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: Tejun Heo <tj@kernel.org>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Dimitri Sivanich <sivanich@sgi.com>
diff --git a/drivers/xen/manage.c b/drivers/xen/manage.c
index 2ac4440..8943b8c 100644
--- a/drivers/xen/manage.c
+++ b/drivers/xen/manage.c
@@ -80,12 +80,6 @@
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 @@
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_thaw:
#ifdef CONFIG_PREEMPT
thaw_processes();
-
-out_destroy_sm:
-#endif
- stop_machine_destroy();
-
out:
+#endif
shutting_down = SHUTDOWN_INVALID;
}
#endif /* CONFIG_PM_SLEEP */