linux-kernel - [tip:smp/hotplug] x86/mtrr: Remove get_online_cpus() from mtrr_save

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Date:   Fri, 26 May 2017 01:35:36 -0700
From:   tip-bot for Sebastian Andrzej Siewior <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     rostedt@...dmis.org, bigeasy@...utronix.de, hpa@...or.com,
        linux-kernel@...r.kernel.org, mingo@...nel.org, tglx@...utronix.de,
        paulmck@...ux.vnet.ibm.com, peterz@...radead.org
Subject: [tip:smp/hotplug] x86/mtrr: Remove get_online_cpus() from
 mtrr_save_state()

Commit-ID:  547efeadd42a3c75e41e33c0637cba100fc18289
Gitweb:     http://git.kernel.org/tip/547efeadd42a3c75e41e33c0637cba100fc18289
Author:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
AuthorDate: Wed, 24 May 2017 10:15:19 +0200
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Fri, 26 May 2017 10:10:38 +0200

x86/mtrr: Remove get_online_cpus() from mtrr_save_state()

mtrr_save_state() is invoked from native_cpu_up() which is in the context
of a CPU hotplug operation and therefor calling get_online_cpus() is
pointless.

While this works in the current get_online_cpus() implementation it
prevents from converting the hotplug locking to percpu rwsems.

Remove it.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Tested-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Acked-by: Ingo Molnar <mingo@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Steven Rostedt <rostedt@...dmis.org>
Link: http://lkml.kernel.org/r/20170524081547.651378834@linutronix.de

---
 arch/x86/kernel/cpu/mtrr/main.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c
index 2bce84d..c5bb63b 100644
--- a/arch/x86/kernel/cpu/mtrr/main.c
+++ b/arch/x86/kernel/cpu/mtrr/main.c
@@ -807,10 +807,8 @@ void mtrr_save_state(void)
 	if (!mtrr_enabled())
 		return;

-	get_online_cpus();
 	first_cpu = cpumask_first(cpu_online_mask);
 	smp_call_function_single(first_cpu, mtrr_save_fixed_ranges, NULL, 1);
-	put_online_cpus();
 }

 void set_mtrr_aps_delayed_init(void)