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/******************************************************************************
* common/stop_machine.c
*
* Facilities to put whole machine in a safe 'stop' state
*
* Copyright 2005 Rusty Russell rusty@rustcorp.com.au IBM Corporation
* Copyright 2008 Kevin Tian <kevin.tian@intel.com>, Intel Corporation.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms and conditions of the GNU General Public License,
* version 2, as published by the Free Software Foundation.
*
* This program is distributed in the hope it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*
* You should have received a copy of the GNU General Public License along with
* this program; If not, see <http://www.gnu.org/licenses/>.
*/
#include <xen/init.h>
#include <xen/sched.h>
#include <xen/spinlock.h>
#include <xen/tasklet.h>
#include <xen/stop_machine.h>
#include <xen/errno.h>
#include <xen/smp.h>
#include <xen/cpu.h>
#include <asm/current.h>
#include <asm/processor.h>
enum stopmachine_state {
STOPMACHINE_START,
STOPMACHINE_PREPARE,
STOPMACHINE_DISABLE_IRQ,
STOPMACHINE_INVOKE,
STOPMACHINE_EXIT
};
struct stopmachine_data {
unsigned int nr_cpus;
enum stopmachine_state state;
atomic_t done;
unsigned int fn_cpu;
int fn_result;
int (*fn)(void *);
void *fn_data;
};
static DEFINE_PER_CPU(struct tasklet, stopmachine_tasklet);
static struct stopmachine_data stopmachine_data;
static DEFINE_SPINLOCK(stopmachine_lock);
static void stopmachine_set_state(enum stopmachine_state state)
{
atomic_set(&stopmachine_data.done, 0);
smp_wmb();
stopmachine_data.state = state;
}
static void stopmachine_wait_state(void)
{
while ( atomic_read(&stopmachine_data.done) != stopmachine_data.nr_cpus )
cpu_relax();
}
/*
* Sync all processors and call a function on one or all of them.
* As stop_machine_run() is using a tasklet for syncing the processors it is
* mandatory to be called only on an idle vcpu, as otherwise active core
* scheduling might hang.
*/
int stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu)
{
unsigned int i, nr_cpus;
unsigned int this = smp_processor_id();
int ret;
BUG_ON(!local_irq_is_enabled());
BUG_ON(!is_idle_vcpu(current));
/* cpu_online_map must not change. */
if ( !get_cpu_maps() )
return -EBUSY;
nr_cpus = num_online_cpus();
if ( cpu_online(this) )
nr_cpus--;
/* Must not spin here as the holder will expect us to be descheduled. */
if ( !spin_trylock(&stopmachine_lock) )
{
put_cpu_maps();
return -EBUSY;
}
stopmachine_data.fn = fn;
stopmachine_data.fn_data = data;
stopmachine_data.nr_cpus = nr_cpus;
stopmachine_data.fn_cpu = cpu;
stopmachine_data.fn_result = 0;
atomic_set(&stopmachine_data.done, 0);
stopmachine_data.state = STOPMACHINE_START;
smp_wmb();
for_each_online_cpu ( i )
if ( i != this )
tasklet_schedule_on_cpu(&per_cpu(stopmachine_tasklet, i), i);
stopmachine_set_state(STOPMACHINE_PREPARE);
stopmachine_wait_state();
local_irq_disable();
stopmachine_set_state(STOPMACHINE_DISABLE_IRQ);
stopmachine_wait_state();
spin_debug_disable();
stopmachine_set_state(STOPMACHINE_INVOKE);
if ( (cpu == this) || (cpu == NR_CPUS) )
{
ret = (*fn)(data);
if ( ret )
write_atomic(&stopmachine_data.fn_result, ret);
}
stopmachine_wait_state();
ret = stopmachine_data.fn_result;
spin_debug_enable();
stopmachine_set_state(STOPMACHINE_EXIT);
stopmachine_wait_state();
local_irq_enable();
spin_unlock(&stopmachine_lock);
put_cpu_maps();
return ret;
}
static void cf_check stopmachine_action(void *data)
{
unsigned int cpu = (unsigned long)data;
enum stopmachine_state state = STOPMACHINE_START;
BUG_ON(cpu != smp_processor_id());
smp_mb();
while ( state != STOPMACHINE_EXIT )
{
while ( stopmachine_data.state == state )
cpu_relax();
state = stopmachine_data.state;
switch ( state )
{
case STOPMACHINE_DISABLE_IRQ:
local_irq_disable();
break;
case STOPMACHINE_INVOKE:
if ( (stopmachine_data.fn_cpu == smp_processor_id()) ||
(stopmachine_data.fn_cpu == NR_CPUS) )
{
int ret = stopmachine_data.fn(stopmachine_data.fn_data);
if ( ret )
write_atomic(&stopmachine_data.fn_result, ret);
}
break;
default:
break;
}
smp_mb();
atomic_inc(&stopmachine_data.done);
}
local_irq_enable();
}
static int cf_check cpu_callback(
struct notifier_block *nfb, unsigned long action, void *hcpu)
{
unsigned int cpu = (unsigned long)hcpu;
if ( action == CPU_UP_PREPARE )
tasklet_init(&per_cpu(stopmachine_tasklet, cpu),
stopmachine_action, hcpu);
return NOTIFY_DONE;
}
static struct notifier_block cpu_nfb = {
.notifier_call = cpu_callback
};
static int __init cf_check cpu_stopmachine_init(void)
{
unsigned int cpu;
for_each_online_cpu ( cpu )
{
void *hcpu = (void *)(long)cpu;
cpu_callback(&cpu_nfb, CPU_UP_PREPARE, hcpu);
}
register_cpu_notifier(&cpu_nfb);
return 0;
}
__initcall(cpu_stopmachine_init);
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