DPDK 22.11.6
rte_ring_hts_elem_pvt.h
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1/* SPDX-License-Identifier: BSD-3-Clause
2 *
3 * Copyright (c) 2010-2020 Intel Corporation
4 * Copyright (c) 2007-2009 Kip Macy kmacy@freebsd.org
5 * All rights reserved.
6 * Derived from FreeBSD's bufring.h
7 * Used as BSD-3 Licensed with permission from Kip Macy.
8 */
9
10#ifndef _RTE_RING_HTS_ELEM_PVT_H_
11#define _RTE_RING_HTS_ELEM_PVT_H_
12
24static __rte_always_inline void
25__rte_ring_hts_update_tail(struct rte_ring_hts_headtail *ht, uint32_t old_tail,
26 uint32_t num, uint32_t enqueue)
27{
28 uint32_t tail;
29
30 RTE_SET_USED(enqueue);
31
32 tail = old_tail + num;
33 __atomic_store_n(&ht->ht.pos.tail, tail, __ATOMIC_RELEASE);
34}
35
41static __rte_always_inline void
42__rte_ring_hts_head_wait(const struct rte_ring_hts_headtail *ht,
43 union __rte_ring_hts_pos *p)
44{
45 while (p->pos.head != p->pos.tail) {
46 rte_pause();
47 p->raw = __atomic_load_n(&ht->ht.raw, __ATOMIC_ACQUIRE);
48 }
49}
50
54static __rte_always_inline unsigned int
55__rte_ring_hts_move_prod_head(struct rte_ring *r, unsigned int num,
56 enum rte_ring_queue_behavior behavior, uint32_t *old_head,
57 uint32_t *free_entries)
58{
59 uint32_t n;
60 union __rte_ring_hts_pos np, op;
61
62 const uint32_t capacity = r->capacity;
63
64 op.raw = __atomic_load_n(&r->hts_prod.ht.raw, __ATOMIC_ACQUIRE);
65
66 do {
67 /* Reset n to the initial burst count */
68 n = num;
69
70 /*
71 * wait for tail to be equal to head,
72 * make sure that we read prod head/tail *before*
73 * reading cons tail.
74 */
75 __rte_ring_hts_head_wait(&r->hts_prod, &op);
76
77 /*
78 * The subtraction is done between two unsigned 32bits value
79 * (the result is always modulo 32 bits even if we have
80 * *old_head > cons_tail). So 'free_entries' is always between 0
81 * and capacity (which is < size).
82 */
83 *free_entries = capacity + r->cons.tail - op.pos.head;
84
85 /* check that we have enough room in ring */
86 if (unlikely(n > *free_entries))
87 n = (behavior == RTE_RING_QUEUE_FIXED) ?
88 0 : *free_entries;
89
90 if (n == 0)
91 break;
92
93 np.pos.tail = op.pos.tail;
94 np.pos.head = op.pos.head + n;
95
96 /*
97 * this CAS(ACQUIRE, ACQUIRE) serves as a hoist barrier to prevent:
98 * - OOO reads of cons tail value
99 * - OOO copy of elems from the ring
100 */
101 } while (__atomic_compare_exchange_n(&r->hts_prod.ht.raw,
102 &op.raw, np.raw,
103 0, __ATOMIC_ACQUIRE, __ATOMIC_ACQUIRE) == 0);
104
105 *old_head = op.pos.head;
106 return n;
107}
108
112static __rte_always_inline unsigned int
113__rte_ring_hts_move_cons_head(struct rte_ring *r, unsigned int num,
114 enum rte_ring_queue_behavior behavior, uint32_t *old_head,
115 uint32_t *entries)
116{
117 uint32_t n;
118 union __rte_ring_hts_pos np, op;
119
120 op.raw = __atomic_load_n(&r->hts_cons.ht.raw, __ATOMIC_ACQUIRE);
121
122 /* move cons.head atomically */
123 do {
124 /* Restore n as it may change every loop */
125 n = num;
126
127 /*
128 * wait for tail to be equal to head,
129 * make sure that we read cons head/tail *before*
130 * reading prod tail.
131 */
132 __rte_ring_hts_head_wait(&r->hts_cons, &op);
133
134 /* The subtraction is done between two unsigned 32bits value
135 * (the result is always modulo 32 bits even if we have
136 * cons_head > prod_tail). So 'entries' is always between 0
137 * and size(ring)-1.
138 */
139 *entries = r->prod.tail - op.pos.head;
140
141 /* Set the actual entries for dequeue */
142 if (n > *entries)
143 n = (behavior == RTE_RING_QUEUE_FIXED) ? 0 : *entries;
144
145 if (unlikely(n == 0))
146 break;
147
148 np.pos.tail = op.pos.tail;
149 np.pos.head = op.pos.head + n;
150
151 /*
152 * this CAS(ACQUIRE, ACQUIRE) serves as a hoist barrier to prevent:
153 * - OOO reads of prod tail value
154 * - OOO copy of elems from the ring
155 */
156 } while (__atomic_compare_exchange_n(&r->hts_cons.ht.raw,
157 &op.raw, np.raw,
158 0, __ATOMIC_ACQUIRE, __ATOMIC_ACQUIRE) == 0);
159
160 *old_head = op.pos.head;
161 return n;
162}
163
186static __rte_always_inline unsigned int
187__rte_ring_do_hts_enqueue_elem(struct rte_ring *r, const void *obj_table,
188 uint32_t esize, uint32_t n, enum rte_ring_queue_behavior behavior,
189 uint32_t *free_space)
190{
191 uint32_t free, head;
192
193 n = __rte_ring_hts_move_prod_head(r, n, behavior, &head, &free);
194
195 if (n != 0) {
196 __rte_ring_enqueue_elems(r, head, obj_table, esize, n);
197 __rte_ring_hts_update_tail(&r->hts_prod, head, n, 1);
198 }
199
200 if (free_space != NULL)
201 *free_space = free - n;
202 return n;
203}
204
227static __rte_always_inline unsigned int
228__rte_ring_do_hts_dequeue_elem(struct rte_ring *r, void *obj_table,
229 uint32_t esize, uint32_t n, enum rte_ring_queue_behavior behavior,
230 uint32_t *available)
231{
232 uint32_t entries, head;
233
234 n = __rte_ring_hts_move_cons_head(r, n, behavior, &head, &entries);
235
236 if (n != 0) {
237 __rte_ring_dequeue_elems(r, head, obj_table, esize, n);
238 __rte_ring_hts_update_tail(&r->hts_cons, head, n, 0);
239 }
240
241 if (available != NULL)
242 *available = entries - n;
243 return n;
244}
245
246#endif /* _RTE_RING_HTS_ELEM_PVT_H_ */
#define unlikely(x)
#define RTE_SET_USED(x)
Definition: rte_common.h:135
#define __rte_always_inline
Definition: rte_common.h:255
static void rte_pause(void)
rte_ring_queue_behavior
Definition: rte_ring_core.h:43
@ RTE_RING_QUEUE_FIXED
Definition: rte_ring_core.h:45
volatile uint32_t tail
Definition: rte_ring_core.h:70
uint32_t capacity