![Neil Horman](/assets/img/avatar_default.png)
Bart Van Assche recently reported a warning to me:
<IRQ> [<ffffffff8103d79f>] warn_slowpath_common+0x7f/0xc0
[<ffffffff8103d7fa>] warn_slowpath_null+0x1a/0x20
[<ffffffff814761dd>] mutex_trylock+0x16d/0x180
[<ffffffff813968c9>] netpoll_poll_dev+0x49/0xc30
[<ffffffff8136a2d2>] ? __alloc_skb+0x82/0x2a0
[<ffffffff81397715>] netpoll_send_skb_on_dev+0x265/0x410
[<ffffffff81397c5a>] netpoll_send_udp+0x28a/0x3a0
[<ffffffffa0541843>] ? write_msg+0x53/0x110 [netconsole]
[<ffffffffa05418bf>] write_msg+0xcf/0x110 [netconsole]
[<ffffffff8103eba1>] call_console_drivers.constprop.17+0xa1/0x1c0
[<ffffffff8103fb76>] console_unlock+0x2d6/0x450
[<ffffffff8104011e>] vprintk_emit+0x1ee/0x510
[<ffffffff8146f9f6>] printk+0x4d/0x4f
[<ffffffffa0004f1d>] scsi_print_command+0x7d/0xe0 [scsi_mod]
This resulted from my commit ca99ca14c
which introduced a mutex_trylock
operation in a path that could execute in interrupt context. When mutex
debugging is enabled, the above warns the user when we are in fact
exectuting in interrupt context
interrupt context.
After some discussion, It seems that a semaphore is the proper mechanism to use
here. While mutexes are defined to be unusable in interrupt context, no such
condition exists for semaphores (save for the fact that the non blocking api
calls, like up and down_trylock must be used when in irq context).
Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Reported-by: Bart Van Assche <bvanassche@acm.org>
CC: Bart Van Assche <bvanassche@acm.org>
CC: David Miller <davem@davemloft.net>
CC: netdev@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>
181 lines
4 KiB
C
181 lines
4 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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union inet_addr {
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__u32 all[4];
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__be32 ip;
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__be32 ip6[4];
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struct in_addr in;
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struct in6_addr in6;
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};
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struct netpoll {
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struct net_device *dev;
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char dev_name[IFNAMSIZ];
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const char *name;
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void (*rx_hook)(struct netpoll *, int, char *, int);
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union inet_addr local_ip, remote_ip;
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bool ipv6;
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u16 local_port, remote_port;
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u8 remote_mac[ETH_ALEN];
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struct list_head rx; /* rx_np list element */
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struct work_struct cleanup_work;
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};
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struct netpoll_info {
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atomic_t refcnt;
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unsigned long rx_flags;
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spinlock_t rx_lock;
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struct semaphore dev_lock;
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struct list_head rx_np; /* netpolls that registered an rx_hook */
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struct sk_buff_head neigh_tx; /* list of neigh requests to reply to */
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struct sk_buff_head txq;
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struct delayed_work tx_work;
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struct netpoll *netpoll;
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struct rcu_head rcu;
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};
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#ifdef CONFIG_NETPOLL
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extern int netpoll_rx_disable(struct net_device *dev);
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extern void netpoll_rx_enable(struct net_device *dev);
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#else
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static inline int netpoll_rx_disable(struct net_device *dev) { return 0; }
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static inline void netpoll_rx_enable(struct net_device *dev) { return; }
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#endif
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void netpoll_send_udp(struct netpoll *np, const char *msg, int len);
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void netpoll_print_options(struct netpoll *np);
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int netpoll_parse_options(struct netpoll *np, char *opt);
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int __netpoll_setup(struct netpoll *np, struct net_device *ndev, gfp_t gfp);
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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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void __netpoll_free_async(struct netpoll *np);
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void netpoll_cleanup(struct netpoll *np);
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int __netpoll_rx(struct sk_buff *skb, struct netpoll_info *npinfo);
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void netpoll_send_skb_on_dev(struct netpoll *np, struct sk_buff *skb,
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struct net_device *dev);
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static inline void netpoll_send_skb(struct netpoll *np, struct sk_buff *skb)
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{
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unsigned long flags;
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local_irq_save(flags);
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netpoll_send_skb_on_dev(np, skb, np->dev);
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local_irq_restore(flags);
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}
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#ifdef CONFIG_NETPOLL
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static inline bool netpoll_rx_on(struct sk_buff *skb)
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{
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struct netpoll_info *npinfo = rcu_dereference_bh(skb->dev->npinfo);
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return npinfo && (!list_empty(&npinfo->rx_np) || npinfo->rx_flags);
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}
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static inline bool netpoll_rx(struct sk_buff *skb)
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{
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struct netpoll_info *npinfo;
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unsigned long flags;
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bool ret = false;
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local_irq_save(flags);
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if (!netpoll_rx_on(skb))
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goto out;
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npinfo = rcu_dereference_bh(skb->dev->npinfo);
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spin_lock(&npinfo->rx_lock);
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/* check rx_flags again with the lock held */
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if (npinfo->rx_flags && __netpoll_rx(skb, npinfo))
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ret = true;
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spin_unlock(&npinfo->rx_lock);
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out:
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local_irq_restore(flags);
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return ret;
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}
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static inline int netpoll_receive_skb(struct sk_buff *skb)
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{
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if (!list_empty(&skb->dev->napi_list))
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return netpoll_rx(skb);
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return 0;
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}
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static inline void *netpoll_poll_lock(struct napi_struct *napi)
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{
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struct net_device *dev = napi->dev;
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if (dev && dev->npinfo) {
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spin_lock(&napi->poll_lock);
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napi->poll_owner = smp_processor_id();
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return napi;
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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 napi_struct *napi = have;
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if (napi) {
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napi->poll_owner = -1;
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spin_unlock(&napi->poll_lock);
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}
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}
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static inline bool netpoll_tx_running(struct net_device *dev)
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{
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return irqs_disabled();
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}
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#else
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static inline bool netpoll_rx(struct sk_buff *skb)
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{
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return false;
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}
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static inline bool netpoll_rx_on(struct sk_buff *skb)
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{
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return false;
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}
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static inline int netpoll_receive_skb(struct sk_buff *skb)
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{
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return 0;
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}
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static inline void *netpoll_poll_lock(struct napi_struct *napi)
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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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}
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static inline void netpoll_netdev_init(struct net_device *dev)
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{
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}
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static inline bool netpoll_tx_running(struct net_device *dev)
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{
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return false;
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}
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#endif
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#endif
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