text: /* SPDX-License-Identifier: BSD-3-Clause
   * Copyright(c) 2010-2014 Intel Corporation
   */
  
  #include <stdio.h>
  #include <sys/queue.h>
  #include <string.h>
  #include <rte_mbuf.h>
  #include <rte_memory.h>
  #include <rte_memzone.h>
  #include <rte_errno.h>
  #include <rte_compat.h>
  #include <rte_string_fns.h>
  #include <rte_eal_memconfig.h>
  #include <rte_pause.h>
  #include <rte_tailq.h>
  
  #include "rte_distributor_v20.h"
  #include "rte_distributor_private.h"
  
  TAILQ_HEAD(rte_distributor_list, rte_distributor_v20);
  
  static struct rte_tailq_elem rte_distributor_tailq = {
  	.name = "RTE_DISTRIBUTOR",
  };
  EAL_REGISTER_TAILQ(rte_distributor_tailq)
  
  /**** APIs called by workers ****/
  
  void
  rte_distributor_request_pkt_v20(struct rte_distributor_v20 *d,
  		unsigned worker_id, struct rte_mbuf *oldpkt)
  {
  	union rte_distributor_buffer_v20 *buf = &d->bufs[worker_id];
  	int64_t req = (((int64_t)(uintptr_t)oldpkt) << RTE_DISTRIB_FLAG_BITS)
  			| RTE_DISTRIB_GET_BUF;
  	while (unlikely(buf->bufptr64 & RTE_DISTRIB_FLAGS_MASK))
  		rte_pause();
  	buf->bufptr64 = req;
  }
  VERSION_SYMBOL(rte_distributor_request_pkt, _v20, 2.0);
  
  struct rte_mbuf *
  rte_distributor_poll_pkt_v20(struct rte_distributor_v20 *d,
  		unsigned worker_id)
  {
  	union rte_distributor_buffer_v20 *buf = &d->bufs[worker_id];
  	if (buf->bufptr64 & RTE_DISTRIB_GET_BUF)
  		return NULL;
  
  	/* since bufptr64 is signed, this should be an arithmetic shift */
  	int64_t ret = buf->bufptr64 >> RTE_DISTRIB_FLAG_BITS;
  	return (struct rte_mbuf *)((uintptr_t)ret);
  }
  VERSION_SYMBOL(rte_distributor_poll_pkt, _v20, 2.0);
  
  struct rte_mbuf *
  rte_distributor_get_pkt_v20(struct rte_distributor_v20 *d,
  		unsigned worker_id, struct rte_mbuf *oldpkt)
  {
  	struct rte_mbuf *ret;
  	rte_distributor_request_pkt_v20(d, worker_id, oldpkt);
  	while ((ret = rte_distributor_poll_pkt_v20(d, worker_id)) == NULL)
  		rte_pause();
  	return ret;
  }
  VERSION_SYMBOL(rte_distributor_get_pkt, _v20, 2.0);
  
  int
  rte_distributor_return_pkt_v20(struct rte_distributor_v20 *d,
  		unsigned worker_id, struct rte_mbuf *oldpkt)
  {
  	union rte_distributor_buffer_v20 *buf = &d->bufs[worker_id];
  	uint64_t req = (((int64_t)(uintptr_t)oldpkt) << RTE_DISTRIB_FLAG_BITS)
  			| RTE_DISTRIB_RETURN_BUF;
  	buf->bufptr64 = req;
  	return 0;
  }
  VERSION_SYMBOL(rte_distributor_return_pkt, _v20, 2.0);
  
  /**** APIs called on distributor core ***/
  
  /* as name suggests, adds a packet to the backlog for a particular worker */
  static int
  add_to_backlog(struct rte_distributor_backlog *bl, int64_t item)
  {
  	if (bl->count == RTE_DISTRIB_BACKLOG_SIZE)
  		return -1;
  
  	bl->pkts[(bl->start + bl->count++) & (RTE_DISTRIB_BACKLOG_MASK)]
  			= item;
  	return 0;
  }
  
