9ea09af3bd
Introduce stop_machine_create/destroy. With this interface subsystems that need a non-failing stop_machine environment can create the stop_machine machine threads before actually calling stop_machine. When the threads aren't needed anymore they can be killed with stop_machine_destroy again. When stop_machine gets called and the threads aren't present they will be created and destroyed automatically. This restores the old behaviour of stop_machine. This patch also converts cpu hotplug to the new interface since it is special: cpu_down calls __stop_machine instead of stop_machine. However the kstop threads will only be created when stop_machine gets called. Changing the code so that the threads would be created automatically on __stop_machine is currently not possible: when __stop_machine gets called we hold cpu_add_remove_lock, which is the same lock that create_rt_workqueue would take. So the workqueue needs to be created before the cpu hotplug code locks cpu_add_remove_lock. Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
73 lines
2.3 KiB
C
73 lines
2.3 KiB
C
#ifndef _LINUX_STOP_MACHINE
|
|
#define _LINUX_STOP_MACHINE
|
|
/* "Bogolock": stop the entire machine, disable interrupts. This is a
|
|
very heavy lock, which is equivalent to grabbing every spinlock
|
|
(and more). So the "read" side to such a lock is anything which
|
|
disables preeempt. */
|
|
#include <linux/cpu.h>
|
|
#include <linux/cpumask.h>
|
|
#include <asm/system.h>
|
|
|
|
#if defined(CONFIG_STOP_MACHINE) && defined(CONFIG_SMP)
|
|
|
|
/**
|
|
* stop_machine: freeze the machine on all CPUs and run this function
|
|
* @fn: the function to run
|
|
* @data: the data ptr for the @fn()
|
|
* @cpus: the cpus to run the @fn() on (NULL = any online cpu)
|
|
*
|
|
* 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. */
|
|
int stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus);
|
|
|
|
/**
|
|
* __stop_machine: freeze the machine on all CPUs and run this function
|
|
* @fn: the function to run
|
|
* @data: the data ptr for the @fn
|
|
* @cpus: the cpus to run the @fn() on (NULL = any online 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.
|
|
*/
|
|
int __stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus);
|
|
|
|
/**
|
|
* stop_machine_create: create all stop_machine threads
|
|
*
|
|
* Description: This causes all stop_machine threads to be created before
|
|
* stop_machine actually gets called. This can be used by subsystems that
|
|
* need a non failing stop_machine infrastructure.
|
|
*/
|
|
int stop_machine_create(void);
|
|
|
|
/**
|
|
* stop_machine_destroy: destroy all stop_machine threads
|
|
*
|
|
* Description: This causes all stop_machine threads which were created with
|
|
* stop_machine_create to be destroyed again.
|
|
*/
|
|
void stop_machine_destroy(void);
|
|
|
|
#else
|
|
|
|
static inline int stop_machine(int (*fn)(void *), void *data,
|
|
const struct cpumask *cpus)
|
|
{
|
|
int ret;
|
|
local_irq_disable();
|
|
ret = fn(data);
|
|
local_irq_enable();
|
|
return ret;
|
|
}
|
|
|
|
static inline int stop_machine_create(void) { return 0; }
|
|
static inline void stop_machine_destroy(void) { }
|
|
|
|
#endif /* CONFIG_SMP */
|
|
#endif /* _LINUX_STOP_MACHINE */
|