S390 topology: don't use kthread() for arch_reinit_sched_domains()

Now that it is safe to use get_online_cpus() we can revert

	[S390] cpu topology: Fix possible deadlock.
	commit: fd781fa2

and call arch_reinit_sched_domains() directly from topology_work_fn().
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Gautham R Shenoy <ego@in.ibm.com>
Tested-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Max Krasnyansky <maxk@qualcomm.com>
Cc: Paul Jackson <pj@sgi.com>
Cc: Paul Menage <menage@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Vegard Nossum <vegard.nossum@gmail.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/s390/kernel/topology.c

@@ -9,7 +9,6 @@
 #include <linux/device.h>
 #include <linux/bootmem.h>
 #include <linux/sched.h>
-#include <linux/kthread.h>
 #include <linux/workqueue.h>
 #include <linux/cpu.h>
 #include <linux/smp.h>
@@ -230,20 +229,9 @@ void arch_update_cpu_topology(void)
 	}
 }
 
-static int topology_kthread(void *data)
-{
-	arch_reinit_sched_domains();
-	return 0;
-}
-
 static void topology_work_fn(struct work_struct *work)
 {
-	/* We can't call arch_reinit_sched_domains() from a multi-threaded
-	 * workqueue context since it may deadlock in case of cpu hotplug.
-	 * So we have to create a kernel thread in order to call
-	 * arch_reinit_sched_domains().
-	 */
-	kthread_run(topology_kthread, NULL, "topology_update");
+	arch_reinit_sched_domains();
 }
 
 void topology_schedule_update(void)