Commit 84a7d679 authored by Eric Dumazet's avatar Eric Dumazet Committed by Paolo Abeni
Browse files

net/sched: acp_api: no longer acquire RTNL in tc_action_net_exit() 



tc_action_net_exit() got an rtnl exclusion in commit
a159d3c4 ("net_sched: acquire RTNL in tc_action_net_exit()")

Since then, commit 16af6067 ("net: sched: implement reference
counted action release") made this RTNL exclusion obsolete for
most cases.

Only tcf_action_offload_del() might still require it.

Move the rtnl locking into tcf_idrinfo_destroy() when
an offload action is found.

Most netns do not have actions, yet deleting them is adding a lot
of pressure on RTNL, which is for many the most contended mutex
in the kernel.

We are moving to a per-netns 'rtnl', so tc_action_net_exit()
will not be able to grab 'rtnl' a single time for a batch of netns.

Before the patch:

perf probe -a rtnl_lock

perf record -e probe:rtnl_lock -a /bin/bash -c 'unshare -n "/bin/true"; sleep 1'
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.305 MB perf.data (25 samples) ]

After the patch:

perf record -e probe:rtnl_lock -a /bin/bash -c 'unshare -n "/bin/true"; sleep 1'
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.304 MB perf.data (9 samples) ]

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Cc: Vlad Buslov <vladbu@nvidia.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Cc: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Link: https://patch.msgid.link/20250702071230.1892674-1-edumazet@google.com


Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent d23647fd

include/net/act_api.h

+0 −2
Original line number Diff line number Diff line
@@ -170,14 +170,12 @@ static inline void tc_action_net_exit(struct list_head *net_list, 
{

	struct net *net;



	rtnl_lock();

	list_for_each_entry(net, net_list, exit_list) {

		struct tc_action_net *tn = net_generic(net, id);



		tcf_idrinfo_destroy(tn->ops, tn->idrinfo);

		kfree(tn->idrinfo);

	}

	rtnl_unlock();

}



int tcf_generic_walker(struct tc_action_net *tn, struct sk_buff *skb,

net/sched/act_api.c

+8 −1
Original line number Diff line number Diff line
@@ -933,18 +933,25 @@ void tcf_idrinfo_destroy(const struct tc_action_ops *ops, 
			 struct tcf_idrinfo *idrinfo)

{

	struct idr *idr = &idrinfo->action_idr;

	bool mutex_taken = false;

	struct tc_action *p;

	int ret;

	unsigned long id = 1;

	unsigned long tmp;

	int ret;



	idr_for_each_entry_ul(idr, p, tmp, id) {

		if (tc_act_in_hw(p) && !mutex_taken) {

			rtnl_lock();

			mutex_taken = true;

		}

		ret = __tcf_idr_release(p, false, true);

		if (ret == ACT_P_DELETED)

			module_put(ops->owner);

		else if (ret < 0)

			return;

	}

	if (mutex_taken)

		rtnl_unlock();

	idr_destroy(&idrinfo->action_idr);

}

EXPORT_SYMBOL(tcf_idrinfo_destroy);