Re: [B.A.T.M.A.N.] [PATCH 5/7] batman-adv: Make bat_priv->curr_gw an rcu protected pointer

On Friday 04 February 2011 16:21:34 Linus Lüssing wrote:

• if (curr_gw) {

• rcu_read_unlock();
  

  return;
• }

• rcu_read_lock(); if (hlist_empty(&bat_priv->gw_list)) {

• rcu_read_unlock();
  
  

• if (bat_priv->curr_gw) {
  

• if (curr_gw) {
  

• 	rcu_read_unlock();
  bat_dbg(DBG_BATMAN, bat_priv,
  	"Removing selected gateway - "
  	"no gateway in range\n");
  gw_deselect(bat_priv);
  

  }

• else
  

• 	rcu_read_unlock();
  

This is a bit odd here - we return if curr_gw is not NULL and later we print a message if curr_gw is not NULL ? The issue existed before your patch came along.

void gw_check_election(struct bat_priv *bat_priv, struct orig_node *orig_node) {

• struct gw_node *curr_gateway_tmp = bat_priv->curr_gw;

• struct gw_node *curr_gateway_tmp; uint8_t gw_tq_avg, orig_tq_avg;

• rcu_read_lock();

• curr_gateway_tmp = rcu_dereference(bat_priv->curr_gw); if (!curr_gateway_tmp)

• return;
  

• goto rcu_unlock;
  
  

  if (!curr_gateway_tmp->orig_node) goto deselect;

It seems if we jump to "deselect" here the rcu_lock() will never be unlocked.

@@ -316,7 +342,7 @@ void gw_node_purge(struct bat_priv *bat_priv)

• if (bat_priv->curr_gw == gw_node)
  

• if (rcu_dereference(bat_priv->curr_gw) == gw_node)
  gw_deselect(bat_priv);
  

At this point we neither hold a rcu_lock() nor the newly created spinlock ...

spinlock_t gw_list_lock; /* protects gw_list */

• spinlock_t curr_gw_lock; /* protects curr_gw updates */

Would speak anything against re-using the gw_list_lock ?

Regards, Marek