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