  /* takes the next packet for a worker off the backlog */
  static int64_t
  backlog_pop(struct rte_distributor_backlog *bl)
  {
  	bl->count--;
  	return bl->pkts[bl->start++ & RTE_DISTRIB_BACKLOG_MASK];
  }
  
  /* stores a packet returned from a worker inside the returns array */
  static inline void
  store_return(uintptr_t oldbuf, struct rte_distributor_v20 *d,
  		unsigned *ret_start, unsigned *ret_count)
  {
  	/* store returns in a circular buffer - code is branch-free */
  	d->returns.mbufs[(*ret_start + *ret_count) & RTE_DISTRIB_RETURNS_MASK]
  			= (void *)oldbuf;
  	*ret_start += (*ret_count == RTE_DISTRIB_RETURNS_MASK) & !!(oldbuf);
  	*ret_count += (*ret_count != RTE_DISTRIB_RETURNS_MASK) & !!(oldbuf);
  }
  
  static inline void
  handle_worker_shutdown(struct rte_distributor_v20 *d, unsigned int wkr)
  {
  	d->in_flight_tags[wkr] = 0;
  	d->in_flight_bitmask &= ~(1UL << wkr);
  	d->bufs[wkr].bufptr64 = 0;
  	if (unlikely(d->backlog[wkr].count != 0)) {
  		/* On return of a packet, we need to move the
  		 * queued packets for this core elsewhere.
  		 * Easiest solution is to set things up for
  		 * a recursive call. That will cause those
  		 * packets to be queued up for the next free
  		 * core, i.e. it will return as soon as a
  		 * core becomes free to accept the first
  		 * packet, as subsequent ones will be added to
  		 * the backlog for that core.
  		 */
  		struct rte_mbuf *pkts[RTE_DISTRIB_BACKLOG_SIZE];
  		unsigned i;
  		struct rte_distributor_backlog *bl = &d->backlog[wkr];
  
  		for (i = 0; i < bl->count; i++) {
  			unsigned idx = (bl->start + i) &
  					RTE_DISTRIB_BACKLOG_MASK;
  			pkts[i] = (void *)((uintptr_t)(bl->pkts[idx] >>
  					RTE_DISTRIB_FLAG_BITS));
  		}
  		/* recursive call.
  		 * Note that the tags were set before first level call
  		 * to rte_distributor_process.
  		 */
  		rte_distributor_process_v20(d, pkts, i);
  		bl->count = bl->start = 0;
  	}
  }
  
  /* this function is called when process() fn is called without any new
   * packets. It goes through all the workers and clears any returned packets
   * to do a partial flush.
   */
  static int
  process_returns(struct rte_distributor_v20 *d)
  {
  	unsigned wkr;
  	unsigned flushed = 0;
  	unsigned ret_start = d->returns.start,
  			ret_count = d->returns.count;
  
  	for (wkr = 0; wkr < d->num_workers; wkr++) {
  
  		const int64_t data = d->bufs[wkr].bufptr64;
  		uintptr_t oldbuf = 0;
  
  		if (data & RTE_DISTRIB_GET_BUF) {
  			flushed++;
  			if (d->backlog[wkr].count)
  				d->bufs[wkr].bufptr64 =
  						backlog_pop(&d->backlog[wkr]);
  			else {
  				d->bufs[wkr].bufptr64 = RTE_DISTRIB_GET_BUF;
  				d->in_flight_tags[wkr] = 0;
  				d->in_flight_bitmask &= ~(1UL << wkr);
  			}
  			oldbuf = data >> RTE_DISTRIB_FLAG_BITS;
  		} else if (data & RTE_DISTRIB_RETURN_BUF) {
  			handle_worker_shutdown(d, wkr);
  			oldbuf = data >> RTE_DISTRIB_FLAG_BITS;
  		}
  
  		store_return(oldbuf, d, &ret_start, &ret_count);
  	}
  
  	d->returns.start = ret_start;
  	d->returns.count = ret_count;
  
