xref: /titanic_50/usr/src/uts/common/io/nge/nge_atomic.c (revision 8b87c15576a5138f88a969448b43561bf5968c09)
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
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
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
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