From: Eric Dumazet edumazet@google.com
stable inclusion from linux-4.19.226 commit 4048cedfd16a995b2ef4294b9539da17e2fea750
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commit 2836615aa22de55b8fca5e32fe1b27a67cda625e 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: 72ad937abd0a ("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 Signed-off-by: Yongqiang Liu liuyongqiang13@huawei.com Signed-off-by: Laibin Qiu qiulaibin@huawei.com --- net/core/net_namespace.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c index c60123dff803..f4aacbb76fa5 100644 --- a/net/core/net_namespace.c +++ b/net/core/net_namespace.c @@ -149,8 +149,10 @@ static void ops_exit_list(const struct pernet_operations *ops, { struct net *net; 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); + cond_resched(); + } } if (ops->exit_batch) ops->exit_batch(net_exit_list);