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1 | /* |
2 | * Copyright (c) 2006 Oracle. All rights reserved. | |
3 | * | |
4 | * This software is available to you under a choice of one of two | |
5 | * licenses. You may choose to be licensed under the terms of the GNU | |
6 | * General Public License (GPL) Version 2, available from the file | |
7 | * COPYING in the main directory of this source tree, or the | |
8 | * OpenIB.org BSD license below: | |
9 | * | |
10 | * Redistribution and use in source and binary forms, with or | |
11 | * without modification, are permitted provided that the following | |
12 | * conditions are met: | |
13 | * | |
14 | * - Redistributions of source code must retain the above | |
15 | * copyright notice, this list of conditions and the following | |
16 | * disclaimer. | |
17 | * | |
18 | * - Redistributions in binary form must reproduce the above | |
19 | * copyright notice, this list of conditions and the following | |
20 | * disclaimer in the documentation and/or other materials | |
21 | * provided with the distribution. | |
22 | * | |
23 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, | |
24 | * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF | |
25 | * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND | |
26 | * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS | |
27 | * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN | |
28 | * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN | |
29 | * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE | |
30 | * SOFTWARE. | |
31 | * | |
32 | */ | |
33 | #include <linux/kernel.h> | |
34 | ||
35 | #include "rds.h" | |
36 | #include "ib.h" | |
37 | ||
38 | /* | |
39 | * Locking for IB rings. | |
40 | * We assume that allocation is always protected by a mutex | |
41 | * in the caller (this is a valid assumption for the current | |
42 | * implementation). | |
43 | * | |
44 | * Freeing always happens in an interrupt, and hence only | |
45 | * races with allocations, but not with other free()s. | |
46 | * | |
47 | * The interaction between allocation and freeing is that | |
48 | * the alloc code has to determine the number of free entries. | |
49 | * To this end, we maintain two counters; an allocation counter | |
50 | * and a free counter. Both are allowed to run freely, and wrap | |
51 | * around. | |
52 | * The number of used entries is always (alloc_ctr - free_ctr) % NR. | |
53 | * | |
54 | * The current implementation makes free_ctr atomic. When the | |
55 | * caller finds an allocation fails, it should set an "alloc fail" | |
56 | * bit and retry the allocation. The "alloc fail" bit essentially tells | |
57 | * the CQ completion handlers to wake it up after freeing some | |
58 | * more entries. | |
59 | */ | |
60 | ||
61 | /* | |
62 | * This only happens on shutdown. | |
63 | */ | |
64 | DECLARE_WAIT_QUEUE_HEAD(rds_ib_ring_empty_wait); | |
65 | ||
66 | void rds_ib_ring_init(struct rds_ib_work_ring *ring, u32 nr) | |
67 | { | |
68 | memset(ring, 0, sizeof(*ring)); | |
69 | ring->w_nr = nr; | |
70 | rdsdebug("ring %p nr %u\n", ring, ring->w_nr); | |
71 | } | |
72 | ||
73 | static inline u32 __rds_ib_ring_used(struct rds_ib_work_ring *ring) | |
74 | { | |
75 | u32 diff; | |
76 | ||
77 | /* This assumes that atomic_t has at least as many bits as u32 */ | |
78 | diff = ring->w_alloc_ctr - (u32) atomic_read(&ring->w_free_ctr); | |
79 | BUG_ON(diff > ring->w_nr); | |
80 | ||
81 | return diff; | |
82 | } | |
83 | ||
84 | void rds_ib_ring_resize(struct rds_ib_work_ring *ring, u32 nr) | |
85 | { | |
86 | /* We only ever get called from the connection setup code, | |
87 | * prior to creating the QP. */ | |
88 | BUG_ON(__rds_ib_ring_used(ring)); | |
89 | ring->w_nr = nr; | |
90 | } | |
91 | ||
92 | static int __rds_ib_ring_empty(struct rds_ib_work_ring *ring) | |
93 | { | |
94 | return __rds_ib_ring_used(ring) == 0; | |
95 | } | |
96 | ||
97 | u32 rds_ib_ring_alloc(struct rds_ib_work_ring *ring, u32 val, u32 *pos) | |
98 | { | |
99 | u32 ret = 0, avail; | |
100 | ||
101 | avail = ring->w_nr - __rds_ib_ring_used(ring); | |
102 | ||
103 | rdsdebug("ring %p val %u next %u free %u\n", ring, val, | |
104 | ring->w_alloc_ptr, avail); | |
105 | ||
106 | if (val && avail) { | |
107 | ret = min(val, avail); | |
108 | *pos = ring->w_alloc_ptr; | |
109 | ||
110 | ring->w_alloc_ptr = (ring->w_alloc_ptr + ret) % ring->w_nr; | |
111 | ring->w_alloc_ctr += ret; | |
112 | } | |
113 | ||
114 | return ret; | |
115 | } | |
116 | ||
117 | void rds_ib_ring_free(struct rds_ib_work_ring *ring, u32 val) | |
118 | { | |
119 | ring->w_free_ptr = (ring->w_free_ptr + val) % ring->w_nr; | |
120 | atomic_add(val, &ring->w_free_ctr); | |
121 | ||
122 | if (__rds_ib_ring_empty(ring) && | |
123 | waitqueue_active(&rds_ib_ring_empty_wait)) | |
124 | wake_up(&rds_ib_ring_empty_wait); | |
125 | } | |
126 | ||
127 | void rds_ib_ring_unalloc(struct rds_ib_work_ring *ring, u32 val) | |
128 | { | |
129 | ring->w_alloc_ptr = (ring->w_alloc_ptr - val) % ring->w_nr; | |
130 | ring->w_alloc_ctr -= val; | |
131 | } | |
132 | ||
133 | int rds_ib_ring_empty(struct rds_ib_work_ring *ring) | |
134 | { | |
135 | return __rds_ib_ring_empty(ring); | |
136 | } | |
137 | ||
138 | int rds_ib_ring_low(struct rds_ib_work_ring *ring) | |
139 | { | |
140 | return __rds_ib_ring_used(ring) <= (ring->w_nr >> 2); | |
141 | } | |
142 | ||
143 | /* | |
144 | * returns the oldest alloced ring entry. This will be the next one | |
145 | * freed. This can't be called if there are none allocated. | |
146 | */ | |
147 | u32 rds_ib_ring_oldest(struct rds_ib_work_ring *ring) | |
148 | { | |
149 | return ring->w_free_ptr; | |
150 | } | |
151 | ||
152 | /* | |
153 | * returns the number of completed work requests. | |
154 | */ | |
155 | ||
156 | u32 rds_ib_ring_completed(struct rds_ib_work_ring *ring, u32 wr_id, u32 oldest) | |
157 | { | |
158 | u32 ret; | |
159 | ||
160 | if (oldest <= (unsigned long long)wr_id) | |
161 | ret = (unsigned long long)wr_id - oldest + 1; | |
162 | else | |
163 | ret = ring->w_nr - oldest + (unsigned long long)wr_id + 1; | |
164 | ||
165 | rdsdebug("ring %p ret %u wr_id %u oldest %u\n", ring, ret, | |
166 | wr_id, oldest); | |
167 | return ret; | |
168 | } |