw_device->isListening())
         ///TODO: Kill RawDevice?
-        thread::spawn({[raw=this->_raw_device]() {
-            raw->listen();
-        }});
+        _raw_device->listenAsync();
 
     if(_raw_device->eventHandlers().find("RECV_HIDPP") ==
         _raw_device->eventHandlers().end()) {

src/logid/backend/hidpp/Device.cpp

@@ -200,9 +200,7 @@ uint16_t Device::pid() const
 void Device::listen()
 {
     if(!_raw_device->isListening())
-        thread::spawn({[raw=this->_raw_device]() {
-            raw->listen();
-        }});
+        _raw_device->listenAsync();
 
     // Pass all HID++ events with device index to this device.
     auto handler = std::make_shared<raw::RawEventHandler>();

src/logid/backend/raw/RawDevice.cpp

@@ -23,6 +23,7 @@
 #include "../../util/log.h"
 #include "../hidpp/Report.h"
 #include "../../Configuration.h"
+#include "../../util/thread.h"
 
 #include <string>
 #include <system_error>
@@ -327,8 +328,8 @@ void RawDevice::interruptRead()
 void RawDevice::listen()
 {
     std::lock_guard<std::mutex> lock(_listening);
-
     _continue_listen = true;
+    _listen_condition.notify_all();
     while(_continue_listen) {
         while(!_io_queue.empty()) {
             auto task = _io_queue.front();
@@ -351,6 +352,18 @@ void RawDevice::listen()
     _continue_listen = false;
 }
 
+void RawDevice::listenAsync()
+{
+    std::mutex listen_check;
+    std::unique_lock<std::mutex> check_lock(listen_check);
+    thread::spawn({[this]() { listen(); }});
+
+    // Block until RawDevice is listening
+    _listen_condition.wait(check_lock, [this](){
+        return (bool)_continue_listen;
+    });
+}
+
 void RawDevice::stopListener()
 {
     _continue_listen = false;

src/logid/backend/raw/RawDevice.h

@@ -54,6 +54,7 @@ namespace raw
         void interruptRead();
 
         void listen();
+        void listenAsync();
         void stopListener();
         bool isListening();
 
@@ -74,6 +75,7 @@ namespace raw
         std::vector<uint8_t> rdesc;
 
         std::atomic<bool> _continue_listen;
+        std::condition_variable _listen_condition;
 
         std::map<std::string, std::shared_ptr<RawEventHandler>>
             _event_handlers;