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Subject[tip:smp/hotplug] x86/msr: Convert to hotplug state machine
Commit-ID:  8fba38c937cd585bcf562fda8db3decb25509506
Gitweb: http://git.kernel.org/tip/8fba38c937cd585bcf562fda8db3decb25509506
Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
AuthorDate: Thu, 17 Nov 2016 19:35:24 +0100
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Tue, 22 Nov 2016 23:34:39 +0100

x86/msr: Convert to hotplug state machine

Install the callbacks via the state machine and let the core invoke
the callbacks on the already online CPUs.

Move the callbacks to online/offline as there is no point in having the
files around before the cpu is online and until its completely gone.

[ tglx: Move the callbacks to online/offline ]

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: rt@linuxtronix.de
Link: http://lkml.kernel.org/r/20161117183541.8588-4-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
arch/x86/kernel/msr.c | 69 +++++++++++----------------------------------------
1 file changed, 15 insertions(+), 54 deletions(-)

diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c
index 7f3550a..f5e3ff8 100644
--- a/arch/x86/kernel/msr.c
+++ b/arch/x86/kernel/msr.c
@@ -44,6 +44,7 @@
#include <asm/msr.h>

static struct class *msr_class;
+static enum cpuhp_state cpuhp_msr_state;

static ssize_t msr_read(struct file *file, char __user *buf,
size_t count, loff_t *ppos)
@@ -180,7 +181,7 @@ 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 +190,12 @@ 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));
@@ -224,13 +203,11 @@ 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);
- err = -EBUSY;
- goto out;
+ return -EBUSY;
}
msr_class = class_create(THIS_MODULE, "msr");
if (IS_ERR(msr_class)) {
@@ -239,44 +216,28 @@ 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 = 0;
- goto out;
+ err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/msr:online",
+ msr_device_create, msr_device_destroy);
+ if (err < 0)
+ goto out_class;
+ cpuhp_msr_state = err;
+ return 0;

out_class:
- i = 0;
- for_each_online_cpu(i)
- msr_device_destroy(i);
- cpu_notifier_register_done();
+ cpuhp_remove_state(cpuhp_msr_state);
class_destroy(msr_class);
out_chrdev:
__unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
-out:
return err;
}
+module_init(msr_init);

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

MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
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