Commit b3483bc7 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

net/sysctl: avoid two synchronize_rcu() calls 



Both rps_sock_flow_sysctl() and flow_limit_cpu_sysctl()
are using synchronize_rcu() right before freeing memory
either by vfree() or kfree()

They can switch to kvfree_rcu(ptr) and kfree_rcu(ptr) to benefit
from asynchronous mode, instead of blocking the current thread.

Note that kvfree_rcu(ptr) and kfree_rcu(ptr) eventually can
have to use synchronize_rcu() in some memory pressure cases.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 6a4696c4

net/core/sysctl_net_core.c

+2 −4
Original line number Diff line number Diff line
@@ -103,8 +103,7 @@ static int rps_sock_flow_sysctl(struct ctl_table *table, int write, 
			if (orig_sock_table) {

				static_branch_dec(&rps_needed);

				static_branch_dec(&rfs_needed);

				synchronize_rcu();

				vfree(orig_sock_table);

				kvfree_rcu(orig_sock_table);

			}

		}

	}
@@ -142,8 +141,7 @@ static int flow_limit_cpu_sysctl(struct ctl_table *table, int write, 
				     lockdep_is_held(&flow_limit_update_mutex));

			if (cur && !cpumask_test_cpu(i, mask)) {

				RCU_INIT_POINTER(sd->flow_limit, NULL);

				synchronize_rcu();

				kfree(cur);

				kfree_rcu(cur);

			} else if (!cur && cpumask_test_cpu(i, mask)) {

				cur = kzalloc_node(len, GFP_KERNEL,

						   cpu_to_node(i));