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Subject[PATCH 03/20] x86/msr: Convert to hotplug state machine
Date
Install the callbacks via the state machine and let the core invoke
the callbacks on the already online CPUs.

Cc: x86@kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
arch/x86/kernel/msr.c | 56 +++++++++-------------------------------------
include/linux/cpuhotplug.h | 1 +
2 files changed, 11 insertions(+), 46 deletions(-)

diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c
index 7f3550acde1b..43a125b5c5dc 100644
--- a/arch/x86/kernel/msr.c
+++ b/arch/x86/kernel/msr.c
@@ -180,7 +180,7 @@ static const struct file_operations msr_fops = {
.compat_ioctl = msr_ioctl,
};

-static int msr_device_create(int cpu)
+static int msr_device_create(unsigned int cpu)
{
struct device *dev;

@@ -189,34 +189,12 @@ static int msr_device_create(int cpu)
return PTR_ERR_OR_ZERO(dev);
}

-static void msr_device_destroy(int cpu)
+static int msr_device_destroy(unsigned int cpu)
{
device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu));
+ return 0;
}

-static int msr_class_cpu_callback(struct notifier_block *nfb,
- unsigned long action, void *hcpu)
-{
- unsigned int cpu = (unsigned long)hcpu;
- int err = 0;
-
- switch (action) {
- case CPU_UP_PREPARE:
- err = msr_device_create(cpu);
- break;
- case CPU_UP_CANCELED:
- case CPU_UP_CANCELED_FROZEN:
- case CPU_DEAD:
- msr_device_destroy(cpu);
- break;
- }
- return notifier_from_errno(err);
-}
-
-static struct notifier_block __refdata msr_class_cpu_notifier = {
- .notifier_call = msr_class_cpu_callback,
-};
-
static char *msr_devnode(struct device *dev, umode_t *mode)
{
return kasprintf(GFP_KERNEL, "cpu/%u/msr", MINOR(dev->devt));
@@ -224,8 +202,7 @@ static char *msr_devnode(struct device *dev, umode_t *mode)

static int __init msr_init(void)
{
- int i, err = 0;
- i = 0;
+ int err;

if (__register_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr", &msr_fops)) {
pr_err("unable to get major %d for msr\n", MSR_MAJOR);
@@ -239,23 +216,16 @@ static int __init msr_init(void)
}
msr_class->devnode = msr_devnode;

- cpu_notifier_register_begin();
- for_each_online_cpu(i) {
- err = msr_device_create(i);
- if (err != 0)
- goto out_class;
- }
- __register_hotcpu_notifier(&msr_class_cpu_notifier);
- cpu_notifier_register_done();
+ err = cpuhp_setup_state(CPUHP_X86_MSR_PREPARE, "x86/msr:prepare",
+ msr_device_create, msr_device_destroy);
+ if (err)
+ goto out_class;

err = 0;
goto out;

out_class:
- i = 0;
- for_each_online_cpu(i)
- msr_device_destroy(i);
- cpu_notifier_register_done();
+ cpuhp_remove_state(CPUHP_X86_MSR_PREPARE);
class_destroy(msr_class);
out_chrdev:
__unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
@@ -265,15 +235,9 @@ static int __init msr_init(void)

static void __exit msr_exit(void)
{
- int cpu = 0;
-
- cpu_notifier_register_begin();
- for_each_online_cpu(cpu)
- msr_device_destroy(cpu);
class_destroy(msr_class);
__unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
- __unregister_hotcpu_notifier(&msr_class_cpu_notifier);
- cpu_notifier_register_done();
+ cpuhp_remove_state(CPUHP_X86_MSR_PREPARE);
}

module_init(msr_init);
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 2f9e083791c4..6506dce8343a 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -61,6 +61,7 @@ enum cpuhp_state {
CPUHP_TOPOLOGY_PREPARE,
CPUHP_X86_THERM_PREPARE,
CPUHP_X86_CPUID_PREPARE,
+ CPUHP_X86_MSR_PREPARE,
CPUHP_TIMERS_DEAD,
CPUHP_NOTF_ERR_INJ_PREPARE,
CPUHP_MIPS_SOC_PREPARE,
--
2.10.2
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