forked from luck/tmp_suning_uos_patched
Simplify stop_machine
stop_machine creates a kthread which creates kernel threads. We can create those threads directly and simplify things a little. Some care must be taken with CPU hotunplug, which has special needs, but that code seems more robust than it was in the past. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
This commit is contained in:
parent
5c2aed6225
commit
ffdb5976c4
|
@ -17,13 +17,12 @@
|
|||
* @data: the data ptr for the @fn()
|
||||
* @cpu: if @cpu == n, run @fn() on cpu n
|
||||
* if @cpu == NR_CPUS, run @fn() on any cpu
|
||||
* if @cpu == ALL_CPUS, run @fn() first on the calling cpu, and then
|
||||
* concurrently on all the other cpus
|
||||
* if @cpu == ALL_CPUS, run @fn() on every online CPU.
|
||||
*
|
||||
* Description: This causes a thread to be scheduled on every other cpu,
|
||||
* each of which disables interrupts, and finally interrupts are disabled
|
||||
* on the current CPU. The result is that noone is holding a spinlock
|
||||
* or inside any other preempt-disabled region when @fn() runs.
|
||||
* Description: This causes a thread to be scheduled on every cpu,
|
||||
* each of which disables interrupts. The result is that noone is
|
||||
* holding a spinlock or inside any other preempt-disabled region when
|
||||
* @fn() runs.
|
||||
*
|
||||
* This can be thought of as a very heavy write lock, equivalent to
|
||||
* grabbing every spinlock in the kernel. */
|
||||
|
@ -35,13 +34,10 @@ int stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu);
|
|||
* @data: the data ptr for the @fn
|
||||
* @cpu: the cpu to run @fn on (or any, if @cpu == NR_CPUS.
|
||||
*
|
||||
* Description: This is a special version of the above, which returns the
|
||||
* thread which has run @fn(): kthread_stop will return the return value
|
||||
* of @fn(). Used by hotplug cpu.
|
||||
* Description: This is a special version of the above, which assumes cpus
|
||||
* won't come or go while it's being called. Used by hotplug cpu.
|
||||
*/
|
||||
struct task_struct *__stop_machine_run(int (*fn)(void *), void *data,
|
||||
unsigned int cpu);
|
||||
|
||||
int __stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu);
|
||||
#else
|
||||
|
||||
static inline int stop_machine_run(int (*fn)(void *), void *data,
|
||||
|
|
13
kernel/cpu.c
13
kernel/cpu.c
|
@ -216,7 +216,6 @@ static int __ref take_cpu_down(void *_param)
|
|||
static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
|
||||
{
|
||||
int err, nr_calls = 0;
|
||||
struct task_struct *p;
|
||||
cpumask_t old_allowed, tmp;
|
||||
void *hcpu = (void *)(long)cpu;
|
||||
unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
|
||||
|
@ -250,19 +249,15 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
|
|||
cpu_clear(cpu, tmp);
|
||||
set_cpus_allowed_ptr(current, &tmp);
|
||||
|
||||
p = __stop_machine_run(take_cpu_down, &tcd_param, cpu);
|
||||
err = __stop_machine_run(take_cpu_down, &tcd_param, cpu);
|
||||
|
||||
if (IS_ERR(p) || cpu_online(cpu)) {
|
||||
if (err || cpu_online(cpu)) {
|
||||
/* CPU didn't die: tell everyone. Can't complain. */
|
||||
if (raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,
|
||||
hcpu) == NOTIFY_BAD)
|
||||
BUG();
|
||||
|
||||
if (IS_ERR(p)) {
|
||||
err = PTR_ERR(p);
|
||||
goto out_allowed;
|
||||
}
|
||||
goto out_thread;
|
||||
goto out_allowed;
|
||||
}
|
||||
|
||||
/* Wait for it to sleep (leaving idle task). */
|
||||
|
@ -279,8 +274,6 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
|
|||
|
||||
check_for_tasks(cpu);
|
||||
|
||||
out_thread:
|
||||
err = kthread_stop(p);
|
||||
out_allowed:
|
||||
set_cpus_allowed_ptr(current, &old_allowed);
|
||||
out_release:
|
||||
|
|
|
@ -1,4 +1,4 @@
|
|||
/* Copyright 2005 Rusty Russell rusty@rustcorp.com.au IBM Corporation.
|
||||
/* Copyright 2008, 2005 Rusty Russell rusty@rustcorp.com.au IBM Corporation.
|
||||
* GPL v2 and any later version.
