Commit fbeec2e1 authored by Jeff Moyer's avatar Jeff Moyer Committed by David S. Miller

[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: default avatarJeff Moyer <>
Signed-off-by: default avatarDavid S. Miller <>
parent 115c1d6e
......@@ -27,7 +27,8 @@ struct netpoll_info {
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 @@ void netpoll_queue(struct sk_buff *skb);
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)
......@@ -349,11 +349,15 @@ static void arp_reply(struct sk_buff *skb)
unsigned char *arp_ptr;
int size, type = ARPOP_REPLY, ptype = ETH_P_ARP;
u32 sip, tip;
unsigned long flags;
struct sk_buff *send_skb;
struct netpoll *np = NULL;
if (npinfo)
np = npinfo->np;
spin_lock_irqsave(&npinfo->rx_lock, flags);
if (npinfo->rx_np && npinfo->rx_np->dev == skb->dev)
np = npinfo->rx_np;
spin_unlock_irqrestore(&npinfo->rx_lock, flags);
if (!np)
......@@ -436,9 +440,9 @@ int __netpoll_rx(struct sk_buff *skb)
int proto, len, ulen;
struct iphdr *iph;
struct udphdr *uh;
struct netpoll *np = skb->dev->npinfo->np;
struct netpoll *np = skb->dev->npinfo->rx_np;
if (!np->rx_hook)
if (!np)
goto out;
if (skb->dev->type != ARPHRD_ETHER)
goto out;
......@@ -619,6 +623,7 @@ int netpoll_setup(struct netpoll *np)
struct net_device *ndev = NULL;
struct in_device *in_dev;
struct netpoll_info *npinfo;
unsigned long flags;
if (np->dev_name)
ndev = dev_get_by_name(np->dev_name);
......@@ -634,9 +639,10 @@ int netpoll_setup(struct netpoll *np)
if (!npinfo)
goto release;
npinfo->np = NULL;
npinfo->rx_np = NULL;
npinfo->poll_lock = SPIN_LOCK_UNLOCKED;
npinfo->poll_owner = -1;
npinfo->rx_lock = SPIN_LOCK_UNLOCKED;
} else
npinfo = ndev->npinfo;
......@@ -706,9 +712,13 @@ int netpoll_setup(struct netpoll *np)
np->name, HIPQUAD(np->local_ip));
npinfo->rx_flags = NETPOLL_RX_ENABLED;
npinfo->np = np;
if (np->rx_hook) {
spin_lock_irqsave(&npinfo->rx_lock, flags);
npinfo->rx_flags |= NETPOLL_RX_ENABLED;
npinfo->rx_np = np;
spin_unlock_irqrestore(&npinfo->rx_lock, flags);
/* last thing to do is link it to the net device structure */
ndev->npinfo = npinfo;
return 0;
......@@ -723,11 +733,20 @@ int netpoll_setup(struct netpoll *np)
void netpoll_cleanup(struct netpoll *np)
struct netpoll_info *npinfo;
unsigned long flags;
if (np->dev) {
if (np->dev->npinfo)
np->dev->npinfo->np = NULL;
npinfo = np->dev->npinfo;
if (npinfo && npinfo->rx_np == np) {
spin_lock_irqsave(&npinfo->rx_lock, flags);
npinfo->rx_np = NULL;
npinfo->rx_flags &= ~NETPOLL_RX_ENABLED;
spin_unlock_irqrestore(&npinfo->rx_lock, flags);
np->dev = NULL;
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