rewrite sort_UE for UL and DL and adapt the rest to the change

The previous version did not seem to work properly with
several UEs. I too often ended up with a list 'next' where
next[i] = i, leading to an infinite loop, crashing the
processing.

The sorting functions were hard to understand and too slow
anyway (O(n*n)).

We now use qsort_r and comparison functions, that should
define the same order as the previous version.

One important point is that the "next" lists and the "head"
variable are now considered invalid before calling sort_UE.

So all the code (coming before sort_UE) that looped using those
variables has been rewritten to loop over all possible UEs and
the first instruction of the loop is to exit the loop if the UE
is not 'active'. There is room for improvement here. We will
reintroduce a list of some kind at some point. Let's first
have something that works and then optimize. Today NUMBER_OF_UE_MAX
is 16, that's not a big deal.

Consequently, the add_new_ue and rrc_mac_remove_ue have also
been rewritten, hopefully for the better.

This commit is not a basic work and may introduce some
problems.

openair2/LAYER2/MAC/eNB_scheduler.c

@@ -99,7 +99,7 @@ void eNB_dlsch_ulsch_scheduler(module_id_t module_idP,uint8_t cooperation_flag,
   int           result;
 #endif
   DCI_PDU *DCI_pdu[MAX_NUM_CCs];
-  int CC_id,i,next_i;
+  int CC_id,i; //,next_i;
   UE_list_t *UE_list=&eNB_mac_inst[module_idP].UE_list;
   rnti_t rnti;
   void         *DLSCH_dci=NULL;
@@ -133,17 +133,15 @@ void eNB_dlsch_ulsch_scheduler(module_id_t module_idP,uint8_t cooperation_flag,
   }
 
   // refresh UE list based on UEs dropped by PHY in previous subframe
-  i = UE_list->head;
+  for (i = 0; i < NUMBER_OF_UE_MAX; i++) {
+    if (UE_list->active[i] != TRUE) continue;
 
-  while (i>=0) {
     rnti = UE_RNTI(module_idP, i);
     CC_id = UE_PCCID(module_idP, i);
     if ((frameP==0)&&(subframeP==0))
       LOG_I(MAC,"UE  rnti %x : %s\n", rnti, 
 	    UE_list->UE_sched_ctrl[i].ul_out_of_sync==0 ? "in synch" : "out of sync");
 
-    next_i= UE_list->next[i];
-
     PHY_vars_eNB_g[module_idP][CC_id]->pusch_stats_bsr[i][(frameP*10)+subframeP]=-63;
     if (i==UE_list->head)
       VCD_SIGNAL_DUMPER_DUMP_VARIABLE_BY_NAME(VCD_SIGNAL_DUMPER_VARIABLES_UE0_BSR,PHY_vars_eNB_g[module_idP][CC_id]->pusch_stats_bsr[i][(frameP*10)+subframeP]); 
@@ -271,8 +269,6 @@ void eNB_dlsch_ulsch_scheduler(module_id_t module_idP,uint8_t cooperation_flag,
 	}
       }
     } // ul_failure_timer>0
-    
-    i = next_i;
   }
 
 #if defined(ENABLE_ITTI)

openair2/LAYER2/MAC/eNB_scheduler_dlsch.c

@@ -453,9 +453,11 @@ schedule_ue_spec(
   UE_sched_ctrl           *ue_sched_ctl;
   int i;
 
+#if 0
   if (UE_list->head==-1) {
     return;
   }
+#endif
 
   start_meas(&eNB->schedule_dlsch);
   VCD_SIGNAL_DUMPER_DUMP_FUNCTION_BY_NAME(VCD_SIGNAL_DUMPER_FUNCTIONS_SCHEDULE_DLSCH,VCD_FUNCTION_IN);

openair2/LAYER2/MAC/eNB_scheduler_primitives.c

@@ -107,18 +107,17 @@ DCI_PDU *get_dci_sdu(module_id_t module_idP, int CC_id,frame_t frameP, sub_frame
 int find_UE_id(module_id_t mod_idP, rnti_t rntiP)
 //------------------------------------------------------------------------------
 {
-
   int UE_id;
   UE_list_t *UE_list = &eNB_mac_inst[mod_idP].UE_list;
 
-  for (UE_id=UE_list->head; UE_id>=0; UE_id=UE_list->next[UE_id]) {
+  for (UE_id = 0; UE_id < NUMBER_OF_UE_MAX; UE_id++) {
+    if (UE_list->active[UE_id] != TRUE) continue;
     if (UE_list->UE_template[UE_PCCID(mod_idP,UE_id)][UE_id].rnti==rntiP) {
       return(UE_id);
     }
   }
 
   return(-1);
-
 }
 
 //------------------------------------------------------------------------------
@@ -235,21 +234,16 @@ void dump_ue_list(UE_list_t *listP, int ul_flag)
 int add_new_ue(module_id_t mod_idP, int cc_idP, rnti_t rntiP,int harq_pidP)
 {
   int UE_id;
-  int j;
+  int i, j;
 
