linux-kernel - [tip:locking/core] clocksource/arm_arch_timer: Use static_branch_enable

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Date:   Thu, 10 Aug 2017 05:15:09 -0700
From:   tip-bot for Marc Zyngier <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     peterz@...radead.org, hpa@...or.com, tglx@...utronix.de,
        mingo@...nel.org, marc.zyngier@....com, leo.yan@...aro.org,
        torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: [tip:locking/core] clocksource/arm_arch_timer: Use
 static_branch_enable_cpuslocked()

Commit-ID:  450f9689f294c331c56ec37d68302ccc19c7caa2
Gitweb:     http://git.kernel.org/tip/450f9689f294c331c56ec37d68302ccc19c7caa2
Author:     Marc Zyngier <marc.zyngier@....com>
AuthorDate: Tue, 1 Aug 2017 09:02:57 +0100
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 10 Aug 2017 12:29:00 +0200

clocksource/arm_arch_timer: Use static_branch_enable_cpuslocked()

Use the new static_branch_enable_cpuslocked() function to switch
the workaround static key on the CPU hotplug path.

Signed-off-by: Marc Zyngier <marc.zyngier@....com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Leo Yan <leo.yan@...aro.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: linux-arm-kernel@...ts.infradead.org
Link: http://lkml.kernel.org/r/20170801080257.5056-5-marc.zyngier@arm.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 drivers/clocksource/arm_arch_timer.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index aae87c4..c62e716 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -455,7 +455,11 @@ void arch_timer_enable_workaround(const struct arch_timer_erratum_workaround *wa
 			per_cpu(timer_unstable_counter_workaround, i) = wa;
 	}
 
-	static_branch_enable(&arch_timer_read_ool_enabled);
+	/*
+	 * Use the locked version, as we're called from the CPU
+	 * hotplug framework. Otherwise, we end-up in deadlock-land.
+	 */
+	static_branch_enable_cpuslocked(&arch_timer_read_ool_enabled);
 
 	/*
 	 * Don't use the vdso fastpath if errata require using the