s390/kernel: Use stop_machine_cpuslocked()

stp_work_fn() holds get_online_cpus() while invoking stop_machine().

stop_machine() invokes get_online_cpus() as well. This is correct, but
prevents the conversion of the hotplug locking to a percpu rwsem.

Use stop_machine_cpuslocked() to avoid the nested call. Convert
*_online_cpus() to the new interfaces while at it.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: linux-s390@vger.kernel.org
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: David Hildenbrand <dahi@linux.vnet.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Link: http://lkml.kernel.org/r/20170524081548.250203087@linutronix.de

diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
index c3a52f9a69a0596102ff2066133678cc96ea5a4e..192efdfac91829c49a6f41e04c9e3b601c84c0f7 100644 (file)
--- a/arch/s390/kernel/time.c
+++ b/arch/s390/kernel/time.c
@@ -636,10 +636,10 @@ static void stp_work_fn(struct work_struct *work)
                goto out_unlock;
 
        memset(&stp_sync, 0, sizeof(stp_sync));
-       get_online_cpus();
+       cpus_read_lock();
        atomic_set(&stp_sync.cpus, num_online_cpus() - 1);
-       stop_machine(stp_sync_clock, &stp_sync, cpu_online_mask);
-       put_online_cpus();
+       stop_machine_cpuslocked(stp_sync_clock, &stp_sync, cpu_online_mask);
+       cpus_read_unlock();
 
        if (!check_sync_clock())
                /*