From 9a95eedc81deb86af1ac56f2c2bfe8306b27b82a Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 5 Sep 2024 08:49:09 +0000 Subject: [PATCH] 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: Eric Dumazet Reviewed-by: Breno Leitao Link: https://patch.msgid.link/20240905084909.2082486-1-edumazet@google.com Signed-off-by: Jakub Kicinski --- net/core/netpoll.c | 15 ++++----------- 1 file changed, 4 insertions(+), 11 deletions(-) diff --git a/net/core/netpoll.c b/net/core/netpoll.c index e0720ee6fa62..ca52cbe0f63c 100644 --- a/net/core/netpoll.c +++ b/net/core/netpoll.c @@ -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;