[PATCH ipvs-next v3 2/2] ipvs: use cond_resched_rcu() helper when walking connections

[Simon Horman <horms@xxxxxxxxxxxx>]

This avoids the situation where walking of a large number of connections
may prevent scheduling for a long time while also avoiding excessive
calls to rcu_read_unlock() and rcu_read_lock().

Note that in the case of !CONFIG_PREEMPT_RCU this will
add a call to cond_resched().

[ja@xxxxxx: add cond_resched_rcu to more places]
Signed-off-by: Julian Anastasov <ja@xxxxxx>
Signed-off-by: Simon Horman <horms@xxxxxxxxxxxx>
---
 net/netfilter/ipvs/ip_vs_conn.c | 23 ++++++++---------------
 1 file changed, 8 insertions(+), 15 deletions(-)

diff --git a/net/netfilter/ipvs/ip_vs_conn.c b/net/netfilter/ipvs/ip_vs_conn.c
index a083bda..c8c52a9 100644
--- a/net/netfilter/ipvs/ip_vs_conn.c
+++ b/net/netfilter/ipvs/ip_vs_conn.c
@@ -975,8 +975,7 @@ static void *ip_vs_conn_array(struct seq_file *seq, loff_t 
pos)
                                return cp;
                        }
                }
-               rcu_read_unlock();
-               rcu_read_lock();
+               cond_resched_rcu();
        }
 
        return NULL;
@@ -1015,8 +1014,7 @@ static void *ip_vs_conn_seq_next(struct seq_file *seq, 
void *v, loff_t *pos)
                        iter->l = &ip_vs_conn_tab[idx];
                        return cp;
                }
-               rcu_read_unlock();
-               rcu_read_lock();
+               cond_resched_rcu();
        }
        iter->l = NULL;
        return NULL;
@@ -1206,17 +1204,13 @@ void ip_vs_random_dropentry(struct net *net)
        int idx;
        struct ip_vs_conn *cp, *cp_c;
 
+       rcu_read_lock();
        /*
         * Randomly scan 1/32 of the whole table every second
         */
        for (idx = 0; idx < (ip_vs_conn_tab_size>>5); idx++) {
                unsigned int hash = net_random() & ip_vs_conn_tab_mask;
 
-               /*
-                *  Lock is actually needed in this loop.
-                */
-               rcu_read_lock();
-
                hlist_for_each_entry_rcu(cp, &ip_vs_conn_tab[hash], c_list) {
                        if (cp->flags & IP_VS_CONN_F_TEMPLATE)
                                /* connection template */
@@ -1252,8 +1246,9 @@ void ip_vs_random_dropentry(struct net *net)
                                __ip_vs_conn_put(cp);
                        }
                }
-               rcu_read_unlock();
+               cond_resched_rcu();
        }
+       rcu_read_unlock();
 }
 
 
@@ -1267,11 +1262,8 @@ static void ip_vs_conn_flush(struct net *net)
        struct netns_ipvs *ipvs = net_ipvs(net);
 
 flush_again:
+       rcu_read_lock();
        for (idx = 0; idx < ip_vs_conn_tab_size; idx++) {
-               /*
-                *  Lock is actually needed in this loop.
-                */
-               rcu_read_lock();
 
                hlist_for_each_entry_rcu(cp, &ip_vs_conn_tab[idx], c_list) {
                        if (!ip_vs_conn_net_eq(cp, net))
@@ -1286,8 +1278,9 @@ flush_again:
                                __ip_vs_conn_put(cp);
                        }
                }
-               rcu_read_unlock();
+               cond_resched_rcu();
        }
+       rcu_read_unlock();
 
        /* the counter may be not NULL, because maybe some conn entries
           are run by slow timer handler or unhashed but still referred */
-- 
1.8.2.1

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