projects/linux·blob v2.6.22-rc4 · refs

216 lines · 4.9 KiB

1/* Copyright 2005 Rusty Russell [email protected] IBM Corporation.
2 * GPL v2 and any later version.
3 */
4#include <linux/cpu.h>
5#include <linux/err.h>
6#include <linux/kthread.h>
7#include <linux/module.h>
8#include <linux/sched.h>
9#include <linux/stop_machine.h>
10#include <linux/syscalls.h>
11#include <linux/interrupt.h>
12
13#include <asm/atomic.h>
14#include <asm/semaphore.h>
15#include <asm/uaccess.h>
16
17/* Since we effect priority and affinity (both of which are visible
18 * to, and settable by outside processes) we do indirection via a
19 * kthread. */
20
21/* Thread to stop each CPU in user context. */
22enum stopmachine_state {
23 STOPMACHINE_WAIT,
24 STOPMACHINE_PREPARE,
25 STOPMACHINE_DISABLE_IRQ,
26 STOPMACHINE_EXIT,
27};
28
29static enum stopmachine_state stopmachine_state;
30static unsigned int stopmachine_num_threads;
31static atomic_t stopmachine_thread_ack;
32static DECLARE_MUTEX(stopmachine_mutex);
33
34static int stopmachine(void *cpu)
35{
36 int irqs_disabled = 0;
37 int prepared = 0;
38
39 set_cpus_allowed(current, cpumask_of_cpu((int)(long)cpu));
40
41 /* Ack: we are alive */
42 smp_mb(); /* Theoretically the ack = 0 might not be on this CPU yet. */
43 atomic_inc(&stopmachine_thread_ack);
44
45 /* Simple state machine */
46 while (stopmachine_state != STOPMACHINE_EXIT) {
47 if (stopmachine_state == STOPMACHINE_DISABLE_IRQ
48 && !irqs_disabled) {
49 local_irq_disable();
50 hard_irq_disable();
51 irqs_disabled = 1;
52 /* Ack: irqs disabled. */
53 smp_mb(); /* Must read state first. */
54 atomic_inc(&stopmachine_thread_ack);
55 } else if (stopmachine_state == STOPMACHINE_PREPARE
56 && !prepared) {
57 /* Everyone is in place, hold CPU. */
58 preempt_disable();
59 prepared = 1;
60 smp_mb(); /* Must read state first. */
61 atomic_inc(&stopmachine_thread_ack);
62 }
63 /* Yield in first stage: migration threads need to
64 * help our sisters onto their CPUs. */
65 if (!prepared && !irqs_disabled)
66 yield();
67 else
68 cpu_relax();
69 }
70
71 /* Ack: we are exiting. */
72 smp_mb(); /* Must read state first. */
73 atomic_inc(&stopmachine_thread_ack);
74
75 if (irqs_disabled)
76 local_irq_enable();
77 if (prepared)
78 preempt_enable();
79
80 return 0;
81}
82
83/* Change the thread state */
84static void stopmachine_set_state(enum stopmachine_state state)
85{
86 atomic_set(&stopmachine_thread_ack, 0);
87 smp_wmb();
88 stopmachine_state = state;
89 while (atomic_read(&stopmachine_thread_ack) != stopmachine_num_threads)
90 cpu_relax();
91}
92
93static int stop_machine(void)
94{
95 int i, ret = 0;
96 struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
97
98 /* One high-prio thread per cpu. We'll do this one. */
99 sched_setscheduler(current, SCHED_FIFO, &param);
100
101 atomic_set(&stopmachine_thread_ack, 0);
102 stopmachine_num_threads = 0;
103 stopmachine_state = STOPMACHINE_WAIT;
104
105 for_each_online_cpu(i) {
106 if (i == raw_smp_processor_id())
107 continue;
108 ret = kernel_thread(stopmachine, (void *)(long)i,CLONE_KERNEL);
109 if (ret < 0)
110 break;
111 stopmachine_num_threads++;
112 }
113
114 /* Wait for them all to come to life. */
115 while (atomic_read(&stopmachine_thread_ack) != stopmachine_num_threads)
116 yield();
117
118 /* If some failed, kill them all. */
119 if (ret < 0) {
120 stopmachine_set_state(STOPMACHINE_EXIT);
121 return ret;
122 }
123
124 /* Now they are all started, make them hold the CPUs, ready. */
125 preempt_disable();
126 stopmachine_set_state(STOPMACHINE_PREPARE);
127
128 /* Make them disable irqs. */
129 local_irq_disable();
130 hard_irq_disable();
131 stopmachine_set_state(STOPMACHINE_DISABLE_IRQ);
132
133 return 0;
134}
135
136static void restart_machine(void)
137{
138 stopmachine_set_state(STOPMACHINE_EXIT);
139 local_irq_enable();
140 preempt_enable_no_resched();
141}
142
143struct stop_machine_data
144{
145 int (*fn)(void *);
146 void *data;
147 struct completion done;
148};
149
150static int do_stop(void *_smdata)
151{
152 struct stop_machine_data *smdata = _smdata;
153 int ret;
154
155 ret = stop_machine();
156 if (ret == 0) {
157 ret = smdata->fn(smdata->data);
158 restart_machine();
159 }
160
161 /* We're done: you can kthread_stop us now */
162 complete(&smdata->done);
163
164 /* Wait for kthread_stop */
165 set_current_state(TASK_INTERRUPTIBLE);
166 while (!kthread_should_stop()) {
167 schedule();
168 set_current_state(TASK_INTERRUPTIBLE);
169 }
170 __set_current_state(TASK_RUNNING);
171 return ret;
172}
173
174struct task_struct *__stop_machine_run(int (*fn)(void *), void *data,
175 unsigned int cpu)
176{
177 struct stop_machine_data smdata;
178 struct task_struct *p;
179
180 smdata.fn = fn;
181 smdata.data = data;
182 init_completion(&smdata.done);
183
184 down(&stopmachine_mutex);
185
186 /* If they don't care which CPU fn runs on, bind to any online one. */
187 if (cpu == NR_CPUS)
188 cpu = raw_smp_processor_id();
189
190 p = kthread_create(do_stop, &smdata, "kstopmachine");
191 if (!IS_ERR(p)) {
192 kthread_bind(p, cpu);
193 wake_up_process(p);
194 wait_for_completion(&smdata.done);
195 }
196 up(&stopmachine_mutex);
197 return p;
198}
199
200int stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu)
201{
202 struct task_struct *p;
203 int ret;
204
205 /* No CPUs can come up or down during this. */
206 lock_cpu_hotplug();
207 p = __stop_machine_run(fn, data, cpu);
208 if (!IS_ERR(p))
209 ret = kthread_stop(p);
210 else
211 ret = PTR_ERR(p);
212 unlock_cpu_hotplug();
213
214 return ret;
215}
216EXPORT_SYMBOL_GPL(stop_machine_run);