Use spsc_q to process PRACH jobs

Use two queues for PRACH processing:

- prach_ru_queue: pass jobs from TX thread (scheduler) to RU thread. For
  split 8, the RU thread itself handles PRACH processing; for split 7.2,
  it is the library that is responsible for handling PRACH messages (see
  oran_fh_if4p5_south_in())
- prach_l1rx_queue: after jobs have been handled in RU thread, use this
  queue to pass jobs to the RX thread. There, preamble detection is
  performed, and RACH.indication FAPI messages are filled if a preamble
  has been detected.

Together, these queues replace a linear search in a global array that
has been modified by three threads at the same time. The design ensures
that access now is thread-safe, and with less overhead.

Signed-off-by: Robert Schmidt <robert.schmidt@openairinterface.org>

executables/nr-ru.c

@@ -15,6 +15,7 @@
 #include "common/utils/nr/nr_common.h"
 #include "common/utils/assertions.h"
 #include "common/utils/system.h"
+#include "common/utils/fsn.h"
 #include "common/ran_context.h"
 
 #include "radio/COMMON/common_lib.h"
@@ -980,11 +981,16 @@ void *ru_thread(void *param)
                      proc->tti_rx * gNB->frame_parms.samples_per_slot_wCP);
 
         // Do PRACH RU processing
-        prach_item_t *p =
-            find_nr_prach(&gNB->prach_list, proc->frame_rx, proc->tti_rx, gNB->frame_parms.nb_antennas_rx, NR_SEARCH_EXIST);
-        if (p) {
+        fsn_t now = {.f = proc->frame_rx, .s = proc->tti_rx, .mu = fp->numerology_index};
+        prach_item_t p;
+        while (get_next_nr_prach(&gNB->prach_ru_queue, &now, &p)) {
           // need to extract RACH data for later processing by rx_nr_prach()
-          rx_nr_prach_ru(p, ru->common.rxdata, ru->nr_frame_parms, ru->N_TA_offset);
+          rx_nr_prach_ru(&p, ru->common.rxdata, ru->nr_frame_parms, ru->N_TA_offset);
+          bool success = spsc_q_put(&gNB->prach_l1rx_queue, &p, sizeof(p));
+          // assume prach_l1rx_queue never full: prach_ru_queue filled at
+          // constant pace, but prach_l1rx_queue emptied as fast as possible,
+          // see rx_func()
+          DevAssert(success);
         } // end if (prach_id >= 0)
       } // end if (ru->feprx)
     } // end if (slot_type == NR_UPLINK_SLOT || slot_type == NR_MIXED_SLOT) {