src/svm/svm_fifo.h

/*
 * Copyright (c) 2016 Cisco and/or its affiliates.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at:
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#ifndef __included_ssvm_fifo_h__
#define __included_ssvm_fifo_h__

#include <vppinfra/clib.h>
#include <vppinfra/vec.h>
#include <vppinfra/mheap.h>
#include <vppinfra/heap.h>
#include <vppinfra/pool.h>
#include <vppinfra/format.h>
#include <pthread.h>

/** Out-of-order segment */
typedef struct
{
  u32 next;	/**< Next linked-list element pool index */
  u32 prev;	/**< Previous linked-list element pool index */

  u32 start;	/**< Start of segment, normalized*/
  u32 length;	/**< Length of segment */
} ooo_segment_t;

format_function_t format_ooo_segment;
format_function_t format_ooo_list;

#define SVM_FIFO_TRACE 			(0)
#define OOO_SEGMENT_INVALID_INDEX 	((u32)~0)
#define SVM_FIFO_INVALID_SESSION_INDEX 	((u32)~0)
#define SVM_FIFO_INVALID_INDEX		((u32)~0)
#define SVM_FIFO_MAX_EVT_SUBSCRIBERS	8

enum
{
  SVM_FIFO_NO_TX_NOTIF = 0,
  SVM_FIFO_WANT_TX_NOTIF = 1,
  SVM_FIFO_WANT_TX_NOTIF_IF_FULL = 2,
};

typedef struct
{
  u32 offset;
  u32 len;
  u32 action;
} svm_fifo_trace_elem_t;

typedef struct _svm_fifo
{
  CLIB_CACHE_LINE_ALIGN_MARK (shared_first);
  volatile u32 cursize;		/**< current fifo size */
  u32 nitems;

    CLIB_CACHE_LINE_ALIGN_MARK (shared_second);
  volatile u32 has_event;	/**< non-zero if deq event exists */

  u32 master_session_index;
  u32 client_session_index;
  u8 master_thread_index;
  u8 client_thread_index;
  u32 segment_manager;
  u32 segment_index;
  u32 ct_session_index;		/**< Local session index for vpp */
  u32 freelist_index;		/**< aka log2(allocated_size) - const. */
  i8 refcnt;			/**< reference count  */

    CLIB_CACHE_LINE_ALIGN_MARK (consumer);
  u32 head;
  volatile u32 want_tx_ntf;	/**< producer wants nudge */
  volatile u32 has_tx_ntf;

    CLIB_CACHE_LINE_ALIGN_MARK (producer);
  u32 tail;

  ooo_segment_t *ooo_segments;	/**< Pool of ooo segments */
  u32 ooos_list_head;		/**< Head of out-of-order linked-list */
  u32 ooos_newest;		/**< Last segment to have been updated */
  struct _svm_fifo *next;	/**< next in freelist/active chain */
  struct _svm_fifo *prev;	/**< prev in active chain */
  volatile u8 n_subscribers;
  u8 subscribers[SVM_FIFO_MAX_EVT_SUBSCRIBERS];

#if SVM_FIFO_TRACE
  svm_fifo_trace_elem_t *trace;
#endif

    CLIB_CACHE_LINE_ALIGN_MARK (data);
} svm_fifo_t;

typedef enum
{
  SVM_FIFO_FULL = -2,
} svm_fifo_err_t;

typedef struct svm_fifo_segment_
{
  u8 *data;
  u32 len;
} svm_fifo_segment_t;

#if SVM_FIFO_TRACE
#define svm_fifo_trace_add(_f, _s, _l, _t)		\
{							\
  svm_fifo_trace_elem_t *trace_elt;			\
  vec_add2(_f->trace, trace_elt, 1);			\
  trace_elt->offset = _s;				\
  trace_elt->len = _l;					\
  trace_elt->action = _t;				\
}
#else
#define svm_fifo_trace_add(_f, _s, _l, _t)
#endif

u8 *svm_fifo_dump_trace (u8 * s, svm_fifo_t * f);
u8 *svm_fifo_replay (u8 * s, svm_fifo_t * f, u8 no_read, u8 verbose);

static inline u32
svm_fifo_max_dequeue (svm_fifo_t * f)
{
  return clib_atomic_load_acq_n (&f->cursize);
}