   UE_list_t *UE_list = &eNB_mac_inst[mod_idP].UE_list;
 
   LOG_D(MAC,"[eNB %d, CC_id %d] Adding UE with rnti %x (next avail %d, num_UEs %d)\n",mod_idP,cc_idP,rntiP,UE_list->avail,UE_list->num_UEs);
   dump_ue_list(UE_list,0);
 
-  if (UE_list->avail>=0) {
-    UE_id = UE_list->avail;
-    AssertFatal( UE_id < NUMBER_OF_UE_MAX, "BAD UE_id %u > NUMBER_OF_UE_MAX",UE_id );
-    UE_list->avail = UE_list->next[UE_list->avail];
-    UE_list->next[UE_id] = UE_list->head;
-    UE_list->next_ul[UE_id] = UE_list->head_ul;
-    UE_list->head = UE_id;
-    UE_list->head_ul = UE_id;
+  for (i = 0; i < NUMBER_OF_UE_MAX; i++) {
+    if (UE_list->active[i] == TRUE) continue;
+    UE_id = i;
     UE_list->UE_template[cc_idP][UE_id].rnti       = rntiP;
     UE_list->UE_template[cc_idP][UE_id].configured = FALSE;
     UE_list->numactiveCCs[UE_id]                   = 1;
@@ -282,17 +276,14 @@ int add_new_ue(module_id_t mod_idP, int cc_idP, rnti_t rntiP,int harq_pidP)
 int rrc_mac_remove_ue(module_id_t mod_idP,rnti_t rntiP) 
 //------------------------------------------------------------------------------
 {
-
-  int prev,i, ret=-1;
-
-
+  int i;
   UE_list_t *UE_list = &eNB_mac_inst[mod_idP].UE_list;
   int UE_id = find_UE_id(mod_idP,rntiP);
   int pCC_id;
 
   if (UE_id == -1) {
     LOG_W(MAC,"rrc_mac_remove_ue: UE %x not found\n", rntiP);
-    mac_phy_remove_ue(mod_idP,rntiP);
+    mac_phy_remove_ue(mod_idP, rntiP);
     return 0;
   }
 
@@ -301,6 +292,9 @@ int rrc_mac_remove_ue(module_id_t mod_idP,rnti_t rntiP)
   LOG_I(MAC,"Removing UE %d from Primary CC_id %d (rnti %x)\n",UE_id,pCC_id, rntiP);
   dump_ue_list(UE_list,0);
 
+  UE_list->active[UE_id] = FALSE;
+  UE_list->num_UEs--;
+
   // clear all remaining pending transmissions
   UE_list->UE_template[pCC_id][UE_id].bsr_info[LCGID0]  = 0;
   UE_list->UE_template[pCC_id][UE_id].bsr_info[LCGID1]  = 0;
@@ -315,50 +309,6 @@ int rrc_mac_remove_ue(module_id_t mod_idP,rnti_t rntiP)
   eNB_dlsch_info[mod_idP][pCC_id][UE_id].rnti                        = NOT_A_RNTI;
   eNB_dlsch_info[mod_idP][pCC_id][UE_id].status                      = S_DL_NONE;
 
-  prev = UE_list->head;
-
-  for (i=UE_list->head; i>=0; i=UE_list->next[i]) {
-    if (i == UE_id) {
-      // link prev to next in Active list
-      if (i==UE_list->head) {
-        UE_list->head = UE_list->next[i];
-      } else {
-        UE_list->next[prev] = UE_list->next[i];
-      }
-
-      // add UE id (i)to available
-      UE_list->next[i] = UE_list->avail;
-      UE_list->avail = i;
-      UE_list->active[i] = FALSE;
-      UE_list->num_UEs--;
-      ret=0;
-      break;
-    }
-
-    prev=i;
-  }
-
-  // do the same for UL
-  prev = UE_list->head_ul;
-
-  for (i=UE_list->head_ul; i>=0; i=UE_list->next_ul[i]) {
-    if (i == UE_id) {
-      // link prev to next in Active list
-      if (i==UE_list->head_ul) {
-        UE_list->head_ul = UE_list->next_ul[i];
-      } else {
-        UE_list->next_ul[prev] = UE_list->next_ul[i];
-      }
-
-      // add UE id (i)to available
-      UE_list->next_ul[i] = UE_list->avail;
-      ret = 0;
-      break;
-    }
-
-    prev=i;
-  }
-
   mac_phy_remove_ue(mod_idP,rntiP);
 
   // check if this has an RA process active
@@ -376,15 +326,8 @@ int rrc_mac_remove_ue(module_id_t mod_idP,rnti_t rntiP)
       //break;
     }
   }
-  if (ret == 0) {
-    return (0);
-  }
-
-  LOG_E(MAC,"error in mac_remove_ue(), could not find previous to %d in UE_list, should never happen, Dumping UE list\n",UE_id);
-  dump_ue_list(UE_list,0);
-  mac_xface->macphy_exit("mac_remove_ue: Problem in UE_list");
-  return(-1);
 
+  return 0;
 }