Commit 9a95eedc authored by Eric Dumazet's avatar Eric Dumazet Committed by Jakub Kicinski
Browse files

netpoll: remove netpoll_srcu 



netpoll_srcu is currently used from netpoll_poll_disable() and
__netpoll_cleanup()

Both functions run under RTNL, using netpoll_srcu adds confusion
and no additional protection.

Moreover the synchronize_srcu() call in __netpoll_cleanup() is
performed before clearing np->dev->npinfo, which violates RCU rules.

After this patch, netpoll_poll_disable() and netpoll_poll_enable()
simply use rtnl_dereference().

This saves a big chunk of memory (more than 192KB on platforms
with 512 cpus)

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reviewed-by: default avatarBreno Leitao <leitao@debian.org>
Link: https://patch.msgid.link/20240905084909.2082486-1-edumazet@google.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent c6a17397

net/core/netpoll.c

+4 −11
Original line number Diff line number Diff line
@@ -48,8 +48,6 @@ 


static struct sk_buff_head skb_pool;



DEFINE_STATIC_SRCU(netpoll_srcu);



#define USEC_PER_POLL	50



#define MAX_SKB_SIZE							\
@@ -220,23 +218,20 @@ EXPORT_SYMBOL(netpoll_poll_dev); 
void netpoll_poll_disable(struct net_device *dev)

{

	struct netpoll_info *ni;

	int idx;



	might_sleep();

	idx = srcu_read_lock(&netpoll_srcu);

	ni = srcu_dereference(dev->npinfo, &netpoll_srcu);

	ni = rtnl_dereference(dev->npinfo);

	if (ni)

		down(&ni->dev_lock);

	srcu_read_unlock(&netpoll_srcu, idx);

}



void netpoll_poll_enable(struct net_device *dev)

{

	struct netpoll_info *ni;

	rcu_read_lock();

	ni = rcu_dereference(dev->npinfo);



	ni = rtnl_dereference(dev->npinfo);

	if (ni)

		up(&ni->dev_lock);

	rcu_read_unlock();

}



static void refill_skbs(void)
@@ -829,8 +824,6 @@ void __netpoll_cleanup(struct netpoll *np) 
	if (!npinfo)

		return;



	synchronize_srcu(&netpoll_srcu);



	if (refcount_dec_and_test(&npinfo->refcnt)) {

		const struct net_device_ops *ops;