xref: /titanic_51/usr/src/uts/common/io/nge/nge_atomic.c (revision b3697b90e692e3e5d859fb77d285d4c056d99eda)
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
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
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
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