xref: /illumos-gate/usr/src/uts/common/os/cpu_intr.c (revision 7c478bd9)
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, Version 1.0 only
6  * (the "License").  You may not use this file except in compliance
7  * with the License.
8  *
9  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
10  * or http://www.opensolaris.org/os/licensing.
11  * See the License for the specific language governing permissions
12  * and limitations under the License.
13  *
14  * When distributing Covered Code, include this CDDL HEADER in each
15  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
16  * If applicable, add the following below this CDDL HEADER, with the
17  * fields enclosed by brackets "[]" replaced with your own identifying
18  * information: Portions Copyright [yyyy] [name of copyright owner]
19  *
20  * CDDL HEADER END
21  */
22 /*
23  * Copyright 2005 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 <sys/types.h>
30 #include <sys/param.h>
31 #include <sys/var.h>
32 #include <sys/thread.h>
33 #include <sys/cpuvar.h>
34 #include <sys/kstat.h>
35 #include <sys/uadmin.h>
36 #include <sys/systm.h>
37 #include <sys/errno.h>
38 #include <sys/cmn_err.h>
39 #include <sys/procset.h>
40 #include <sys/processor.h>
41 #include <sys/debug.h>
42 #include <sys/cyclic.h>
43 #include <sys/pool_pset.h>
44 
45 /*
46  * cpu_intr_on - determine whether the CPU is participating
47  * in I/O interrupts.
48  */
49 int
cpu_intr_on(cpu_t * cp)50 cpu_intr_on(cpu_t *cp)
51 {
52 	ASSERT(MUTEX_HELD(&cpu_lock));
53 	return ((cp->cpu_flags & CPU_ENABLE) != 0);
54 }
55 
56 /*
57  * Return the next on-line CPU handling interrupts.
58  */
59 cpu_t *
cpu_intr_next(cpu_t * cp)60 cpu_intr_next(cpu_t *cp)
61 {
62 	cpu_t	*c;
63 
64 	ASSERT(MUTEX_HELD(&cpu_lock));
65 
66 	c = cp->cpu_next_onln;
67 	while (c != cp) {
68 		if (cpu_intr_on(c)) {
69 			return (c);
70 		}
71 		c = c->cpu_next_onln;
72 	}
73 	return (NULL);
74 }
75 
76 /*
77  * cpu_intr_count - count how many CPUs are handling I/O interrupts.
78  */
79 int
cpu_intr_count(cpu_t * cp)80 cpu_intr_count(cpu_t *cp)
81 {
82 	cpu_t	*c;
83 	int	count = 0;
84 
85 	ASSERT(MUTEX_HELD(&cpu_lock));
86 	c = cp;
87 	do {
88 		if (cpu_intr_on(c)) {
89 			++count;
90 		}
91 	} while ((c = c->cpu_next) != cp);
92 	return (count);
93 }
94 
95 /*
96  * Enable I/O interrupts on this CPU, if they are disabled.
97  */
98 void
cpu_intr_enable(cpu_t * cp)99 cpu_intr_enable(cpu_t *cp)
100 {
101 	ASSERT(MUTEX_HELD(&cpu_lock));
102 	if (!cpu_intr_on(cp)) {
103 		cpu_enable_intr(cp);
104 		cpu_set_state(cp);
105 	}
106 }
107 
108 /*
109  * cpu_intr_disable - redirect I/O interrupts targetted at this CPU.
110  *
111  * semantics: We check the count of CPUs that are accepting
112  * interrupts, because it's stupid to take the last CPU out
113  * of I/O interrupt participation. This also permits the
114  * p_online syscall to fail gracefully in uniprocessor configurations
115  * without having to perform any special platform-specific operations.
116  */
117 int
cpu_intr_disable(cpu_t * cp)118 cpu_intr_disable(cpu_t *cp)
119 {
120 	int	e = EBUSY;
121 
122 	ASSERT(MUTEX_HELD(&cpu_lock));
123 	if ((cpu_intr_count(cp) > 1) && (cpu_intr_next(cp) != NULL)) {
124 		if (cpu_intr_on(cp)) {
125 			/*
126 			 * Juggle away cyclics, but don't fail if we don't
127 			 * manage to juggle all of them away; we want to allow
128 			 * CPU-bound cyclics to continue to fire on the
129 			 * sheltered CPU.
130 			 */
131 			(void) cyclic_juggle(cp);
132 			e = cpu_disable_intr(cp);
133 		}
134 	}
135 	if (e == 0)
136 		cpu_set_state(cp);
137 	return (e);
138 }
139