static inline int
svm_fifo_is_full (svm_fifo_t * f)
{
  return (clib_atomic_load_acq_n (&f->cursize) == f->nitems);
}

static inline int
svm_fifo_is_empty (svm_fifo_t * f)
{
  return (clib_atomic_load_acq_n (&f->cursize) == 0);
}

static inline u32
svm_fifo_max_enqueue (svm_fifo_t * f)
{
  return f->nitems - svm_fifo_max_dequeue (f);
}

static inline int
svm_fifo_has_event (svm_fifo_t * f)
{
  return f->has_event;
}

static inline u8
svm_fifo_has_ooo_data (svm_fifo_t * f)
{
  return f->ooos_list_head != OOO_SEGMENT_INVALID_INDEX;
}

/**
 * Sets fifo event flag.
 *
 * Also acts as a release barrier.
 *
 * @return 1 if flag was not set.
 */
always_inline u8
svm_fifo_set_event (svm_fifo_t * f)
{
  /* return __sync_lock_test_and_set (&f->has_event, 1) == 0;
     return __sync_bool_compare_and_swap (&f->has_event, 0, 1); */
  return !__atomic_exchange_n (&f->has_event, 1, __ATOMIC_RELEASE);
}

/**
 * Unsets fifo event flag.
 *
 * Also acts as a release barrier.
 */
always_inline void
svm_fifo_unset_event (svm_fifo_t * f)
{
  clib_atomic_release (&f->has_event);
}

svm_fifo_t *svm_fifo_create (u32 data_size_in_bytes);
void svm_fifo_free (svm_fifo_t * f);

int svm_fifo_enqueue_nowait (svm_fifo_t * f, u32 max_bytes,
			     const u8 * copy_from_here);
int svm_fifo_enqueue_with_offset (svm_fifo_t * f, u32 offset,
				  u32 required_bytes, u8 * copy_from_here);
int svm_fifo_dequeue_nowait (svm_fifo_t * f, u32 max_bytes, u8 * copy_here);

int svm_fifo_peek (svm_fifo_t * f, u32 offset, u32 max_bytes, u8 * copy_here);
int svm_fifo_dequeue_drop (svm_fifo_t * f, u32 max_bytes);
void svm_fifo_dequeue_drop_all (svm_fifo_t * f);
int svm_fifo_segments (svm_fifo_t * f, svm_fifo_segment_t * fs);
void svm_fifo_segments_free (svm_fifo_t * f, svm_fifo_segment_t * fs);
void svm_fifo_init_pointers (svm_fifo_t * f, u32 pointer);
void svm_fifo_overwrite_head (svm_fifo_t * f, u8 * data, u32 len);
void svm_fifo_add_subscriber (svm_fifo_t * f, u8 subscriber);
void svm_fifo_del_subscriber (svm_fifo_t * f, u8 subscriber);
format_function_t format_svm_fifo;

/**
 * Max contiguous chunk of data that can be read
 */
always_inline u32
svm_fifo_max_read_chunk (svm_fifo_t * f)
{
  return ((f->tail > f->head) ? (f->tail - f->head) : (f->nitems - f->head));
}

/**
 * Max contiguous chunk of data that can be written
 */
always_inline u32
svm_fifo_max_write_chunk (svm_fifo_t * f)
{
  return ((f->tail >= f->head) ? (f->nitems - f->tail) : (f->head - f->tail));
}

/**
 * Advance tail pointer
 *
 * Useful for moving tail pointer after external enqueue.
 */
always_inline void
svm_fifo_enqueue_nocopy (svm_fifo_t * f, u32 bytes)
{
  ASSERT (bytes <= svm_fifo_max_enqueue (f));
  f->tail = (f->tail + bytes) % f->nitems;
  clib_atomic_fetch_add_rel (&f->cursize, bytes);
}

always_inline u8 *
svm_fifo_head (svm_fifo_t * f)
{
  return (f->data + f->head);
}

always_inline u8 *
svm_fifo_tail (svm_fifo_t * f)
{
  return (f->data + f->tail);
}

always_inline u32
svm_fifo_nitems (svm_fifo_t * f)
{
  return f->nitems;
}

static inline void
svm_fifo_add_want_tx_ntf (svm_fifo_t * f, u8 ntf_type)
{
  f->want_tx_ntf |= ntf_type;
}