  	return flushed;
  }
  
  /* process a set of packets to distribute them to workers */
  int
  rte_distributor_process_v20(struct rte_distributor_v20 *d,
  		struct rte_mbuf **mbufs, unsigned num_mbufs)
  {
  	unsigned next_idx = 0;
  	unsigned wkr = 0;
  	struct rte_mbuf *next_mb = NULL;
  	int64_t next_value = 0;
  	uint32_t new_tag = 0;
  	unsigned ret_start = d->returns.start,
  			ret_count = d->returns.count;
  
  	if (unlikely(num_mbufs == 0))
  		return process_returns(d);
  
  	while (next_idx < num_mbufs || next_mb != NULL) {
  
  		int64_t data = d->bufs[wkr].bufptr64;
  		uintptr_t oldbuf = 0;
  
  		if (!next_mb) {
  			next_mb = mbufs[next_idx++];
  			next_value = (((int64_t)(uintptr_t)next_mb)
  					<< RTE_DISTRIB_FLAG_BITS);
  			/*
  			 * User is advocated to set tag value for each
  			 * mbuf before calling rte_distributor_process.
  			 * User defined tags are used to identify flows,
  			 * or sessions.
  			 */
  			new_tag = next_mb->hash.usr;
  
  			/*
  			 * Note that if RTE_DISTRIB_MAX_WORKERS is larger than 64
  			 * then the size of match has to be expanded.
  			 */
  			uint64_t match = 0;
  			unsigned i;
  			/*
  			 * to scan for a match use "xor" and "not" to get a 0/1
  			 * value, then use shifting to merge to single "match"
  			 * variable, where a one-bit indicates a match for the
  			 * worker given by the bit-position
  			 */
  			for (i = 0; i < d->num_workers; i++)
  				match |= (!(d->in_flight_tags[i] ^ new_tag)
  					<< i);
  
  			/* Only turned-on bits are considered as match */
  			match &= d->in_flight_bitmask;
  
  			if (match) {
  				next_mb = NULL;
  				unsigned worker = __builtin_ctzl(match);
  				if (add_to_backlog(&d->backlog[worker],
  						next_value) < 0)
  					next_idx--;
  			}
  		}
  
  		if ((data & RTE_DISTRIB_GET_BUF) &&
  				(d->backlog[wkr].count || next_mb)) {
  
  			if (d->backlog[wkr].count)
  				d->bufs[wkr].bufptr64 =
  						backlog_pop(&d->backlog[wkr]);
  
  			else {
  				d->bufs[wkr].bufptr64 = next_value;
  				d->in_flight_tags[wkr] = new_tag;
  				d->in_flight_bitmask |= (1UL << wkr);
  				next_mb = NULL;
  			}
  			oldbuf = data >> RTE_DISTRIB_FLAG_BITS;
  		} else if (data & RTE_DISTRIB_RETURN_BUF) {
  			handle_worker_shutdown(d, wkr);
  			oldbuf = data >> RTE_DISTRIB_FLAG_BITS;
  		}
  
  		/* store returns in a circular buffer */
  		store_return(oldbuf, d, &ret_start, &ret_count);
  
  		if (++wkr == d->num_workers)
  			wkr = 0;
  	}
  	/* to finish, check all workers for backlog and schedule work for them
  	 * if they are ready */
  	for (wkr = 0; wkr < d->num_workers; wkr++)
  		if (d->backlog[wkr].count &&
  				(d->bufs[wkr].bufptr64 & RTE_DISTRIB_GET_BUF)) {
  
  			int64_t oldbuf = d->bufs[wkr].bufptr64 >>
  					RTE_DISTRIB_FLAG_BITS;
  			store_return(oldbuf, d, &ret_start, &ret_count);
  
  			d->bufs[wkr].bufptr64 = backlog_pop(&d->backlog[wkr]);
  		}
  
  	d->returns.start = ret_start;
  	d->returns.count = ret_count;
  	return num_mbufs;
  }
  VERSION_SYMBOL(rte_distributor_process, _v20, 2.0);
  
