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1 /* 1
2 * kernel/sched_cpupri.c
3 *
4 * CPU priority management
5 *
6 * Copyright (C) 2007-2008 Novell
7 *
8 * Author: Gregory Haskins <ghaskins@novell.c
9 *
10 * This code tracks the priority of each CPU
11 * decisions are easy to calculate. Each CPU
12 *
13 * (INVALID), IDLE, NORMAL, RT
14 *
15 * going from the lowest priority to the high
16 * are not eligible for routing. The system
17 * a 2 dimensional bitmap (the first for prio
18 * in that class). Therefore a typical appli
19 * restrictions can find a suitable CPU with
20 * searches). For tasks with affinity restri
21 * worst case complexity of O(min(102, nr_dom
22 * yields the worst case search is fairly con
23 *
24 * This program is free software; you can red
25 * modify it under the terms of the GNU Gener
26 * as published by the Free Software Foundati
27 * of the License.
28 */
29
30 #include "sched_cpupri.h"
31
32 /* Convert between a 140 based task->prio, and
33 static int convert_prio(int prio)
34 {
35 int cpupri;
36
37 if (prio == CPUPRI_INVALID)
38 cpupri = CPUPRI_INVALID;
39 else if (prio == MAX_PRIO)
40 cpupri = CPUPRI_IDLE;
41 else if (prio >= MAX_RT_PRIO)
42 cpupri = CPUPRI_NORMAL;
43 else
44 cpupri = MAX_RT_PRIO - prio +
45
46 return cpupri;
47 }
48
49 #define for_each_cpupri_active(array, idx)
50 for (idx = find_first_bit(array, CPUPRI_NR_P
51 idx < CPUPRI_NR_PRIORITIES;
52 idx = find_next_bit(array, CPUPRI_NR_PR
53
54 /**
55 * cpupri_find - find the best (lowest-pri) CP
56 * @cp: The cpupri context
57 * @p: The task
58 * @lowest_mask: A mask to fill in with select
59 *
60 * Note: This function returns the recommended
61 * current invokation. By the time the call r
62 * fact changed priorities any number of times
63 * an issue of correctness since the normal re
64 * any discrepancies created by racing against
65 * priority configuration.
66 *
67 * Returns: (int)bool - CPUs were found
68 */
69 int cpupri_find(struct cpupri *cp, struct task
70 struct cpumask *lowest_mask)
71 {
72 int idx = 0;
73 int task_pri = conver
74
75 for_each_cpupri_active(cp->pri_active,
76 struct cpupri_vec *vec = &cp-
77
78 if (idx >= task_pri)
79 break;
80
81 if (cpumask_any_and(&p->cpus_a
82 continue;
83
84 if (lowest_mask) {
85 cpumask_and(lowest_mas
86
87 /*
88 * We have to ensure t
89 * still set in the ar
90 * been concurrently e
91 * second reads of vec
92 * condition, simply a
93 * priority level and
94 */
95 if (cpumask_any(lowest
96 continue;
97 }
98
99 return 1;
100 }
101
102 return 0;
103 }
104
105 /**
106 * cpupri_set - update the cpu priority settin
107 * @cp: The cpupri context
108 * @cpu: The target cpu
109 * @pri: The priority (INVALID-RT99) to assign
110 *
111 * Note: Assumes cpu_rq(cpu)->lock is locked
112 *
113 * Returns: (void)
114 */
115 void cpupri_set(struct cpupri *cp, int cpu, in
116 {
117 int *currpri = &cp->cp
118 int oldpri = *currpr
119 unsigned long flags;
120
121 newpri = convert_prio(newpri);
122
123 BUG_ON(newpri >= CPUPRI_NR_PRIORITIES)
124
125 if (newpri == oldpri)
126 return;
127
128 /*
129 * If the cpu was currently mapped to
130 * first need to unmap the old value
131 */
132 if (likely(oldpri != CPUPRI_INVALID))
133 struct cpupri_vec *vec = &cp-
134
135 spin_lock_irqsave(&vec->lock,
136
137 vec->count--;
138 if (!vec->count)
139 clear_bit(oldpri, cp->
140 cpumask_clear_cpu(cpu, vec->ma
141
142 spin_unlock_irqrestore(&vec->l
143 }
144
145 if (likely(newpri != CPUPRI_INVALID))
146 struct cpupri_vec *vec = &cp->
147
148 spin_lock_irqsave(&vec->lock,
149
150 cpumask_set_cpu(cpu, vec->mask
151 vec->count++;
152 if (vec->count == 1)
153 set_bit(newpri, cp->pr
154
155 spin_unlock_irqrestore(&vec->l
156 }
157
158 *currpri = newpri;
159 }
160
161 /**
162 * cpupri_init - initialize the cpupri structu
163 * @cp: The cpupri context
164 * @bootmem: true if allocations need to use b
165 *
166 * Returns: -ENOMEM if memory fails.
167 */
168 int cpupri_init(struct cpupri *cp, bool bootme
169 {
170 gfp_t gfp = GFP_KERNEL;
171 int i;
172
173 if (bootmem)
174 gfp = GFP_NOWAIT;
175
176 memset(cp, 0, sizeof(*cp));
177
178 for (i = 0; i < CPUPRI_NR_PRIORITIES;
179 struct cpupri_vec *vec = &cp->
180
181 spin_lock_init(&vec->lock);
182 vec->count = 0;
183 if (!zalloc_cpumask_var(&vec->
184 goto cleanup;
185 }
186
187 for_each_possible_cpu(i)
188 cp->cpu_to_pri[i] = CPUPRI_INV
189 return 0;
190
191 cleanup:
192 for (i--; i >= 0; i--)
193 free_cpumask_var(cp->pri_to_cp
194 return -ENOMEM;
195 }
196
197 /**
198 * cpupri_cleanup - clean up the cpupri struct
199 * @cp: The cpupri context
200 */
201 void cpupri_cleanup(struct cpupri *cp)
202 {
203 int i;
204
205 for (i = 0; i < CPUPRI_NR_PRIORITIES;
206 free_cpumask_var(cp->pri_to_cp
207 }
208
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