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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@linutronix.de>
AuthorDate: Wed, 13 Jul 2016 17:16:35 +0000
Committer: Ingo Molnar <mingo@kernel.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@linutronix.de>
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: linux-arm-kernel@lists.infradead.org
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160713153335.713612993@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.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,
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