blob: 319821ef78afc9e0a7488cbf9b2ea1c5853b65c1 [file] [log] [blame]
Rusty Russelle5582ca2006-09-29 02:01:35 -07001/* Copyright 2005 Rusty Russell rusty@rustcorp.com.au IBM Corporation.
2 * GPL v2 and any later version.
3 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07004#include <linux/cpu.h>
5#include <linux/err.h>
Prarit Bhargavaee527cd2007-05-08 00:25:08 -07006#include <linux/kthread.h>
7#include <linux/module.h>
8#include <linux/sched.h>
9#include <linux/stop_machine.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070010#include <linux/syscalls.h>
Benjamin Herrenschmidta12bb442007-05-10 22:22:47 -070011#include <linux/interrupt.h>
12
Linus Torvalds1da177e2005-04-16 15:20:36 -070013#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
Andrew Mortond8cb7c12006-07-03 17:32:22 -070034static int stopmachine(void *cpu)
Linus Torvalds1da177e2005-04-16 15:20:36 -070035{
36 int irqs_disabled = 0;
37 int prepared = 0;
38
Andrew Mortond8cb7c12006-07-03 17:32:22 -070039 set_cpus_allowed(current, cpumask_of_cpu((int)(long)cpu));
40
Linus Torvalds1da177e2005-04-16 15:20:36 -070041 /* Ack: we are alive */
akpm@osdl.orgd59dd462005-05-01 08:58:47 -070042 smp_mb(); /* Theoretically the ack = 0 might not be on this CPU yet. */
Linus Torvalds1da177e2005-04-16 15:20:36 -070043 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();
Benjamin Herrenschmidta12bb442007-05-10 22:22:47 -070050 hard_irq_disable();
Linus Torvalds1da177e2005-04-16 15:20:36 -070051 irqs_disabled = 1;
52 /* Ack: irqs disabled. */
akpm@osdl.orgd59dd462005-05-01 08:58:47 -070053 smp_mb(); /* Must read state first. */
Linus Torvalds1da177e2005-04-16 15:20:36 -070054 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;
akpm@osdl.orgd59dd462005-05-01 08:58:47 -070060 smp_mb(); /* Must read state first. */
Linus Torvalds1da177e2005-04-16 15:20:36 -070061 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. */
akpm@osdl.orgd59dd462005-05-01 08:58:47 -070072 smp_mb(); /* Must read state first. */
Linus Torvalds1da177e2005-04-16 15:20:36 -070073 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);
akpm@osdl.orgd59dd462005-05-01 08:58:47 -070087 smp_wmb();
Linus Torvalds1da177e2005-04-16 15:20:36 -070088 stopmachine_state = state;
89 while (atomic_read(&stopmachine_thread_ack) != stopmachine_num_threads)
90 cpu_relax();
91}
92
93static int stop_machine(void)
94{
Andrew Mortond8cb7c12006-07-03 17:32:22 -070095 int i, ret = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -070096
97 atomic_set(&stopmachine_thread_ack, 0);
98 stopmachine_num_threads = 0;
99 stopmachine_state = STOPMACHINE_WAIT;
100
101 for_each_online_cpu(i) {
Ingo Molnar39c715b2005-06-21 17:14:34 -0700102 if (i == raw_smp_processor_id())
Linus Torvalds1da177e2005-04-16 15:20:36 -0700103 continue;
Andrew Mortond8cb7c12006-07-03 17:32:22 -0700104 ret = kernel_thread(stopmachine, (void *)(long)i,CLONE_KERNEL);
105 if (ret < 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700106 break;
107 stopmachine_num_threads++;
108 }
109
110 /* Wait for them all to come to life. */
111 while (atomic_read(&stopmachine_thread_ack) != stopmachine_num_threads)
112 yield();
113
114 /* If some failed, kill them all. */
115 if (ret < 0) {
116 stopmachine_set_state(STOPMACHINE_EXIT);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700117 return ret;
118 }
119
Linus Torvalds1da177e2005-04-16 15:20:36 -0700120 /* Now they are all started, make them hold the CPUs, ready. */
Kirill Korotaev45573982005-11-13 16:07:30 -0800121 preempt_disable();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700122 stopmachine_set_state(STOPMACHINE_PREPARE);
123
124 /* Make them disable irqs. */
Kirill Korotaev45573982005-11-13 16:07:30 -0800125 local_irq_disable();
Benjamin Herrenschmidta12bb442007-05-10 22:22:47 -0700126 hard_irq_disable();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700127 stopmachine_set_state(STOPMACHINE_DISABLE_IRQ);
128
129 return 0;
130}
131
132static void restart_machine(void)
133{
134 stopmachine_set_state(STOPMACHINE_EXIT);
135 local_irq_enable();
Kirill Korotaev45573982005-11-13 16:07:30 -0800136 preempt_enable_no_resched();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700137}
138
139struct stop_machine_data
140{
141 int (*fn)(void *);
142 void *data;
143 struct completion done;
144};
145
146static int do_stop(void *_smdata)
147{
148 struct stop_machine_data *smdata = _smdata;
149 int ret;
150
151 ret = stop_machine();
152 if (ret == 0) {
153 ret = smdata->fn(smdata->data);
154 restart_machine();
155 }
156
157 /* We're done: you can kthread_stop us now */
158 complete(&smdata->done);
159
160 /* Wait for kthread_stop */
161 set_current_state(TASK_INTERRUPTIBLE);
162 while (!kthread_should_stop()) {
163 schedule();
164 set_current_state(TASK_INTERRUPTIBLE);
165 }
166 __set_current_state(TASK_RUNNING);
167 return ret;
168}
169
170struct task_struct *__stop_machine_run(int (*fn)(void *), void *data,
171 unsigned int cpu)
172{
173 struct stop_machine_data smdata;
174 struct task_struct *p;
175
176 smdata.fn = fn;
177 smdata.data = data;
178 init_completion(&smdata.done);
179
180 down(&stopmachine_mutex);
181
182 /* If they don't care which CPU fn runs on, bind to any online one. */
183 if (cpu == NR_CPUS)
Ingo Molnar39c715b2005-06-21 17:14:34 -0700184 cpu = raw_smp_processor_id();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700185
186 p = kthread_create(do_stop, &smdata, "kstopmachine");
187 if (!IS_ERR(p)) {
Satoru Takeuchi85653af2007-07-15 23:39:47 -0700188 struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
189
190 /* One high-prio thread per cpu. We'll do this one. */
191 sched_setscheduler(p, SCHED_FIFO, &param);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700192 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}
Prarit Bhargavaee527cd2007-05-08 00:25:08 -0700216EXPORT_SYMBOL_GPL(stop_machine_run);