/*
   * net busy poll support
   * Copyright(c) 2013 Intel Corporation.
   *
   * This program is free software; you can redistribute it and/or modify it
   * under the terms and conditions of the GNU General Public License,
   * version 2, as published by the Free Software Foundation.
   *
   * This program is distributed in the hope it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
   * more details.
   *
   * You should have received a copy of the GNU General Public License along with
   * this program; if not, write to the Free Software Foundation, Inc.,
   * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Author: Eliezer Tamir
   *
   * Contact Information:
   * e1000-devel Mailing List <e1000-devel@lists.sourceforge.net>
   */
  
  #ifndef _LINUX_NET_BUSY_POLL_H
  #define _LINUX_NET_BUSY_POLL_H
  
  #include <linux/netdevice.h>
  #include <net/ip.h>
  
  #ifdef CONFIG_NET_RX_BUSY_POLL
  
  struct napi_struct;
  extern unsigned int sysctl_net_busy_read __read_mostly;
  extern unsigned int sysctl_net_busy_poll __read_mostly;
  
  /* return values from ndo_ll_poll */
  #define LL_FLUSH_FAILED		-1
  #define LL_FLUSH_BUSY		-2
  
  static inline bool net_busy_loop_on(void)
  {
  	return sysctl_net_busy_poll;
  }
  
  static inline u64 busy_loop_us_clock(void)
  {
  	return local_clock() >> 10;
  }
  
  static inline unsigned long sk_busy_loop_end_time(struct sock *sk)
  {
  	return busy_loop_us_clock() + ACCESS_ONCE(sk->sk_ll_usec);
  }
  
  /* in poll/select we use the global sysctl_net_ll_poll value */
  static inline unsigned long busy_loop_end_time(void)
  {
  	return busy_loop_us_clock() + ACCESS_ONCE(sysctl_net_busy_poll);
  }
  
  static inline bool sk_can_busy_loop(struct sock *sk)
  {
  	return sk->sk_ll_usec && sk->sk_napi_id &&
  	       !need_resched() && !signal_pending(current);
  }
  
  
  static inline bool busy_loop_timeout(unsigned long end_time)
  {
  	unsigned long now = busy_loop_us_clock();
  
  	return time_after(now, end_time);
  }
  
  /* when used in sock_poll() nonblock is known at compile time to be true
   * so the loop and end_time will be optimized out
   */
  static inline bool sk_busy_loop(struct sock *sk, int nonblock)
  {
  	unsigned long end_time = !nonblock ? sk_busy_loop_end_time(sk) : 0;
  	const struct net_device_ops *ops;
  	struct napi_struct *napi;
  	int rc = false;
  
  	/*
  	 * rcu read lock for napi hash
  	 * bh so we don't race with net_rx_action
  	 */
  	rcu_read_lock_bh();
  
  	napi = napi_by_id(sk->sk_napi_id);
  	if (!napi)
  		goto out;
  
  	ops = napi->dev->netdev_ops;
  	if (!ops->ndo_busy_poll)
  		goto out;
  
  	do {
  		rc = ops->ndo_busy_poll(napi);
  
  		if (rc == LL_FLUSH_FAILED)
  			break; /* permanent failure */
  
  		if (rc > 0)
  			/* local bh are disabled so it is ok to use _BH */
  			NET_ADD_STATS_BH(sock_net(sk),
  					 LINUX_MIB_BUSYPOLLRXPACKETS, rc);
  		cpu_relax();
  
  	} while (!nonblock && skb_queue_empty(&sk->sk_receive_queue) &&
  		 !need_resched() && !busy_loop_timeout(end_time));
  
  	rc = !skb_queue_empty(&sk->sk_receive_queue);
  out:
  	rcu_read_unlock_bh();
  	return rc;
  }
  
  /* used in the NIC receive handler to mark the skb */
  static inline void skb_mark_napi_id(struct sk_buff *skb,
  				    struct napi_struct *napi)
  {
  	skb->napi_id = napi->napi_id;
  }
  
  /* used in the protocol hanlder to propagate the napi_id to the socket */
  static inline void sk_mark_napi_id(struct sock *sk, struct sk_buff *skb)
  {
  	sk->sk_napi_id = skb->napi_id;
  }
  
  #else /* CONFIG_NET_RX_BUSY_POLL */
  static inline unsigned long net_busy_loop_on(void)
  {
  	return 0;
  }
  
  static inline unsigned long busy_loop_end_time(void)
  {
  	return 0;
  }
  
  static inline bool sk_can_busy_loop(struct sock *sk)
  {
  	return false;
  }
  
  static inline void skb_mark_napi_id(struct sk_buff *skb,
  				    struct napi_struct *napi)
  {
  }
  
  static inline void sk_mark_napi_id(struct sock *sk, struct sk_buff *skb)
  {
  }
  
  static inline bool busy_loop_timeout(unsigned long end_time)
  {
  	return true;
  }
  
  static inline bool sk_busy_loop(struct sock *sk, int nonblock)
  {
  	return false;
  }
  
  #endif /* CONFIG_NET_RX_BUSY_POLL */
  #endif /* _LINUX_NET_BUSY_POLL_H */