Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | #include <linux/stop_machine.h> |
| 2 | #include <linux/kthread.h> |
| 3 | #include <linux/sched.h> |
| 4 | #include <linux/cpu.h> |
| 5 | #include <linux/err.h> |
| 6 | #include <linux/syscalls.h> |
| 7 | #include <asm/atomic.h> |
| 8 | #include <asm/semaphore.h> |
| 9 | #include <asm/uaccess.h> |
| 10 | |
| 11 | /* Since we effect priority and affinity (both of which are visible |
| 12 | * to, and settable by outside processes) we do indirection via a |
| 13 | * kthread. */ |
| 14 | |
| 15 | /* Thread to stop each CPU in user context. */ |
| 16 | enum stopmachine_state { |
| 17 | STOPMACHINE_WAIT, |
| 18 | STOPMACHINE_PREPARE, |
| 19 | STOPMACHINE_DISABLE_IRQ, |
| 20 | STOPMACHINE_EXIT, |
| 21 | }; |
| 22 | |
| 23 | static enum stopmachine_state stopmachine_state; |
| 24 | static unsigned int stopmachine_num_threads; |
| 25 | static atomic_t stopmachine_thread_ack; |
| 26 | static DECLARE_MUTEX(stopmachine_mutex); |
| 27 | |
Andrew Morton | d8cb7c1 | 2006-07-03 17:32:22 -0700 | [diff] [blame] | 28 | static int stopmachine(void *cpu) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 29 | { |
| 30 | int irqs_disabled = 0; |
| 31 | int prepared = 0; |
| 32 | |
Andrew Morton | d8cb7c1 | 2006-07-03 17:32:22 -0700 | [diff] [blame] | 33 | set_cpus_allowed(current, cpumask_of_cpu((int)(long)cpu)); |
| 34 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 35 | /* Ack: we are alive */ |
akpm@osdl.org | d59dd46 | 2005-05-01 08:58:47 -0700 | [diff] [blame] | 36 | smp_mb(); /* Theoretically the ack = 0 might not be on this CPU yet. */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 37 | atomic_inc(&stopmachine_thread_ack); |
| 38 | |
| 39 | /* Simple state machine */ |
| 40 | while (stopmachine_state != STOPMACHINE_EXIT) { |
| 41 | if (stopmachine_state == STOPMACHINE_DISABLE_IRQ |
| 42 | && !irqs_disabled) { |
| 43 | local_irq_disable(); |
| 44 | irqs_disabled = 1; |
| 45 | /* Ack: irqs disabled. */ |
akpm@osdl.org | d59dd46 | 2005-05-01 08:58:47 -0700 | [diff] [blame] | 46 | smp_mb(); /* Must read state first. */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 47 | atomic_inc(&stopmachine_thread_ack); |
| 48 | } else if (stopmachine_state == STOPMACHINE_PREPARE |
| 49 | && !prepared) { |
| 50 | /* Everyone is in place, hold CPU. */ |
| 51 | preempt_disable(); |
| 52 | prepared = 1; |
akpm@osdl.org | d59dd46 | 2005-05-01 08:58:47 -0700 | [diff] [blame] | 53 | smp_mb(); /* Must read state first. */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 54 | atomic_inc(&stopmachine_thread_ack); |
| 55 | } |
| 56 | /* Yield in first stage: migration threads need to |
| 57 | * help our sisters onto their CPUs. */ |
| 58 | if (!prepared && !irqs_disabled) |
| 59 | yield(); |
| 60 | else |
| 61 | cpu_relax(); |
| 62 | } |
| 63 | |
| 64 | /* Ack: we are exiting. */ |
akpm@osdl.org | d59dd46 | 2005-05-01 08:58:47 -0700 | [diff] [blame] | 65 | smp_mb(); /* Must read state first. */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 66 | atomic_inc(&stopmachine_thread_ack); |
| 67 | |
| 68 | if (irqs_disabled) |
| 69 | local_irq_enable(); |
| 70 | if (prepared) |
| 71 | preempt_enable(); |
| 72 | |
| 73 | return 0; |
| 74 | } |
| 75 | |
| 76 | /* Change the thread state */ |
| 77 | static void stopmachine_set_state(enum stopmachine_state state) |
| 78 | { |
| 79 | atomic_set(&stopmachine_thread_ack, 0); |
akpm@osdl.org | d59dd46 | 2005-05-01 08:58:47 -0700 | [diff] [blame] | 80 | smp_wmb(); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 81 | stopmachine_state = state; |
| 82 | while (atomic_read(&stopmachine_thread_ack) != stopmachine_num_threads) |
| 83 | cpu_relax(); |
| 84 | } |
| 85 | |
| 86 | static int stop_machine(void) |
| 87 | { |
Andrew Morton | d8cb7c1 | 2006-07-03 17:32:22 -0700 | [diff] [blame] | 88 | int i, ret = 0; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 89 | struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 }; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 90 | |
| 91 | /* One high-prio thread per cpu. We'll do this one. */ |
akpm@osdl.org | ed653a6 | 2006-01-09 20:51:38 -0800 | [diff] [blame] | 92 | sched_setscheduler(current, SCHED_FIFO, ¶m); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 93 | |