|
||||
*/
|
||||
#include <linux/cpu.h>
|
||||
|
@ -13,220 +13,177 @@
|
|||
#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. */
|
||||
/* This controls the threads on each CPU. */
|
||||
enum stopmachine_state {
|
||||
STOPMACHINE_WAIT,
|
||||
/* Dummy starting state for thread. */
|
||||
STOPMACHINE_NONE,
|
||||
/* Awaiting everyone to be scheduled. */
|
||||
STOPMACHINE_PREPARE,
|
||||
/* Disable interrupts. */
|
||||
STOPMACHINE_DISABLE_IRQ,
|
||||
/* Run the function */
|
||||
STOPMACHINE_RUN,
|
||||
/* Exit */
|
||||
STOPMACHINE_EXIT,
|
||||
};
|
||||
static enum stopmachine_state state;
|
||||
|
||||
struct stop_machine_data {
|
||||
int (*fn)(void *);
|
||||
void *data;
|
||||
struct completion done;
|
||||
int run_all;
|
||||
} smdata;
|
||||
int fnret;
|
||||
};
|
||||
|
||||
static enum stopmachine_state stopmachine_state;
|
||||
static unsigned int stopmachine_num_threads;
|
||||
static atomic_t stopmachine_thread_ack;
|
||||
/* Like num_online_cpus(), but hotplug cpu uses us, so we need this. */
|
||||
static unsigned int num_threads;
|
||||
static atomic_t thread_ack;
|
||||
static struct completion finished;
|
||||
static DEFINE_MUTEX(lock);
|
||||
|
||||
static int stopmachine(void *cpu)
|
||||
static void set_state(enum stopmachine_state newstate)
|
||||
{
|
||||
int irqs_disabled = 0;
|
||||
int prepared = 0;
|
||||
int ran = 0;
|
||||
cpumask_of_cpu_ptr(cpumask, (int)(long)cpu);
|
||||
/* Reset ack counter. */
|
||||
atomic_set(&thread_ack, num_threads);
|
||||
smp_wmb();
|
||||
state = newstate;
|
||||
}
|
||||
|
||||
set_cpus_allowed_ptr(current, cpumask);
|
||||
/* Last one to ack a state moves to the next state. */
|
||||
static void ack_state(void)
|
||||
{
|
||||
if (atomic_dec_and_test(&thread_ack)) {
|
||||
/* If we're the last one to ack the EXIT, we're finished. */
|
||||
if (state == STOPMACHINE_EXIT)
|
||||
complete(&finished);
|
||||
else
|
||||
set_state(state + 1);
|
||||
}
|
||||
}
|
||||
|
||||
/* Ack: we are alive */
|
||||
smp_mb(); /* Theoretically the ack = 0 might not be on this CPU yet. */
|
||||
atomic_inc(&stopmachine_thread_ack);
|
||||
/* This is the actual thread which stops the CPU. It exits by itself rather
|
||||
* than waiting for kthread_stop(), because it's easier for hotplug CPU. */
|
||||
static int stop_cpu(struct stop_machine_data *smdata)
|
||||
{
|
||||
enum stopmachine_state curstate = STOPMACHINE_NONE;
|
||||
int uninitialized_var(ret);
|
||||
|
||||
/* 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);
|
||||
} else if (stopmachine_state == STOPMACHINE_RUN && !ran) {
|
||||
smdata.fn(smdata.data);
|
||||
ran = 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();
|
||||
do {
|
||||
/* Chill out and ensure we re-read stopmachine_state. */
|
||||
cpu_relax();
|
||||
}
|
||||
if (state != curstate) {
|
||||
curstate = state;
|
||||
switch (curstate) {
|
||||
case STOPMACHINE_DISABLE_IRQ:
|
||||
local_irq_disable();
|
||||
hard_irq_disable();
|
||||
break;
|
||||
case STOPMACHINE_RUN:
|
||||
/* |= allows error detection if functions on
|
||||
* multiple CPUs. */
|
||||
smdata->fnret |= smdata->fn(smdata->data);
|
||||
break;
|
||||
default:
|
||||
break;
|
||||
}
|
||||
ack_state();
|
||||
}
|
||||
} while (curstate != STOPMACHINE_EXIT);
|
||||
|
||||
/* 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();
|
||||
local_irq_enable();
|
||||
do_exit(0);
|
||||
}
|
||||
|
||||
/* Callback for CPUs which aren't supposed to do anything. */
|
||||
static int chill(void *unused)
|
||||
{
|
||||
return 0;
|
||||
}
|
||||
|
||||
/* Change the thread state */
|
||||
static void stopmachine_set_state(enum stopmachine_state state)
|
||||
int __stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu)
