Commit 0734d7c3 authored by Eric Dumazet's avatar Eric Dumazet Committed by Jakub Kicinski
Browse files

net: expedite synchronize_net() for cleanup_net() 



cleanup_net() is the single thread responsible
for netns dismantles, and a serious bottleneck.

Before we can get per-netns RTNL, make sure
all synchronize_net() called from this thread
are using rcu_synchronize_expedited().

v3: deal with CONFIG_NET_NS=n

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reviewed-by: default avatarJesse Brandeburg <jbrandeburg@cloudflare.com>
Link: https://patch.msgid.link/20250114205531.967841-2-edumazet@google.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 0b6f6593

include/net/net_namespace.h

+2 −0
Original line number Diff line number Diff line
@@ -210,6 +210,8 @@ void net_ns_barrier(void); 


struct ns_common *get_net_ns(struct ns_common *ns);

struct net *get_net_ns_by_fd(int fd);

extern struct task_struct *cleanup_net_task;



#else /* CONFIG_NET_NS */

#include <linux/sched.h>

#include <linux/nsproxy.h>

net/core/dev.c

+10 −1
Original line number Diff line number Diff line
@@ -10099,6 +10099,15 @@ static void dev_index_release(struct net *net, int ifindex) 
	WARN_ON(xa_erase(&net->dev_by_index, ifindex));

}



static bool from_cleanup_net(void)

{

#ifdef CONFIG_NET_NS

	return current == cleanup_net_task;

#else

	return false;

#endif

}



/* Delayed registration/unregisteration */

LIST_HEAD(net_todo_list);

DECLARE_WAIT_QUEUE_HEAD(netdev_unregistering_wq);
@@ -11474,7 +11483,7 @@ EXPORT_SYMBOL_GPL(alloc_netdev_dummy); 
void synchronize_net(void)

{

	might_sleep();

	if (rtnl_is_locked())

	if (from_cleanup_net() || rtnl_is_locked())

		synchronize_rcu_expedited();

	else

		synchronize_rcu();

net/core/net_namespace.c

+5 −0
Original line number Diff line number Diff line
@@ -588,6 +588,8 @@ static void unhash_nsid(struct net *net, struct net *last) 


static LLIST_HEAD(cleanup_list);



struct task_struct *cleanup_net_task;



static void cleanup_net(struct work_struct *work)

{

	const struct pernet_operations *ops;
@@ -596,6 +598,8 @@ static void cleanup_net(struct work_struct *work) 
	LIST_HEAD(net_exit_list);

	LIST_HEAD(dev_kill_list);



	cleanup_net_task = current;



	/* Atomically snapshot the list of namespaces to cleanup */

	net_kill_list = llist_del_all(&cleanup_list);
@@ -670,6 +674,7 @@ static void cleanup_net(struct work_struct *work) 
		put_user_ns(net->user_ns);

		net_free(net);

	}

	cleanup_net_task = NULL;

}



/**