On Mon, Oct 20, 2025 at 03:25:40PM +0300, Dan Carpenter wrote:

netrom/nr_route.c
   214          nr_node_lock(nr_node);

I guess nr_node is different for each thread?

   215  
   216          if (quality != 0)
   217                  strscpy(nr_node->mnemonic, mnemonic);
   218  
   219          for (found = 0, i = 0; i < nr_node->count; i++) {
   220                  if (nr_node->routes[i].neighbour == nr_neigh) {
   221                          nr_node->routes[i].quality   = quality;
   222                          nr_node->routes[i].obs_count = obs_count;
   223                          found = 1;
   224                          break;
   225                  }
   226          }
   227  
   228          if (!found) {
   229                  /* We have space at the bottom, slot it in */
   230                  if (nr_node->count < 3) {
   231                          nr_node->routes[2] = nr_node->routes[1];
   232                          nr_node->routes[1] = nr_node->routes[0];
   233  
   234                          nr_node->routes[0].quality   = quality;
   235                          nr_node->routes[0].obs_count = obs_count;
   236                          nr_node->routes[0].neighbour = nr_neigh;
   237  
   238                          nr_node->which++;
   239                          nr_node->count++;
   240                          nr_neigh_hold(nr_neigh);
   241                          nr_neigh->count++;
   242                  } else {
   243                          /* It must be better than the worst */
   244                          if (quality > nr_node->routes[2].quality) {
   245                                  nr_node->routes[2].neighbour->count--;
   246                                  nr_neigh_put(nr_node->routes[2].neighbour);
   247  
   248                                  if (nr_node->routes[2].neighbour->count == 0 && !nr_node->routes[2].neighbour->locked)
   249                                          nr_remove_neigh(nr_node->routes[2].neighbour);

Does neighbour->count means how many nr_node pointers have it in ->routes[]?
I wish this code had comments.
KTDOO: add comments explaining all the counters in netrom/nr_route.c

   250  
   251                                  nr_node->routes[2].quality   = quality;
   252                                  nr_node->routes[2].obs_count = obs_count;
   253                                  nr_node->routes[2].neighbour = nr_neigh;
   254  
   255                                  nr_neigh_hold(nr_neigh);
   256                                  nr_neigh->count++;

Could we just add some locking to this if statement only?  I had thought
that nr_node_lock() serialized it but now I think maybe not?  Or maybe we
could increment the counters before assigning it?

			nr_neigh->count++;
			nr_neigh_hold(nr_neigh);
			nr_node->routes[2].neighbour = nr_neigh;

I'm not an expert in concerency.  Does calling nr_neigh_hold() mean th
that the nr_neigh->count++ will happen before the assignment?

   257                          }
   258                  }
   259          }

regards,
dan carpenter