rlc: protect access to tx_enabled

lib/include/srsran/rlc/rlc_am_lte.h

@@ -387,6 +387,8 @@ private:
     void set_bsr_callback(bsr_callback_t callback);
 
   private:
+    void stop_nolock();
+
     int  build_status_pdu(uint8_t* payload, uint32_t nof_bytes);
     int  build_retx_pdu(uint8_t* payload, uint32_t nof_bytes);
     int  build_segment(uint8_t* payload, uint32_t nof_bytes, rlc_amd_retx_t retx);

lib/src/rlc/rlc_am_lte.cc

@@ -343,7 +343,11 @@ bool rlc_am_lte::rlc_am_lte_tx::configure(const rlc_config_t& cfg_)
 void rlc_am_lte::rlc_am_lte_tx::stop()
 {
   std::lock_guard<std::mutex> lock(mutex);
+  stop_nolock();
+}
 
+void rlc_am_lte::rlc_am_lte_tx::stop_nolock()
+{
   empty_queue_nolock();
 
   tx_enabled = false;
@@ -396,7 +400,8 @@ void rlc_am_lte::rlc_am_lte_tx::empty_queue_nolock()
 
 void rlc_am_lte::rlc_am_lte_tx::reestablish()
 {
-  stop();
+  std::lock_guard<std::mutex> lock(mutex);
+  stop_nolock();
   tx_enabled = true;
 }