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

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Message-ID: <tip-f9a69931c3959940538884d5962b770c3db75df5@git.kernel.org>
Date:   Fri, 26 May 2017 01:40:02 -0700
From:   tip-bot for Sebastian Andrzej Siewior <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     mpe@...erman.id.au, bigeasy@...utronix.de,
        paulmck@...ux.vnet.ibm.com, hpa@...or.com,
        benh@...nel.crashing.org, rostedt@...dmis.org, mingo@...nel.org,
        peterz@...radead.org, linux-kernel@...r.kernel.org,
        tglx@...utronix.de
Subject: [tip:smp/hotplug] powerpc/powernv: Use stop_machine_cpuslocked()

Commit-ID:  f9a69931c3959940538884d5962b770c3db75df5
Gitweb:     http://git.kernel.org/tip/f9a69931c3959940538884d5962b770c3db75df5
Author:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
AuthorDate: Wed, 24 May 2017 10:15:27 +0200
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Fri, 26 May 2017 10:10:41 +0200

powerpc/powernv: Use stop_machine_cpuslocked()

set_subcores_per_core() 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>
Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Michael Ellerman <mpe@...erman.id.au>
Cc: linuxppc-dev@...ts.ozlabs.org
Link: http://lkml.kernel.org/r/20170524081548.331016542@linutronix.de

---
 arch/powerpc/platforms/powernv/subcore.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/platforms/powernv/subcore.c b/arch/powerpc/platforms/powernv/subcore.c
index 0babef1..e6230f10 100644
--- a/arch/powerpc/platforms/powernv/subcore.c
+++ b/arch/powerpc/platforms/powernv/subcore.c
@@ -348,7 +348,7 @@ static int set_subcores_per_core(int new_mode)
 		state->master = 0;
 	}

-	get_online_cpus();
+	cpus_read_lock();

 	/* This cpu will update the globals before exiting stop machine */
 	this_cpu_ptr(&split_state)->master = 1;
@@ -356,9 +356,10 @@ static int set_subcores_per_core(int new_mode)
 	/* Ensure state is consistent before we call the other cpus */
 	mb();

-	stop_machine(cpu_update_split_mode, &new_mode, cpu_online_mask);
+	stop_machine_cpuslocked(cpu_update_split_mode, &new_mode,
+				cpu_online_mask);

-	put_online_cpus();
+	cpus_read_unlock();

 	return 0;
 }