|
||||
{
|
||||
atomic_set(&stopmachine_thread_ack, 0);
|
||||
smp_wmb();
|
||||
stopmachine_state = state;
|
||||
while (atomic_read(&stopmachine_thread_ack) != stopmachine_num_threads)
|
||||
cpu_relax();
|
||||
}
|
||||
int i, err;
|
||||
struct stop_machine_data active, idle;
|
||||
struct task_struct **threads;
|
||||
|
||||
static int stop_machine(void)
|
||||
{
|
||||
int i, ret = 0;
|
||||
active.fn = fn;
|
||||
active.data = data;
|
||||
active.fnret = 0;
|
||||
idle.fn = chill;
|
||||
idle.data = NULL;
|
||||
|
||||
atomic_set(&stopmachine_thread_ack, 0);
|
||||
stopmachine_num_threads = 0;
|
||||
stopmachine_state = STOPMACHINE_WAIT;
|
||||
/* If they don't care which cpu fn runs on, just pick one. */
|
||||
if (cpu == NR_CPUS)
|
||||
cpu = any_online_cpu(cpu_online_map);
|
||||
|
||||
/* This could be too big for stack on large machines. */
|
||||
threads = kcalloc(NR_CPUS, sizeof(threads[0]), GFP_KERNEL);
|
||||
if (!threads)
|
||||
return -ENOMEM;
|
||||
|
||||
/* Set up initial state. */
|
||||
mutex_lock(&lock);
|
||||
init_completion(&finished);
|
||||
num_threads = num_online_cpus();
|
||||
set_state(STOPMACHINE_PREPARE);
|
||||
|
||||
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();
|
||||
}
|
||||
|
||||
static void run_other_cpus(void)
|
||||
{
|
||||
stopmachine_set_state(STOPMACHINE_RUN);
|
||||
}
|
||||
|
||||
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);
|
||||
if (smdata->run_all)
|
||||
run_other_cpus();
|
||||
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;
|
||||
|
||||
mutex_lock(&stopmachine_mutex);
|
||||
|
||||
smdata.fn = fn;
|
||||
smdata.data = data;
|
||||
smdata.run_all = (cpu == ALL_CPUS) ? 1 : 0;
|
||||
init_completion(&smdata.done);
|
||||
|
||||
smp_wmb(); /* make sure other cpus see smdata updates */
|
||||
|
||||
/* If they don't care which CPU fn runs on, bind to any online one. */
|
||||
if (cpu == NR_CPUS || cpu == ALL_CPUS)
|
||||
cpu = raw_smp_processor_id();
|
||||
|
||||
p = kthread_create(do_stop, &smdata, "kstopmachine");
|
||||
if (!IS_ERR(p)) {
|
||||
struct stop_machine_data *smdata;
|
||||
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, ¶m);
|
||||
kthread_bind(p, cpu);
|
||||
wake_up_process(p);
|
||||
wait_for_completion(&smdata.done);
|
||||
if (cpu == ALL_CPUS || i == cpu)
|
||||
smdata = &active;
|
||||
else
|
||||
smdata = &idle;
|
||||
|
||||
threads[i] = kthread_create((void *)stop_cpu, smdata, "kstop%u",
|
||||
i);
|
||||
if (IS_ERR(threads[i])) {
|
||||
err = PTR_ERR(threads[i]);
|
||||
threads[i] = NULL;
|
||||
goto kill_threads;
|
||||
}
|
||||
|
||||
/* Place it onto correct cpu. */
|
||||
kthread_bind(threads[i], i);
|
||||
|
||||
/* Make it highest prio. */
|
||||
if (sched_setscheduler_nocheck(threads[i], SCHED_FIFO, ¶m))
|
||||
BUG();
|
||||
}
|
||||
mutex_unlock(&stopmachine_mutex);
|
||||
return p;
|
||||
|
||||
/* We've created all the threads. Wake them all: hold this CPU so one
|
||||
* doesn't hit this CPU until we're ready. */
|
||||
cpu = get_cpu();
|
||||
for_each_online_cpu(i)
|
||||
wake_up_process(threads[i]);
|
||||
|
||||
/* This will release the thread on our CPU. */
|
||||
put_cpu();
|
||||
wait_for_completion(&finished);
|
||||
mutex_unlock(&lock);
|
||||
|
||||
kfree(threads);
|
||||
|
||||
return active.fnret;
|
||||
|
||||
kill_threads:
|
||||
for_each_online_cpu(i)
|
||||
if (threads[i])
|
||||
kthread_stop(threads[i]);
|
||||
mutex_unlock(&lock);
|
||||
|
||||
kfree(threads);
|
||||
return err;
|
||||
}
|
||||
|
||||
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);
|
||||
ret = __stop_machine_run(fn, data, cpu);
|
||||
put_online_cpus();
|
||||
|
||||
return ret;
|
||||
|
|
Loading…
Reference in New Issue
Block a user