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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, write to the Free Software Foundation, Inc., 59 Temple
* Place - Suite 330, Boston, MA 02111-1307 USA.
*/
#include <xen/config.h>
#include <xen/init.h>
#include <xen/sched.h>
#include <xen/spinlock.h>
#include <xen/softirq.h>
#include <xen/errno.h>
#include <xen/smp.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 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;
while ( atomic_read(&stopmachine_data.done) != stopmachine_data.nr_cpus )
cpu_relax();
}
int stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu)
{
cpumask_t allbutself;
unsigned int i, nr_cpus;
int ret;
BUG_ON(!local_irq_is_enabled());
allbutself = cpu_online_map;
cpu_clear(smp_processor_id(), allbutself);
nr_cpus = cpus_weight(allbutself);
if ( nr_cpus == 0 )
{
BUG_ON(cpu != smp_processor_id());
return (*fn)(data);
}
/* Note: We shouldn't spin on lock when it's held by others since others
* is expecting this cpus to enter softirq context. Or else deadlock
* is caused.
*/
if ( !spin_trylock(&stopmachine_lock) )
return -EBUSY;
stopmachine_data.fn = fn;
stopmachine_data.fn_data = data;
stopmachine_data.nr_cpus = nr_cpus;
stopmachine_data.fn_cpu = cpu;
atomic_set(&stopmachine_data.done, 0);
stopmachine_data.state = STOPMACHINE_START;
smp_wmb();
for_each_cpu_mask ( i, allbutself )
cpu_raise_softirq(i, STOPMACHINE_SOFTIRQ);
stopmachine_set_state(STOPMACHINE_PREPARE);
local_irq_disable();
stopmachine_set_state(STOPMACHINE_DISABLE_IRQ);
if ( cpu == smp_processor_id() )
stopmachine_data.fn_result = (*fn)(data);
stopmachine_set_state(STOPMACHINE_INVOKE);
ret = stopmachine_data.fn_result;
stopmachine_set_state(STOPMACHINE_EXIT);
local_irq_enable();
spin_unlock(&stopmachine_lock);
return ret;
}
static void stopmachine_softirq(void)
{
enum stopmachine_state state = STOPMACHINE_START;
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_result =
stopmachine_data.fn(stopmachine_data.fn_data);
break;
default:
break;
}
smp_mb();
atomic_inc(&stopmachine_data.done);
}
local_irq_enable();
}
static int __init cpu_stopmachine_init(void)
{
open_softirq(STOPMACHINE_SOFTIRQ, stopmachine_softirq);
return 0;
}
__initcall(cpu_stopmachine_init);
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