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netpoll: remove netpoll_srcu

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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 <edumazet@google.com>
Reviewed-by: Breno Leitao <leitao@debian.org>
Link: https://patch.msgid.link/20240905084909.2082486-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2024-09-05 08:49:09 +00:00 committed by Jakub Kicinski
parent c6a1739778
commit 9a95eedc81
1 changed files with 4 additions and 11 deletions
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15
net/core/netpoll.c
View File

@ -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;