1 /*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21
22 /*
23 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
24 * Use is subject to license terms.
25 */
26
27 #include "bge_impl.h"
28
29 /*
30 * Atomically decrement a counter, but only if it will remain
31 * strictly positive (greater than zero) afterwards. We return
32 * the decremented value if so, otherwise zero (in which case
33 * the counter is unchanged).
34 *
35 * This is used for keeping track of available resources such
36 * as transmit ring slots ...
37 */
38 uint64_t
bge_atomic_reserve(uint64_t * count_p,uint64_t n)39 bge_atomic_reserve(uint64_t *count_p, uint64_t n)
40 {
41 uint64_t oldval;
42 uint64_t newval;
43
44 /* ATOMICALLY */
45 do {
46 oldval = *count_p;
47 newval = oldval - n;
48 if (oldval <= n)
49 return (0); /* no resources left */
50 } while (atomic_cas_64(count_p, oldval, newval) != oldval);
51
52 return (newval);
53 }
54
55 /*
56 * Atomically increment a counter
57 */
58 void
bge_atomic_renounce(uint64_t * count_p,uint64_t n)59 bge_atomic_renounce(uint64_t *count_p, uint64_t n)
60 {
61 uint64_t oldval;
62 uint64_t newval;
63
64 /* ATOMICALLY */
65 do {
66 oldval = *count_p;
67 newval = oldval + n;
68 } while (atomic_cas_64(count_p, oldval, newval) != oldval);
69 }
70
71 /*
72 * Atomically claim a slot in a descriptor ring
73 */
74 uint64_t
bge_atomic_claim(uint64_t * count_p,uint64_t limit)75 bge_atomic_claim(uint64_t *count_p, uint64_t limit)
76 {
77 uint64_t oldval;
78 uint64_t newval;
79
80 /* ATOMICALLY */
81 do {
82 oldval = *count_p;
83 newval = NEXT(oldval, limit);
84 } while (atomic_cas_64(count_p, oldval, newval) != oldval);
85
86 return (oldval);
87 }
88
89 /*
90 * Atomically NEXT a 64-bit integer, returning the
91 * value it had *before* the NEXT was applied
92 */
93 uint64_t
bge_atomic_next(uint64_t * sp,uint64_t limit)94 bge_atomic_next(uint64_t *sp, uint64_t limit)
95 {
96 uint64_t oldval;
97 uint64_t newval;
98
99 /* ATOMICALLY */
100 do {
101 oldval = *sp;
102 newval = NEXT(oldval, limit);
103 } while (atomic_cas_64(sp, oldval, newval) != oldval);
104
105 return (oldval);
106 }
107
108 /*
109 * Atomically decrement a counter
110 */
111 void
bge_atomic_sub64(uint64_t * count_p,uint64_t n)112 bge_atomic_sub64(uint64_t *count_p, uint64_t n)
113 {
114 uint64_t oldval;
115 uint64_t newval;
116
117 /* ATOMICALLY */
118 do {
119 oldval = *count_p;
120 newval = oldval - n;
121 } while (atomic_cas_64(count_p, oldval, newval) != oldval);
122 }
123
124 /*
125 * Atomically clear bits in a 64-bit word, returning
126 * the value it had *before* the bits were cleared.
127 */
128 uint64_t
bge_atomic_clr64(uint64_t * sp,uint64_t bits)129 bge_atomic_clr64(uint64_t *sp, uint64_t bits)
130 {
131 uint64_t oldval;
132 uint64_t newval;
133
134 /* ATOMICALLY */
135 do {
136 oldval = *sp;
137 newval = oldval & ~bits;
138 } while (atomic_cas_64(sp, oldval, newval) != oldval);
139
140 return (oldval);
141 }
142
143 /*
144 * Atomically shift a 32-bit word left, returning
145 * the value it had *before* the shift was applied
146 */
147 uint32_t
bge_atomic_shl32(uint32_t * sp,uint_t count)148 bge_atomic_shl32(uint32_t *sp, uint_t count)
149 {
150 uint32_t oldval;
151 uint32_t newval;
152
153 /* ATOMICALLY */
154 do {
155 oldval = *sp;
156 newval = oldval << count;
157 } while (atomic_cas_32(sp, oldval, newval) != oldval);
158
159 return (oldval);
160 }
161