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 #include "nge.h"
28
29 /*
30 * Atomically decrement a counter, but only if it will remain
31 * positive (>=0) afterwards.
32 */
33 boolean_t
nge_atomic_decrease(uint64_t * count_p,uint64_t n)34 nge_atomic_decrease(uint64_t *count_p, uint64_t n)
35 {
36 uint64_t oldval;
37 uint64_t newval;
38
39 /* ATOMICALLY */
40 do {
41 oldval = *count_p;
42 newval = oldval - n;
43 if (oldval < n)
44 return (B_FALSE);
45 } while (atomic_cas_64(count_p, oldval, newval) != oldval);
46
47 return (B_TRUE);
48 }
49
50 /*
51 * Atomically increment a counter
52 */
53 void
nge_atomic_increase(uint64_t * count_p,uint64_t n)54 nge_atomic_increase(uint64_t *count_p, uint64_t n)
55 {
56 uint64_t oldval;
57 uint64_t newval;
58
59 /* ATOMICALLY */
60 do {
61 oldval = *count_p;
62 newval = oldval + n;
63 } while (atomic_cas_64(count_p, oldval, newval) != oldval);
64 }
65
66
67 /*
68 * Atomically shift a 32-bit word left, returning
69 * the value it had *before* the shift was applied
70 */
71 uint32_t
nge_atomic_shl32(uint32_t * sp,uint_t count)72 nge_atomic_shl32(uint32_t *sp, uint_t count)
73 {
74 uint32_t oldval;
75 uint32_t newval;
76
77 /* ATOMICALLY */
78 do {
79 oldval = *sp;
80 newval = oldval << count;
81 } while (atomic_cas_32(sp, oldval, newval) != oldval);
82
83 return (oldval);
84 }
85