linux-kernel - [tip:smp/hotplug] arm: Convert VFP hotplug notifiers to state machine

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Date:	Tue, 19 Jul 2016 00:15:41 -0700
From:	tip-bot for Thomas Gleixner <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
	tglx@...utronix.de, hpa@...or.com, anna-maria@...utronix.de,
	peterz@...radead.org, mingo@...nel.org, bigeasy@...utronix.de,
	linux@....linux.org.uk
Subject: [tip:smp/hotplug] arm: Convert VFP hotplug notifiers to state
 machine

Commit-ID:  e5b61bafe70477e05e1dce0d6ca4ec181e23cb2a
Gitweb:     http://git.kernel.org/tip/e5b61bafe70477e05e1dce0d6ca4ec181e23cb2a
Author:     Thomas Gleixner <tglx@...utronix.de>
AuthorDate: Wed, 13 Jul 2016 17:16:35 +0000
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Fri, 15 Jul 2016 10:40:22 +0200

arm: Convert VFP hotplug notifiers to state machine

Straight forward conversion plus commentary why code which is executed
in hotplug callbacks needs to be invoked before installing them.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Anna-Maria Gleixner <anna-maria@...utronix.de>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Russell King <linux@....linux.org.uk>
Cc: linux-arm-kernel@...ts.infradead.org
Cc: rt@...utronix.de
Link: http://lkml.kernel.org/r/20160713153335.713612993@linutronix.de
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/arm/vfp/vfpmodule.c   | 28 +++++++++++++++++-----------
 include/linux/cpuhotplug.h |  1 +
 2 files changed, 18 insertions(+), 11 deletions(-)

diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
index 73085d3..da0b33d 100644
--- a/arch/arm/vfp/vfpmodule.c
+++ b/arch/arm/vfp/vfpmodule.c
@@ -643,19 +643,19 @@ int vfp_restore_user_hwstate(struct user_vfp __user *ufp,
  * hardware state at every thread switch.  We clear our held state when
  * a CPU has been killed, indicating that the VFP hardware doesn't contain
  * a threads VFP state.  When a CPU starts up, we re-enable access to the
- * VFP hardware.
- *
- * Both CPU_DYING and CPU_STARTING are called on the CPU which
+ * VFP hardware. The callbacks below are called on the CPU which
  * is being offlined/onlined.
  */
-static int vfp_hotplug(struct notifier_block *b, unsigned long action,
-	void *hcpu)
+static int vfp_dying_cpu(unsigned int cpu)
 {
-	if (action == CPU_DYING || action == CPU_DYING_FROZEN)
-		vfp_current_hw_state[(long)hcpu] = NULL;
-	else if (action == CPU_STARTING || action == CPU_STARTING_FROZEN)
-		vfp_enable(NULL);
-	return NOTIFY_OK;
+	vfp_force_reload(cpu, current_thread_info());
+	return 0;
+}
+
+static int vfp_starting_cpu(unsigned int unused)
+{
+	vfp_enable(NULL);
+	return 0;
 }
 
 void vfp_kmode_exception(void)
@@ -732,6 +732,10 @@ static int __init vfp_init(void)
 	unsigned int vfpsid;
 	unsigned int cpu_arch = cpu_architecture();
 
+	/*
+	 * Enable the access to the VFP on all online CPUs so the
+	 * following test on FPSID will succeed.
+	 */
 	if (cpu_arch >= CPU_ARCH_ARMv6)
 		on_each_cpu(vfp_enable, NULL, 1);
 
@@ -794,7 +798,9 @@ static int __init vfp_init(void)
 		VFP_arch = (vfpsid & FPSID_ARCH_MASK) >> FPSID_ARCH_BIT;
 	}
 
-	hotcpu_notifier(vfp_hotplug, 0);
+	cpuhp_setup_state_nocalls(CPUHP_AP_ARM_VFP_STARTING,
+				  "AP_ARM_VFP_STARTING", vfp_starting_cpu,
+				  vfp_dying_cpu);
 
 	vfp_vector = vfp_support_entry;
 
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 3e719ba..4c63cb3 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -34,6 +34,7 @@ enum cpuhp_state {
 	CPUHP_AP_PERF_X86_CQM_STARTING,
 	CPUHP_AP_PERF_X86_CSTATE_STARTING,
 	CPUHP_AP_PERF_XTENSA_STARTING,
+	CPUHP_AP_ARM_VFP_STARTING,
 	CPUHP_AP_NOTIFY_STARTING,
 	CPUHP_AP_ONLINE,
 	CPUHP_TEARDOWN_CPU,