| 94 | atomic_set(&stopmachine_thread_ack, 0); |
| 95 | stopmachine_num_threads = 0; |
| 96 | stopmachine_state = STOPMACHINE_WAIT; |
| 97 | |
| 98 | for_each_online_cpu(i) { |
Ingo Molnar | 39c715b | 2005-06-21 17:14:34 -0700 | [diff] [blame] | 99 | if (i == raw_smp_processor_id()) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 100 | continue; |
Andrew Morton | d8cb7c1 | 2006-07-03 17:32:22 -0700 | [diff] [blame] | 101 | ret = kernel_thread(stopmachine, (void *)(long)i,CLONE_KERNEL); |
| 102 | if (ret < 0) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 103 | break; |
| 104 | stopmachine_num_threads++; |
| 105 | } |
| 106 | |
| 107 | /* Wait for them all to come to life. */ |
| 108 | while (atomic_read(&stopmachine_thread_ack) != stopmachine_num_threads) |
| 109 | yield(); |
| 110 | |
| 111 | /* If some failed, kill them all. */ |
| 112 | if (ret < 0) { |
| 113 | stopmachine_set_state(STOPMACHINE_EXIT); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 114 | return ret; |
| 115 | } |
| 116 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 117 | /* Now they are all started, make them hold the CPUs, ready. */ |
Kirill Korotaev | 4557398 | 2005-11-13 16:07:30 -0800 | [diff] [blame] | 118 | preempt_disable(); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 119 | stopmachine_set_state(STOPMACHINE_PREPARE); |
| 120 | |
| 121 | /* Make them disable irqs. */ |
Kirill Korotaev | 4557398 | 2005-11-13 16:07:30 -0800 | [diff] [blame] | 122 | local_irq_disable(); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 123 | stopmachine_set_state(STOPMACHINE_DISABLE_IRQ); |
| 124 | |
| 125 | return 0; |
| 126 | } |
| 127 | |
| 128 | static void restart_machine(void) |
| 129 | { |
| 130 | stopmachine_set_state(STOPMACHINE_EXIT); |
| 131 | local_irq_enable(); |
Kirill Korotaev | 4557398 | 2005-11-13 16:07:30 -0800 | [diff] [blame] | 132 | preempt_enable_no_resched(); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 133 | } |
| 134 | |
| 135 | struct stop_machine_data |
| 136 | { |
| 137 | int (*fn)(void *); |
| 138 | void *data; |
| 139 | struct completion done; |
| 140 | }; |
| 141 | |
| 142 | static int do_stop(void *_smdata) |
| 143 | { |
| 144 | struct stop_machine_data *smdata = _smdata; |
| 145 | int ret; |
| 146 | |
| 147 | ret = stop_machine(); |
| 148 | if (ret == 0) { |
| 149 | ret = smdata->fn(smdata->data); |
| 150 | restart_machine(); |
| 151 | } |
| 152 | |
| 153 | /* We're done: you can kthread_stop us now */ |
| 154 | complete(&smdata->done); |
| 155 | |
| 156 | /* Wait for kthread_stop */ |
| 157 | set_current_state(TASK_INTERRUPTIBLE); |
| 158 | while (!kthread_should_stop()) { |
| 159 | schedule(); |
| 160 | set_current_state(TASK_INTERRUPTIBLE); |
| 161 | } |
| 162 | __set_current_state(TASK_RUNNING); |
| 163 | return ret; |
| 164 | } |
| 165 | |
| 166 | struct task_struct *__stop_machine_run(int (*fn)(void *), void *data, |
| 167 | unsigned int cpu) |
| 168 | { |
| 169 | struct stop_machine_data smdata; |
| 170 | struct task_struct *p; |
| 171 | |
| 172 | smdata.fn = fn; |
| 173 | smdata.data = data; |
| 174 | init_completion(&smdata.done); |
| 175 | |
| 176 | down(&stopmachine_mutex); |
| 177 | |
| 178 | /* If they don't care which CPU fn runs on, bind to any online one. */ |
| 179 | if (cpu == NR_CPUS) |
Ingo Molnar | 39c715b | 2005-06-21 17:14:34 -0700 | [diff] [blame] | 180 | cpu = raw_smp_processor_id(); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 181 | |
| 182 | p = kthread_create(do_stop, &smdata, "kstopmachine"); |
| 183 | if (!IS_ERR(p)) { |
| 184 | kthread_bind(p, cpu); |
| 185 | wake_up_process(p); |
| 186 | wait_for_completion(&smdata.done); |
| 187 | } |
| 188 | up(&stopmachine_mutex); |
| 189 | return p; |
| 190 | } |
| 191 | |
| 192 | int stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu) |
| 193 | { |
| 194 | struct task_struct *p; |
| 195 | int ret; |
| 196 | |
| 197 | /* No CPUs can come up or down during this. */ |
| 198 | lock_cpu_hotplug(); |
| 199 | p = __stop_machine_run(fn, data, cpu); |
| 200 | if (!IS_ERR(p)) |
| 201 | ret = kthread_stop(p); |
| 202 | else |
| 203 | ret = PTR_ERR(p); |
| 204 | unlock_cpu_hotplug(); |
| 205 | |
| 206 | return ret; |
| 207 | } |