068c6e98bc
The netpoll system currently has a rx to tx path via:
netpoll_rx
__netpoll_rx
arp_reply
netpoll_send_skb
dev->hard_start_tx
This rx->tx loop places network drivers at risk of inadvertently causing a
deadlock or BUG halt by recursively trying to acquire a spinlock that is
used in both their rx and tx paths (this problem was origionally reported
to me in the 3c59x driver, which shares a spinlock between the
boomerang_interrupt and boomerang_start_xmit routines).
This patch breaks this loop, by queueing arp frames, so that they can be
responded to after all receive operations have been completed. Tested by
myself and the reported with successful results.
Specifically it was tested with netdump. Heres the BZ with details:
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=194055
Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
94 lines
2.2 KiB
C
94 lines
2.2 KiB
C
/*
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* Common code for low-level network console, dump, and debugger code
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*
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* Derived from netconsole, kgdb-over-ethernet, and netdump patches
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*/
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#ifndef _LINUX_NETPOLL_H
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#define _LINUX_NETPOLL_H
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#include <linux/netdevice.h>
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#include <linux/interrupt.h>
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#include <linux/rcupdate.h>
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#include <linux/list.h>
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struct netpoll;
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struct netpoll {
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struct net_device *dev;
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char dev_name[16], *name;
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void (*rx_hook)(struct netpoll *, int, char *, int);
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void (*drop)(struct sk_buff *skb);
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u32 local_ip, remote_ip;
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u16 local_port, remote_port;
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unsigned char local_mac[6], remote_mac[6];
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};
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struct netpoll_info {
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spinlock_t poll_lock;
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int poll_owner;
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int tries;
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int rx_flags;
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spinlock_t rx_lock;
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struct netpoll *rx_np; /* netpoll that registered an rx_hook */
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struct sk_buff_head arp_tx; /* list of arp requests to reply to */
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};
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void netpoll_poll(struct netpoll *np);
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void netpoll_send_udp(struct netpoll *np, const char *msg, int len);
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int netpoll_parse_options(struct netpoll *np, char *opt);
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int netpoll_setup(struct netpoll *np);
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int netpoll_trap(void);
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void netpoll_set_trap(int trap);
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void netpoll_cleanup(struct netpoll *np);
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int __netpoll_rx(struct sk_buff *skb);
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void netpoll_queue(struct sk_buff *skb);
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#ifdef CONFIG_NETPOLL
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static inline int netpoll_rx(struct sk_buff *skb)
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{
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struct netpoll_info *npinfo = skb->dev->npinfo;
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unsigned long flags;
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int ret = 0;
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if (!npinfo || (!npinfo->rx_np && !npinfo->rx_flags))
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return 0;
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spin_lock_irqsave(&npinfo->rx_lock, flags);
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/* check rx_flags again with the lock held */
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if (npinfo->rx_flags && __netpoll_rx(skb))
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ret = 1;
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spin_unlock_irqrestore(&npinfo->rx_lock, flags);
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return ret;
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}
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static inline void *netpoll_poll_lock(struct net_device *dev)
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{
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rcu_read_lock(); /* deal with race on ->npinfo */
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if (dev->npinfo) {
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spin_lock(&dev->npinfo->poll_lock);
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dev->npinfo->poll_owner = smp_processor_id();
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return dev->npinfo;
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}
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return NULL;
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}
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static inline void netpoll_poll_unlock(void *have)
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{
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struct netpoll_info *npi = have;
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if (npi) {
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npi->poll_owner = -1;
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spin_unlock(&npi->poll_lock);
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}
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rcu_read_unlock();
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}
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#else
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#define netpoll_rx(a) 0
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#define netpoll_poll_lock(a) NULL
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#define netpoll_poll_unlock(a)
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#endif
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#endif
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