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Source at commit 6c17a31f1fc515425221067cb3ece599c09dbc5d created 12 years 8 months ago. By Werner Almesberger, atusb, atben: moved from spi/ to ieee802154/; renamed atusb to spi_atusb | |
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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.com> |
9 | * |
10 | * This code tracks the priority of each CPU so that global migration |
11 | * decisions are easy to calculate. Each CPU can be in a state as follows: |
12 | * |
13 | * (INVALID), IDLE, NORMAL, RT1, ... RT99 |
14 | * |
15 | * going from the lowest priority to the highest. CPUs in the INVALID state |
16 | * are not eligible for routing. The system maintains this state with |
17 | * a 2 dimensional bitmap (the first for priority class, the second for cpus |
18 | * in that class). Therefore a typical application without affinity |
19 | * restrictions can find a suitable CPU with O(1) complexity (e.g. two bit |
20 | * searches). For tasks with affinity restrictions, the algorithm has a |
21 | * worst case complexity of O(min(102, nr_domcpus)), though the scenario that |
22 | * yields the worst case search is fairly contrived. |
23 | * |
24 | * This program is free software; you can redistribute it and/or |
25 | * modify it under the terms of the GNU General Public License |
26 | * as published by the Free Software Foundation; version 2 |
27 | * of the License. |
28 | */ |
29 | |
30 | #include <linux/gfp.h> |
31 | #include "sched_cpupri.h" |
32 | |
33 | /* Convert between a 140 based task->prio, and our 102 based cpupri */ |
34 | static int convert_prio(int prio) |
35 | { |
36 | int cpupri; |
37 | |
38 | if (prio == CPUPRI_INVALID) |
39 | cpupri = CPUPRI_INVALID; |
40 | else if (prio == MAX_PRIO) |
41 | cpupri = CPUPRI_IDLE; |
42 | else if (prio >= MAX_RT_PRIO) |
43 | cpupri = CPUPRI_NORMAL; |
44 | else |
45 | cpupri = MAX_RT_PRIO - prio + 1; |
46 | |
47 | return cpupri; |
48 | } |
49 | |
50 | #define for_each_cpupri_active(array, idx) \ |
51 | for_each_set_bit(idx, array, CPUPRI_NR_PRIORITIES) |
52 | |
53 | /** |
54 | * cpupri_find - find the best (lowest-pri) CPU in the system |
55 | * @cp: The cpupri context |
56 | * @p: The task |
57 | * @lowest_mask: A mask to fill in with selected CPUs (or NULL) |
58 | * |
59 | * Note: This function returns the recommended CPUs as calculated during the |
60 | * current invocation. By the time the call returns, the CPUs may have in |
61 | * fact changed priorities any number of times. While not ideal, it is not |
62 | * an issue of correctness since the normal rebalancer logic will correct |
63 | * any discrepancies created by racing against the uncertainty of the current |
64 | * priority configuration. |
65 | * |
66 | * Returns: (int)bool - CPUs were found |
67 | */ |
68 | int cpupri_find(struct cpupri *cp, struct task_struct *p, |
69 | struct cpumask *lowest_mask) |
70 | { |
71 | int idx = 0; |
72 | int task_pri = convert_prio(p->prio); |
73 | |
74 | for_each_cpupri_active(cp->pri_active, idx) { |
75 | struct cpupri_vec *vec = &cp->pri_to_cpu[idx]; |
76 | |
77 | if (idx >= task_pri) |
78 | break; |
79 | |
80 | if (cpumask_any_and(&p->cpus_allowed, vec->mask) >= nr_cpu_ids) |
81 | continue; |
82 | |
83 | if (lowest_mask) { |
84 | cpumask_and(lowest_mask, &p->cpus_allowed, vec->mask); |
85 | |
86 | /* |
87 | * We have to ensure that we have at least one bit |
