linux-kernel - [tip:smp/hotplug] s390/kernel: Use stop_machine

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Date:   Fri, 26 May 2017 01:39:29 -0700
From:   tip-bot for Sebastian Andrzej Siewior <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     rostedt@...dmis.org, mingo@...nel.org, tglx@...utronix.de,
        heiko.carstens@...ibm.com, bigeasy@...utronix.de, hpa@...or.com,
        linux-kernel@...r.kernel.org, dahi@...ux.vnet.ibm.com,
        schwidefsky@...ibm.com, peterz@...radead.org,
        paulmck@...ux.vnet.ibm.com
Subject: [tip:smp/hotplug] s390/kernel: Use stop_machine_cpuslocked()

Commit-ID:  2337e879e8805a630b418f3e73a98084d4724b83
Gitweb:     http://git.kernel.org/tip/2337e879e8805a630b418f3e73a98084d4724b83
Author:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
AuthorDate: Wed, 24 May 2017 10:15:26 +0200
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Fri, 26 May 2017 10:10:41 +0200

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

---
 arch/s390/kernel/time.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
index c3a52f9..192efdf 100644
--- 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())
 		/*