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 2007 Sun Microsystems, Inc. All rights reserved.
24 * Use is subject to license terms.
25 */
26
27 #pragma ident "%Z%%M% %I% %E% SMI"
28
29 #include "nge.h"
30
31 /*
32 * Atomically decrement a counter, but only if it will remain
33 * positive (>=0) afterwards.
34 */
35 boolean_t
nge_atomic_decrease(uint64_t * count_p,uint64_t n)36 nge_atomic_decrease(uint64_t *count_p, uint64_t n)
37 {
38 uint64_t oldval;
39 uint64_t newval;
40
41 /* ATOMICALLY */
42 do {
43 oldval = *count_p;
44 newval = oldval - n;
45 if (oldval < n)
46 return (B_FALSE);
47 } while (cas64(count_p, oldval, newval) != oldval);
48
49 return (B_TRUE);
50 }
51
52 /*
53 * Atomically increment a counter
54 */
55 void
nge_atomic_increase(uint64_t * count_p,uint64_t n)56 nge_atomic_increase(uint64_t *count_p, uint64_t n)
57 {
58 uint64_t oldval;
59 uint64_t newval;
60
61 /* ATOMICALLY */
62 do {
63 oldval = *count_p;
64 newval = oldval + n;
65 } while (cas64(count_p, oldval, newval) != oldval);
66 }
67
68
69 /*
70 * Atomically shift a 32-bit word left, returning
71 * the value it had *before* the shift was applied
72 */
73 uint32_t
nge_atomic_shl32(uint32_t * sp,uint_t count)74 nge_atomic_shl32(uint32_t *sp, uint_t count)
75 {
76 uint32_t oldval;
77 uint32_t newval;
78
79 /* ATOMICALLY */
80 do {
81 oldval = *sp;
82 newval = oldval << count;
83 } while (cas32(sp, oldval, newval) != oldval);
84
85 return (oldval);
86 }
87