From 9d07e0432c5ec0fb3454cecac68f8deb6b057407 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 14 Mar 2022 09:58:15 +0800 Subject: [PATCH] netns: add schedule point in ops_exit_list() stable inclusion from linux-4.19.226 commit 4048cedfd16a995b2ef4294b9539da17e2fea750 -------------------------------- 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 Cc: Eric W. Biederman Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman Signed-off-by: Yongqiang Liu Signed-off-by: Laibin Qiu Signed-off-by: Yongqiang Liu --- 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); -- GitLab