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netns: add schedule point in ops_exit_list()

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commit 2836615aa2 upstream.

When under stress, cleanup_net() can have to dismantle
netns in big numbers. ops_exit_list() currently calls
many helpers [1] that have no schedule point, and we can
end up with soft lockups, particularly on hosts
with many cpus.

Even for moderate amount of netns processed by cleanup_net()
this patch avoids latency spikes.

[1] Some of these helpers like fib_sync_up() and fib_sync_down_dev()
are very slow because net/ipv4/fib_semantics.c uses host-wide hash tables,
and ifindex is used as the only input of two hash functions.
    ifindexes tend to be the same for all netns (lo.ifindex==1 per instance)
    This will be fixed in a separate patch.

Fixes: 72ad937abd ("net: Add support for batching network namespace cleanups")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Eric Dumazet 2022-01-18 03:43:40 -08:00 committed by Greg Kroah-Hartman
parent edc09548ff
commit 2b1415c60b
1 changed files with 3 additions and 1 deletions
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4
net/core/net_namespace.c
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@ -183,8 +183,10 @@ static void ops_exit_list(const struct pernet_operations *ops,
{ {
struct net *net; struct net *net;
if (ops->exit) { if (ops->exit) {
list_for_each_entry(net, net_exit_list, exit_list) list_for_each_entry(net, net_exit_list, exit_list) {
ops->exit(net); ops->exit(net);
cond_resched();
}
} }
if (ops->exit_batch) if (ops->exit_batch)
ops->exit_batch(net_exit_list); ops->exit_batch(net_exit_list);