ue: store new EARFCN in the foreground of cell_select to avoid race conditions with the other cmd_worker

srsue/hdr/phy/phy.h

@@ -190,6 +190,9 @@ private:
   // Tracks the current selected cell (last call to cell_select)
   srsran_cell_t selected_cell = {};
 
+  // Tracks the current selected EARFCN (last call to cell_select)
+  uint32_t selected_earfcn = 0;
+
   static void set_default_args(phy_args_t& args);
   bool        check_args(const phy_args_t& args);
 };

srsue/src/phy/phy.cc

@@ -244,8 +244,7 @@ void phy::set_cells_to_meas(uint32_t earfcn, const std::set<uint32_t>& pci)
   // measurements to avoid a concurrency issue
   cmd_worker.add_cmd([this, earfcn, pci]() {
     // Check if the EARFCN matches with serving cell
-    uint32_t pcell_earfcn = 0;
-    sfsync.get_current_cell(nullptr, &pcell_earfcn);
+    uint32_t pcell_earfcn = selected_earfcn;
     bool available = (pcell_earfcn == earfcn);
 
     // Find if there is secondary serving cell configured with the specified EARFCN
@@ -303,6 +302,10 @@ bool phy::cell_select(phy_cell_t cell)
     // Indicate workers that cell selection is in progress
     common.cell_is_selecting = true;
 
+    // Update EARCN before starting the background task to make sure is taken into account when finding carriers to
+    // measure inter-frequency neighbours (see set_cells_to_meas)
+    selected_earfcn = cell.earfcn;
+
     cmd_worker_cell.add_cmd([this, cell]() {
       // Wait SYNC transitions to IDLE
       sfsync.wait_idle();