ib_ring.c revision 12763:4b30642bc04e 
1/*
2 * Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
3 */
4
5/*
6 * This file contains code imported from the OFED rds source file ib_ring.c
7 * Oracle elects to have and use the contents of ib_ring.c under and governed
8 * by the OpenIB.org BSD license (see below for full license text). However,
9 * the following notice accompanied the original version of this file:
10 */
11
12/*
13 * Copyright (c) 2006 Oracle.  All rights reserved.
14 *
15 * This software is available to you under a choice of one of two
16 * licenses.  You may choose to be licensed under the terms of the GNU
17 * General Public License (GPL) Version 2, available from the file
18 * COPYING in the main directory of this source tree, or the
19 * OpenIB.org BSD license below:
20 *
21 *     Redistribution and use in source and binary forms, with or
22 *     without modification, are permitted provided that the following
23 *     conditions are met:
24 *
25 *      - Redistributions of source code must retain the above
26 *        copyright notice, this list of conditions and the following
27 *        disclaimer.
28 *
29 *      - Redistributions in binary form must reproduce the above
30 *        copyright notice, this list of conditions and the following
31 *        disclaimer in the documentation and/or other materials
32 *        provided with the distribution.
33 *
34 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
35 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
36 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
37 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
38 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
39 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
40 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
41 * SOFTWARE.
42 *
43 */
44#include <sys/rds.h>
45
46#include <sys/ib/clients/rdsv3/rdsv3.h>
47#include <sys/ib/clients/rdsv3/ib.h>
48#include <sys/ib/clients/rdsv3/rdsv3_debug.h>
49
50/*
51 * Locking for IB rings.
52 * We assume that allocation is always protected by a mutex
53 * in the caller (this is a valid assumption for the current
54 * implementation).
55 *
56 * Freeing always happens in an interrupt, and hence only
57 * races with allocations, but not with other free()s.
58 *
59 * The interaction between allocation and freeing is that
60 * the alloc code has to determine the number of free entries.
61 * To this end, we maintain two counters; an allocation counter
62 * and a free counter. Both are allowed to run freely, and wrap
63 * around.
64 * The number of used entries is always (alloc_ctr - free_ctr) % NR.
65 *
66 * The current implementation makes free_ctr atomic. When the
67 * caller finds an allocation fails, it should set an "alloc fail"
68 * bit and retry the allocation. The "alloc fail" bit essentially tells
69 * the CQ completion handlers to wake it up after freeing some
70 * more entries.
71 */
72
73void
74rdsv3_ib_ring_init(struct rdsv3_ib_work_ring *ring, uint32_t nr)
75{
76	(void) memset(ring, 0, sizeof (*ring));
77	ring->w_nr = nr;
78	RDSV3_DPRINTF5("rdsv3_ib_ring_init", "ring %p nr %u", ring, ring->w_nr);
79}
80
81static inline uint32_t
82__rdsv3_ib_ring_used(struct rdsv3_ib_work_ring *ring)
83{
84	uint32_t diff;
85
86	/* This assumes that atomic_t has at least as many bits as uint32_t */
87	diff = ring->w_alloc_ctr - (uint32_t)atomic_get(&ring->w_free_ctr);
88	ASSERT(diff <= ring->w_nr);
89
90	return (diff);
91}
92
93void
94rdsv3_ib_ring_resize(struct rdsv3_ib_work_ring *ring, uint32_t nr)
95{
96	/*
97	 * We only ever get called from the connection setup code,
98	 * prior to creating the QP.
99	 */
100	ASSERT(!__rdsv3_ib_ring_used(ring));
101	ring->w_nr = nr;
102}
103
104static int
105__rdsv3_ib_ring_empty(struct rdsv3_ib_work_ring *ring)
106{
107	return (__rdsv3_ib_ring_used(ring) == 0);
108}
109
110uint32_t
111rdsv3_ib_ring_alloc(struct rdsv3_ib_work_ring *ring, uint32_t val,
112    uint32_t *pos)
113{
114	uint32_t ret = 0, avail;
115
116	avail = ring->w_nr - __rdsv3_ib_ring_used(ring);
117
118	RDSV3_DPRINTF5("rdsv3_ib_ring_alloc",
119	    "ring %p val %u next %u free %u", ring, val,
120	    ring->w_alloc_ptr, avail);
121
122	if (val && avail) {
123		ret = min(val, avail);
124		*pos = ring->w_alloc_ptr;
125
126		ring->w_alloc_ptr = (ring->w_alloc_ptr + ret) % ring->w_nr;
127		ring->w_alloc_ctr += ret;
128	}
129
130	return (ret);
131}
132
133void
134rdsv3_ib_ring_free(struct rdsv3_ib_work_ring *ring, uint32_t val)
135{
136	ring->w_free_ptr = (ring->w_free_ptr + val) % ring->w_nr;
137	atomic_add_32(&ring->w_free_ctr, val);
138
139	if (__rdsv3_ib_ring_empty(ring))
140		rdsv3_wake_up(&ring->w_empty_wait);
141}
142
143void
144rdsv3_ib_ring_unalloc(struct rdsv3_ib_work_ring *ring, uint32_t val)
145{
146	ring->w_alloc_ptr = (ring->w_alloc_ptr - val) % ring->w_nr;
147	ring->w_alloc_ctr -= val;
148}
149
150int
151rdsv3_ib_ring_empty(struct rdsv3_ib_work_ring *ring)
152{
153	return (__rdsv3_ib_ring_empty(ring));
154}
155
156int
157rdsv3_ib_ring_low(struct rdsv3_ib_work_ring *ring)
158{
159	return (__rdsv3_ib_ring_used(ring) <= (ring->w_nr >> 2));
160}
161
162/*
163 * returns the oldest alloced ring entry.  This will be the next one
164 * freed.  This can't be called if there are none allocated.
165 */
166uint32_t
167rdsv3_ib_ring_oldest(struct rdsv3_ib_work_ring *ring)
168{
169	return (ring->w_free_ptr);
170}
171
172/*
173 * returns the number of completed work requests.
174 */
175
176uint32_t
177rdsv3_ib_ring_completed(struct rdsv3_ib_work_ring *ring,
178    uint32_t wr_id, uint32_t oldest)
179{
180	uint32_t ret;
181
182	if (oldest <= (unsigned long long)wr_id)
183		ret = (unsigned long long)wr_id - oldest + 1;
184	else
185		ret = ring->w_nr - oldest + (unsigned long long)wr_id + 1;
186
187	RDSV3_DPRINTF5("rdsv3_ib_ring_completed",
188	    "ring %p ret %u wr_id %u oldest %u", ring, ret, wr_id, oldest);
189	return (ret);
190}
191