kernel-ark/kernel/stop_machine.c
Mike Travis 65c0118453 cpumask: Replace cpumask_of_cpu with cpumask_of_cpu_ptr
* This patch replaces the dangerous lvalue version of cpumask_of_cpu
    with new cpumask_of_cpu_ptr macros.  These are patterned after the
    node_to_cpumask_ptr macros.

    In general terms, if there is a cpumask_of_cpu_map[] then a pointer to
    the cpumask_of_cpu_map[cpu] entry is used.  The cpumask_of_cpu_map
    is provided when there is a large NR_CPUS count, reducing
    greatly the amount of code generated and stack space used for
    cpumask_of_cpu().  The pointer to the cpumask_t value is needed for
    calling set_cpus_allowed_ptr() to reduce the amount of stack space
    needed to pass the cpumask_t value.

    If there isn't a cpumask_of_cpu_map[], then a temporary variable is
    declared and filled in with value from cpumask_of_cpu(cpu) as well as
    a pointer variable pointing to this temporary variable.  Afterwards,
    the pointer is used to reference the cpumask value.  The compiler
    will optimize out the extra dereference through the pointer as well
    as the stack space used for the pointer, resulting in identical code.

    A good example of the orthogonal usages is in net/sunrpc/svc.c:

	case SVC_POOL_PERCPU:
	{
		unsigned int cpu = m->pool_to[pidx];
		cpumask_of_cpu_ptr(cpumask, cpu);

		*oldmask = current->cpus_allowed;
		set_cpus_allowed_ptr(current, cpumask);
		return 1;
	}
	case SVC_POOL_PERNODE:
	{
		unsigned int node = m->pool_to[pidx];
		node_to_cpumask_ptr(nodecpumask, node);

		*oldmask = current->cpus_allowed;
		set_cpus_allowed_ptr(current, nodecpumask);
		return 1;
	}

Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-18 22:02:57 +02:00

217 lines
5.0 KiB
C

/* 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;
cpumask_of_cpu_ptr(cpumask, (int)(long)cpu);
set_cpus_allowed_ptr(current, cpumask);
/* 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();
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();
cpu_relax();
}
/* 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_nocheck(p, SCHED_FIFO, &param);
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);