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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: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2022-02-25 08:18:55 -08:00 committed by David S. Miller
parent 6a4696c428
commit b3483bc7a1
1 changed files with 2 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
net/core/sysctl_net_core.c
View File

@ -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));