  /* return to the caller, packets returned from workers */
  int
  rte_distributor_returned_pkts_v20(struct rte_distributor_v20 *d,
  		struct rte_mbuf **mbufs, unsigned max_mbufs)
  {
  	struct rte_distributor_returned_pkts *returns = &d->returns;
  	unsigned retval = (max_mbufs < returns->count) ?
  			max_mbufs : returns->count;
  	unsigned i;
  
  	for (i = 0; i < retval; i++) {
  		unsigned idx = (returns->start + i) & RTE_DISTRIB_RETURNS_MASK;
  		mbufs[i] = returns->mbufs[idx];
  	}
  	returns->start += i;
  	returns->count -= i;
  
  	return retval;
  }
  VERSION_SYMBOL(rte_distributor_returned_pkts, _v20, 2.0);
  
  /* return the number of packets in-flight in a distributor, i.e. packets
   * being worked on or queued up in a backlog.
   */
  static inline unsigned
  total_outstanding(const struct rte_distributor_v20 *d)
  {
  	unsigned wkr, total_outstanding;
  
  	total_outstanding = __builtin_popcountl(d->in_flight_bitmask);
  
  	for (wkr = 0; wkr < d->num_workers; wkr++)
  		total_outstanding += d->backlog[wkr].count;
  
  	return total_outstanding;
  }
  
  /* flush the distributor, so that there are no outstanding packets in flight or
   * queued up. */
  int
  rte_distributor_flush_v20(struct rte_distributor_v20 *d)
  {
  	const unsigned flushed = total_outstanding(d);
  
  	while (total_outstanding(d) > 0)
  		rte_distributor_process_v20(d, NULL, 0);
  
  	return flushed;
  }
  VERSION_SYMBOL(rte_distributor_flush, _v20, 2.0);
  
  /* clears the internal returns array in the distributor */
  void
  rte_distributor_clear_returns_v20(struct rte_distributor_v20 *d)
  {
  	d->returns.start = d->returns.count = 0;
  #ifndef __OPTIMIZE__
  	memset(d->returns.mbufs, 0, sizeof(d->returns.mbufs));
  #endif
  }
  VERSION_SYMBOL(rte_distributor_clear_returns, _v20, 2.0);
  
  /* creates a distributor instance */
  struct rte_distributor_v20 *
  rte_distributor_create_v20(const char *name,
  		unsigned socket_id,
  		unsigned num_workers)
  {
  	struct rte_distributor_v20 *d;
  	struct rte_distributor_list *distributor_list;
  	char mz_name[RTE_MEMZONE_NAMESIZE];
  	const struct rte_memzone *mz;
  
  	/* compilation-time checks */
  	RTE_BUILD_BUG_ON((sizeof(*d) & RTE_CACHE_LINE_MASK) != 0);
  	RTE_BUILD_BUG_ON((RTE_DISTRIB_MAX_WORKERS & 7) != 0);
  	RTE_BUILD_BUG_ON(RTE_DISTRIB_MAX_WORKERS >
  				sizeof(d->in_flight_bitmask) * CHAR_BIT);
  
  	if (name == NULL || num_workers >= RTE_DISTRIB_MAX_WORKERS) {
  		rte_errno = EINVAL;
  		return NULL;
  	}
  
  	snprintf(mz_name, sizeof(mz_name), RTE_DISTRIB_PREFIX"%s", name);
  	mz = rte_memzone_reserve(mz_name, sizeof(*d), socket_id, NO_FLAGS);
  	if (mz == NULL) {
  		rte_errno = ENOMEM;
  		return NULL;
  	}
  
  	d = mz->addr;
  	strlcpy(d->name, name, sizeof(d->name));
  	d->num_workers = num_workers;
  
  	distributor_list = RTE_TAILQ_CAST(rte_distributor_tailq.head,
  					  rte_distributor_list);
  
  	rte_mcfg_tailq_write_lock();
  	TAILQ_INSERT_TAIL(distributor_list, d, next);
  	rte_mcfg_tailq_write_unlock();
  
  	return d;
  }
  VERSION_SYMBOL(rte_distributor_create, _v20, 2.0);
  