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stop_machine: reimplement using cpu_stop

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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: Tejun Heo <[email protected]>
Acked-by: Rusty Russell <[email protected]>
Acked-by: Peter Zijlstra <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Dimitri Sivanich <[email protected]>
This commit is contained in:
Tejun Heo 2010-05-06 18:49:20 +02:00
commit 3fc1f1e27a
6 changed files with 42 additions and 173 deletions
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14
drivers/xen/manage.c
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@ -80,12 +80,6 @@ static void do_suspend(void)
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
/* If the kernel is preemptible, we need to freeze all the processes
to prevent them from being in the middle of a pagetable update
@ -93,7 +87,7 @@ static void do_suspend(void)
err = freeze_processes();
if (err) {
printk(KERN_ERR "xen suspend: freeze failed %d\n", err);
goto out_destroy_sm;
goto out;
}
#endif
@ -136,12 +130,8 @@ out_resume:
out_thaw:
#ifdef CONFIG_PREEMPT
thaw_processes();
out_destroy_sm:
#endif
stop_machine_destroy();
out:
#endif
shutting_down = SHUTDOWN_INVALID;
}
#endif /* CONFIG_PM_SLEEP */