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Commit 3fc1f1e2 authored by Tejun Heo's avatar Tejun Heo
Browse files

stop_machine: reimplement using cpu_stop 



Reimplement stop_machine using cpu_stop.  As cpu stoppers are
guaranteed to be available for all online cpus,
stop_machine_create/destroy() are no longer necessary and removed.

With resource management and synchronization handled by cpu_stop, the
new implementation is much simpler.  Asking the cpu_stop to execute
the stop_cpu() state machine on all online cpus with cpu hotplug
disabled is enough.

stop_machine itself doesn't need to manage any global resources
anymore, so all per-instance information is rolled into struct
stop_machine_data and the mutex and all static data variables are
removed.

The previous implementation created and destroyed RT workqueues as
necessary which made stop_machine() calls highly expensive on very
large machines.  According to Dimitri Sivanich, preventing the dynamic
creation/destruction makes booting faster more than twice on very
large machines.  cpu_stop resources are preallocated for all online
cpus and should have the same effect.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarRusty Russell <rusty@rustcorp.com.au>
Acked-by: default avatarPeter Zijlstra <peterz@infradead.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Dimitri Sivanich <sivanich@sgi.com>
parent 1142d810

arch/s390/kernel/time.c

+0 −1
Original line number Original line Diff line number Diff line
@@ -390,7 +390,6 @@ static void __init time_init_wq(void) 
	if (time_sync_wq)

	if (time_sync_wq)

		return;

		return;

	time_sync_wq = create_singlethread_workqueue("timesync");

	time_sync_wq = create_singlethread_workqueue("timesync");

	stop_machine_create();

}

}





/*

/*

drivers/xen/manage.c

+2 −12
Original line number Original line Diff line number Diff line
@@ -80,12 +80,6 @@ static void do_suspend(void) 




	shutting_down = SHUTDOWN_SUSPEND;

	shutting_down = SHUTDOWN_SUSPEND;





	err = stop_machine_create();

	if (err) {

		printk(KERN_ERR "xen suspend: failed to setup stop_machine %d\n", err);

		goto out;

	}



#ifdef CONFIG_PREEMPT

#ifdef CONFIG_PREEMPT

	/* If the kernel is preemptible, we need to freeze all the processes

	/* If the kernel is preemptible, we need to freeze all the processes

	   to prevent them from being in the middle of a pagetable update

	   to prevent them from being in the middle of a pagetable update
@@ -93,7 +87,7 @@ static void do_suspend(void) 
	err = freeze_processes();

	err = freeze_processes();

	if (err) {

	if (err) {

		printk(KERN_ERR "xen suspend: freeze failed %d\n", err);

		printk(KERN_ERR "xen suspend: freeze failed %d\n", err);

		goto out_destroy_sm;

		goto out;

	}

	}

#endif

#endif
@@ -136,12 +130,8 @@ static void do_suspend(void) 
out_thaw:

out_thaw:

#ifdef CONFIG_PREEMPT

#ifdef CONFIG_PREEMPT

	thaw_processes();

	thaw_processes();



out_destroy_sm:

#endif

	stop_machine_destroy();



out:

out:

#endif

	shutting_down = SHUTDOWN_INVALID;

	shutting_down = SHUTDOWN_INVALID;

}

}

#endif	/* CONFIG_PM_SLEEP */

#endif	/* CONFIG_PM_SLEEP */

include/linux/stop_machine.h

+0 −20
Original line number Original line Diff line number Diff line
@@ -67,23 +67,6 @@ int stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus); 
 */

 */

int __stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus);

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

#else





static inline int stop_machine(int (*fn)(void *), void *data,

static inline int stop_machine(int (*fn)(void *), void *data,
@@ -96,8 +79,5 @@ static inline int stop_machine(int (*fn)(void *), void *data, 
	return ret;

	return ret;

}

}





static inline int stop_machine_create(void) { return 0; }

static inline void stop_machine_destroy(void) { }



#endif /* CONFIG_SMP */

#endif /* CONFIG_SMP */

#endif /* _LINUX_STOP_MACHINE */
 
#endif /* _LINUX_STOP_MACHINE */

kernel/cpu.c

+0 −8
Original line number Original line Diff line number Diff line
@@ -266,9 +266,6 @@ int __ref cpu_down(unsigned int cpu) 
{

{

	int err;

	int err;





	err = stop_machine_create();

	if (err)

		return err;

	cpu_maps_update_begin();

	cpu_maps_update_begin();





	if (cpu_hotplug_disabled) {

	if (cpu_hotplug_disabled) {
@@ -280,7 +277,6 @@ int __ref cpu_down(unsigned int cpu) 




out:

out:

	cpu_maps_update_done();

	cpu_maps_update_done();

	stop_machine_destroy();

	return err;

	return err;

}

}

EXPORT_SYMBOL(cpu_down);

EXPORT_SYMBOL(cpu_down);
@@ -361,9 +357,6 @@ int disable_nonboot_cpus(void) 
{

{

	int cpu, first_cpu, error;

	int cpu, first_cpu, error;





	error = stop_machine_create();

	if (error)

		return error;

	cpu_maps_update_begin();

	cpu_maps_update_begin();

	first_cpu = cpumask_first(cpu_online_mask);

	first_cpu = cpumask_first(cpu_online_mask);

	/*

	/*
@@ -394,7 +387,6 @@ int disable_nonboot_cpus(void) 
		printk(KERN_ERR "Non-boot CPUs are not disabled\n");

		printk(KERN_ERR "Non-boot CPUs are not disabled\n");

	}

	}

	cpu_maps_update_done();

	cpu_maps_update_done();

	stop_machine_destroy();

	return error;

	return error;

}

}

kernel/module.c

+2 −12
Original line number Original line Diff line number Diff line
@@ -723,16 +723,8 @@ SYSCALL_DEFINE2(delete_module, const char __user *, name_user, 
		return -EFAULT;

		return -EFAULT;

	name[MODULE_NAME_LEN-1] = '\0';

	name[MODULE_NAME_LEN-1] = '\0';





	/* Create stop_machine threads since free_module relies on

	if (mutex_lock_interruptible(&module_mutex) != 0)

	 * a non-failing stop_machine call. */

		return -EINTR;

	ret = stop_machine_create();

	if (ret)

		return ret;



	if (mutex_lock_interruptible(&module_mutex) != 0) {

		ret = -EINTR;

		goto out_stop;

	}





	mod = find_module(name);

	mod = find_module(name);

	if (!mod) {

	if (!mod) {
@@ -792,8 +784,6 @@ SYSCALL_DEFINE2(delete_module, const char __user *, name_user, 




 out:

 out:

	mutex_unlock(&module_mutex);

	mutex_unlock(&module_mutex);

out_stop:

	stop_machine_destroy();

	return ret;

	return ret;

}

}