prach: protect configuration and state getters with mutex

purely TSAN with unit-test based approach that protects
the state getters and configuration routines with a mutex

srsue/hdr/phy/prach.h

@@ -18,6 +18,7 @@
 #include "srsran/srslog/srslog.h"
 #include "srsran/srsran.h"
 #include <bitset>
+#include <mutex>
 
 namespace srsue {
 
@@ -70,6 +71,7 @@ private:
   bool                                                 mem_initiated    = false;
   bool                                                 cell_initiated   = false;
   std::bitset<max_fs * max_preambles>                  buffer_bitmask;
+  mutable std::mutex                                   mutex;
 };
 
 } // namespace srsue

srsue/src/phy/prach.cc

@@ -83,6 +83,8 @@ void prach::stop()
 
 bool prach::set_cell(srsran_cell_t cell_, srsran_prach_cfg_t prach_cfg)
 {
+  std::lock_guard<std::mutex> lock(mutex);
+
   if (!mem_initiated) {
     ERROR("PRACH: Error must call init() first");
     return false;
@@ -147,6 +149,7 @@ bool prach::generate_buffer(uint32_t f_idx)
 
 bool prach::prepare_to_send(uint32_t preamble_idx_, int allowed_subframe_, float target_power_dbm_)
 {
+  std::lock_guard<std::mutex> lock(mutex);
   if (preamble_idx_ >= max_preambles) {
     Error("PRACH: Invalid preamble %d", preamble_idx_);
     return false;
@@ -162,7 +165,11 @@ bool prach::prepare_to_send(uint32_t preamble_idx_, int allowed_subframe_, float
 
 bool prach::is_pending() const
 {
-  return cell_initiated && preamble_idx >= 0 && unsigned(preamble_idx) < max_preambles;
+  std::unique_lock<std::mutex> lock(mutex, std::try_to_lock);
+  if (lock.owns_lock()) {
+    return cell_initiated && preamble_idx >= 0 && unsigned(preamble_idx) < max_preambles;
+  }
+  return false;
 }
 
 bool prach::is_ready_to_send(uint32_t current_tti_, uint32_t current_pci)