[NETPOLL]: allow multiple netpoll_clients to register against one interface
This patch provides support for registering multiple netpoll clients to the
same network device. Only one of these clients may register an rx_hook,
however. In practice, this restriction has not been problematic. It is
worth mentioning, though, that the current design can be easily extended to
allow for the registration of multiple rx_hooks.
The basic idea of the patch is that the rx_np pointer in the netpoll_info
structure points to the struct netpoll that has rx_hook filled in. Aside
from this one case, there is no need for a pointer from the struct
net_device to an individual struct netpoll.
A lock is introduced to protect the setting and clearing of the np_rx
pointer. The pointer will only be cleared upon netpoll client module
removal, and the lock should be uncontested.
Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h
index 388cd91..bcd0ac3 100644
--- a/include/linux/netpoll.h
+++ b/include/linux/netpoll.h
@@ -27,7 +27,8 @@
spinlock_t poll_lock;
int poll_owner;
int rx_flags;
- struct netpoll *np;
+ spinlock_t rx_lock;
+ struct netpoll *rx_np; /* netpoll that registered an rx_hook */
};
void netpoll_poll(struct netpoll *np);
@@ -44,11 +45,19 @@
static inline int netpoll_rx(struct sk_buff *skb)
{
struct netpoll_info *npinfo = skb->dev->npinfo;
+ unsigned long flags;
+ int ret = 0;
- if (!npinfo || !npinfo->rx_flags)
+ if (!npinfo || (!npinfo->rx_np && !npinfo->rx_flags))
return 0;
- return npinfo->np && __netpoll_rx(skb);
+ spin_lock_irqsave(&npinfo->rx_lock, flags);
+ /* check rx_flags again with the lock held */
+ if (npinfo->rx_flags && __netpoll_rx(skb))
+ ret = 1;
+ spin_unlock_irqrestore(&npinfo->rx_lock, flags);
+
+ return ret;
}
static inline void netpoll_poll_lock(struct net_device *dev)