static inline void
svm_fifo_del_want_tx_ntf (svm_fifo_t * f, u8 ntf_type)
{
  f->want_tx_ntf &= ~ntf_type;
}

static inline void
svm_fifo_clear_tx_ntf (svm_fifo_t * f)
{
  /* Set the flag if want_tx_notif_if_full was the only ntf requested */
  f->has_tx_ntf = f->want_tx_ntf == SVM_FIFO_WANT_TX_NOTIF_IF_FULL;
  svm_fifo_del_want_tx_ntf (f, SVM_FIFO_WANT_TX_NOTIF);
}

static inline void
svm_fifo_reset_tx_ntf (svm_fifo_t * f)
{
  f->has_tx_ntf = 0;
}

static inline u8
svm_fifo_needs_tx_ntf (svm_fifo_t * f, u32 n_last_deq)
{
  u8 want_ntf = f->want_tx_ntf;

  if (PREDICT_TRUE (want_ntf == SVM_FIFO_NO_TX_NOTIF))
    return 0;
  else if (want_ntf & SVM_FIFO_WANT_TX_NOTIF)
    return 1;
  else if (want_ntf & SVM_FIFO_WANT_TX_NOTIF_IF_FULL)
    {
      u32 max_deq = svm_fifo_max_dequeue (f);
      u32 nitems = svm_fifo_nitems (f);
      if (!f->has_tx_ntf && max_deq < nitems
	  && max_deq + n_last_deq >= nitems)
	return 1;

      return 0;
    }
  return 0;
}

always_inline u8
svm_fifo_n_subscribers (svm_fifo_t * f)
{
  return f->n_subscribers;
}

u32 svm_fifo_number_ooo_segments (svm_fifo_t * f);
ooo_segment_t *svm_fifo_first_ooo_segment (svm_fifo_t * f);

always_inline ooo_segment_t *
svm_fifo_newest_ooo_segment (svm_fifo_t * f)
{
  if (f->ooos_newest == OOO_SEGMENT_INVALID_INDEX)
    return 0;
  return pool_elt_at_index (f->ooo_segments, f->ooos_newest);
}

always_inline void
svm_fifo_newest_ooo_segment_reset (svm_fifo_t * f)
{
  f->ooos_newest = OOO_SEGMENT_INVALID_INDEX;
}

always_inline u32
ooo_segment_distance_from_tail (svm_fifo_t * f, u32 pos)
{
  /* Ambiguous. Assumption is that ooo segments don't touch tail */
  if (PREDICT_FALSE (pos == f->tail && f->tail == f->head))
    return f->nitems;

  return (((f->nitems + pos) - f->tail) % f->nitems);
}

always_inline u32
ooo_segment_distance_to_tail (svm_fifo_t * f, u32 pos)
{
  return (((f->nitems + f->tail) - pos) % f->nitems);
}

always_inline u32
ooo_segment_offset (svm_fifo_t * f, ooo_segment_t * s)
{
  return ooo_segment_distance_from_tail (f, s->start);
}

always_inline u32
ooo_segment_end_offset (svm_fifo_t * f, ooo_segment_t * s)
{
  return ooo_segment_distance_from_tail (f, s->start) + s->length;
}

always_inline u32
ooo_segment_length (svm_fifo_t * f, ooo_segment_t * s)
{
  return s->length;
}

always_inline ooo_segment_t *
ooo_segment_get_prev (svm_fifo_t * f, ooo_segment_t * s)
{
  if (s->prev == OOO_SEGMENT_INVALID_INDEX)
    return 0;
  return pool_elt_at_index (f->ooo_segments, s->prev);
}

always_inline ooo_segment_t *
ooo_segment_next (svm_fifo_t * f, ooo_segment_t * s)
{
  if (s->next == OOO_SEGMENT_INVALID_INDEX)
    return 0;
  return pool_elt_at_index (f->ooo_segments, s->next);
}

#endif /* __included_ssvm_fifo_h__ */

/*
 * fd.io coding-style-patch-verification: ON
 *
 * Local Variables:
 * eval: (c-set-style "gnu")
 * End:
 */