mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-27 19:29:37 +00:00
![Rusty Russell](/assets/img/avatar_default.png)
I had to look back: this code was extracted from the module.c code in 2005. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
210 lines
4.8 KiB
C
210 lines
4.8 KiB
C
/* Copyright 2005 Rusty Russell rusty@rustcorp.com.au IBM Corporation.
|
|
* GPL v2 and any later version.
|
|
*/
|
|
#include <linux/stop_machine.h>
|
|
#include <linux/kthread.h>
|
|
#include <linux/sched.h>
|
|
#include <linux/cpu.h>
|
|
#include <linux/err.h>
|
|
#include <linux/syscalls.h>
|
|
#include <asm/atomic.h>
|
|
#include <asm/semaphore.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 DECLARE_MUTEX(stopmachine_mutex);
|
|
|
|
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();
|
|
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;
|
|
struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
|
|
|
|
/* One high-prio thread per cpu. We'll do this one. */
|
|
sched_setscheduler(current, SCHED_FIFO, ¶m);
|
|
|
|
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();
|
|
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)
|
|
{
|
|
struct stop_machine_data smdata;
|
|
struct task_struct *p;
|
|
|
|
smdata.fn = fn;
|
|
smdata.data = data;
|
|
init_completion(&smdata.done);
|
|
|
|
down(&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)) {
|
|
kthread_bind(p, cpu);
|
|
wake_up_process(p);
|
|
wait_for_completion(&smdata.done);
|
|
}
|
|
up(&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. */
|
|
lock_cpu_hotplug();
|
|
p = __stop_machine_run(fn, data, cpu);
|
|
if (!IS_ERR(p))
|
|
ret = kthread_stop(p);
|
|
else
|
|
ret = PTR_ERR(p);
|
|
unlock_cpu_hotplug();
|
|
|
|
return ret;
|
|
}
|