/*
* 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 <[email protected]>
*/

#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;
}

/* a wrapper to make debug_smp_processor_id() happy
* we can use sched_clock() because we don't care much about precision
* we only care that the average is bounded
*/
#ifdef CONFIG_DEBUG_PREEMPT
static inline u64 busy_loop_us_clock(void)
{
u64 rc;

preempt_disable_notrace();
rc = sched_clock();
preempt_enable_no_resched_notrace();

return rc >> 10;
}
#else /* CONFIG_DEBUG_PREEMPT */
static inline u64 busy_loop_us_clock(void)
{
return sched_clock() >> 10;
}
#endif /* CONFIG_DEBUG_PREEMPT */

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 */