88 | * still set in the array, since the map could have |
89 | * been concurrently emptied between the first and |
90 | * second reads of vec->mask. If we hit this |
91 | * condition, simply act as though we never hit this |
92 | * priority level and continue on. |
93 | */ |
94 | if (cpumask_any(lowest_mask) >= nr_cpu_ids) |
95 | continue; |
96 | } |
97 | |
98 | return 1; |
99 | } |
100 | |
101 | return 0; |
102 | } |
103 | |
104 | /** |
105 | * cpupri_set - update the cpu priority setting |
106 | * @cp: The cpupri context |
107 | * @cpu: The target cpu |
108 | * @pri: The priority (INVALID-RT99) to assign to this CPU |
109 | * |
110 | * Note: Assumes cpu_rq(cpu)->lock is locked |
111 | * |
112 | * Returns: (void) |
113 | */ |
114 | void cpupri_set(struct cpupri *cp, int cpu, int newpri) |
115 | { |
116 | int *currpri = &cp->cpu_to_pri[cpu]; |
117 | int oldpri = *currpri; |
118 | unsigned long flags; |
119 | |
120 | newpri = convert_prio(newpri); |
121 | |
122 | BUG_ON(newpri >= CPUPRI_NR_PRIORITIES); |
123 | |
124 | if (newpri == oldpri) |
125 | return; |
126 | |
127 | /* |
128 | * If the cpu was currently mapped to a different value, we |
129 | * need to map it to the new value then remove the old value. |
130 | * Note, we must add the new value first, otherwise we risk the |
131 | * cpu being cleared from pri_active, and this cpu could be |
132 | * missed for a push or pull. |
133 | */ |
134 | if (likely(newpri != CPUPRI_INVALID)) { |
135 | struct cpupri_vec *vec = &cp->pri_to_cpu[newpri]; |
136 | |
137 | raw_spin_lock_irqsave(&vec->lock, flags); |
138 | |
139 | cpumask_set_cpu(cpu, vec->mask); |
140 | vec->count++; |
141 | if (vec->count == 1) |
142 | set_bit(newpri, cp->pri_active); |
143 | |
144 | raw_spin_unlock_irqrestore(&vec->lock, flags); |
145 | } |
146 | if (likely(oldpri != CPUPRI_INVALID)) { |
147 | struct cpupri_vec *vec = &cp->pri_to_cpu[oldpri]; |
148 | |
149 | raw_spin_lock_irqsave(&vec->lock, flags); |
150 | |
151 | vec->count--; |
152 | if (!vec->count) |
153 | clear_bit(oldpri, cp->pri_active); |
154 | cpumask_clear_cpu(cpu, vec->mask); |
155 | |
156 | raw_spin_unlock_irqrestore(&vec->lock, flags); |
157 | } |
158 | |
159 | *currpri = newpri; |
160 | } |
161 | |
162 | /** |
163 | * cpupri_init - initialize the cpupri structure |
164 | * @cp: The cpupri context |
165 | * @bootmem: true if allocations need to use bootmem |
166 | * |
167 | * Returns: -ENOMEM if memory fails. |
168 | */ |
169 | int cpupri_init(struct cpupri *cp) |
170 | { |
171 | int i; |
172 | |
173 | memset(cp, 0, sizeof(*cp)); |
174 | |
175 | for (i = 0; i < CPUPRI_NR_PRIORITIES; i++) { |
176 | struct cpupri_vec *vec = &cp->pri_to_cpu[i]; |
177 | |
178 | raw_spin_lock_init(&vec->lock); |
179 | vec->count = 0; |
180 | if (!zalloc_cpumask_var(&vec->mask, GFP_KERNEL)) |
181 | goto cleanup; |
182 | } |
183 | |
184 | for_each_possible_cpu(i) |
185 | cp->cpu_to_pri[i] = CPUPRI_INVALID; |
186 | return 0; |
187 | |
188 | cleanup: |
189 | for (i--; i >= 0; i--) |
190 | free_cpumask_var(cp->pri_to_cpu[i].mask); |
191 | return -ENOMEM; |
192 | } |
193 | |
194 | /** |
195 | * cpupri_cleanup - clean up the cpupri structure |
196 | * @cp: The cpupri context |
197 | */ |
198 | void cpupri_cleanup(struct cpupri *cp) |
199 | { |
200 | int i; |
201 | |
202 | for (i = 0; i < CPUPRI_NR_PRIORITIES; i++) |
203 | free_cpumask_var(cp->pri_to_cpu[i].mask); |
204 | } |
205 |
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