This is a note to let you know that I've just added the patch titled
netns: add schedule point in ops_exit_list()
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
netns-add-schedule-point-in-ops_exit_list.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 2836615aa22de55b8fca5e32fe1b27a67cda625e Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@xxxxxxxxxx>
Date: Tue, 18 Jan 2022 03:43:40 -0800
Subject: netns: add schedule point in ops_exit_list()
From: Eric Dumazet <edumazet@xxxxxxxxxx>
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@xxxxxxxxxx>
Cc: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/core/net_namespace.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -130,8 +130,10 @@ static void ops_exit_list(const struct p
{
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);
Patches currently in stable-queue which might be from edumazet@xxxxxxxxxx are
queue-4.4/af_unix-annote-lockless-accesses-to-unix_tot_inflight-gc_in_progress.patch
queue-4.4/netns-add-schedule-point-in-ops_exit_list.patch
queue-4.4/ppp-ensure-minimum-packet-size-in-ppp_write.patch
