From 95c8fa468ac577f17924a18491f3712529b750fe Mon Sep 17 00:00:00 2001
From: andrewse <andrew.sergeev@adtran.com>
Date: Thu, 4 Dec 2025 11:28:31 +0000
Subject: [PATCH] fhi_72: Track delay processing via atomic variable

Add xran_queue_length atomic variable to count the number of messages in
oran_sync_fifo (as notifiedFIFO_t does not do this). Use this to
tolerate some double messages (e.g. excessive processing delay), but
start to skip if messages accumulate.

Prior to this change, "Detected double sync message" was printed each
time there was more than one message, which reflected the previous
behavior when using polling, but the gNB might catch up if it is only
once. The new logic ensure that we don't skip individual slots but do so
once messages start to accumulate.
---
 radio/fhi_72/oaioran.c | 34 +++++++++++++++++++++++-----------
 1 file changed, 23 insertions(+), 11 deletions(-)

diff --git a/radio/fhi_72/oaioran.c b/radio/fhi_72/oaioran.c
index 31c754738d..cea202346c 100644
--- a/radio/fhi_72/oaioran.c
+++ b/radio/fhi_72/oaioran.c
@@ -22,6 +22,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>
+#include <stdatomic.h>
 #include "xran_fh_o_du.h"
 #include "xran_compression.h"
 #include "armral_bfp_compression.h"
@@ -56,6 +57,7 @@ int xran_is_prach_slot(uint8_t PortId, uint32_t subframe_id, uint32_t slot_id);
 
 #ifndef USE_POLLING
 extern notifiedFIFO_t oran_sync_fifo;
+atomic_int xran_queue_length = 0;
 #else
 volatile oran_sync_info_t oran_sync_info = {0};
 #endif
@@ -136,6 +138,7 @@ void oai_xran_fh_rx_callback(void *pCallbackTag, xran_status_t status)
       info->sl = slot2;
       info->f = frame;
       LOG_D(HW, "Push %d.%d.%d (slot %d, subframe %d,last_slot %d)\n", frame, info->sl, slot, ru_id, subframe, last_slot);
+      atomic_fetch_add(&xran_queue_length, 1);
       pushNotifiedFIFO(&oran_sync_fifo, req);
 #else
       LOG_D(HW, "Writing %d.%d.%d (slot %d, subframe %d,last_slot %d)\n", frame, slot2, ru_id, slot, subframe, last_slot);
@@ -294,20 +297,29 @@ int xran_fh_rx_read_slot(ru_info_t *ru, int *frame, int *slot)
   struct xran_common_counters x_counters[XRAN_PORTS_NUM];
   static int outcnt = 0;
 #ifndef USE_POLLING
-  // pull next even from oran_sync_fifo
+  // pull next event from oran_sync_fifo
   notifiedFIFO_elt_t *res = pullNotifiedFIFO(&oran_sync_fifo);
-
-  notifiedFIFO_elt_t *f;
-  while ((f = pollNotifiedFIFO(&oran_sync_fifo)) != NULL) {
-    oran_sync_info_t *old_info = NotifiedFifoData(res);
-    oran_sync_info_t *new_info = NotifiedFifoData(f);
-    LOG_E(HW, "Detected double sync message %d.%d => %d.%d\n", old_info->f, old_info->sl, new_info->f, new_info->sl);
-    delNotifiedFIFO_elt(res);
-    res = f;
-  }
-
+  atomic_fetch_sub(&xran_queue_length, 1);
   oran_sync_info_t *info = NotifiedFifoData(res);
 
+#define MAX_QUEUE_LENGTH_NO_JUMP 3
+  if (xran_queue_length > 0 && xran_queue_length < MAX_QUEUE_LENGTH_NO_JUMP) {
+    LOG_D(HW, "%4d.%2d TTI processing delay detected\n", info->f, info->sl);
+  } else if (xran_queue_length >= MAX_QUEUE_LENGTH_NO_JUMP) {
+    uint32_t old_f = info->f;
+    uint32_t old_sl = info->sl;
+    // set the frame/slot info to what is in the last message
+    notifiedFIFO_elt_t *f;
+    while ((f = pollNotifiedFIFO(&oran_sync_fifo)) != NULL) {
+      atomic_fetch_sub(&xran_queue_length, 1);
+      delNotifiedFIFO_elt(res);
+      res = f;
+    }
+    info = NotifiedFifoData(res);
+    LOG_W(HW, "TTI processing delay detected, skipping %4d.%2d => %4d.%2d\n", old_f, old_sl, info->f, info->sl);
+    DevAssert(xran_queue_length == 0);
+  }
+
   *slot = info->sl;
   *frame = info->f;
   delNotifiedFIFO_elt(res);