x86/cpuid: Convert to hotplug state machine

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

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: rt@linuxtronix.de
Link: http://lkml.kernel.org/r/20161117183541.8588-3-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/arch/x86/kernel/cpuid.c b/arch/x86/kernel/cpuid.c
index 2836de390f95cdad34ff11331d9f0afd8df08998..fd85e93e069195f4716df4e8c89977a2483939c9 100644 (file)
--- a/arch/x86/kernel/cpuid.c
+++ b/arch/x86/kernel/cpuid.c
@@ -115,7 +115,7 @@ static const struct file_operations cpuid_fops = {
        .open = cpuid_open,
 };
 
-static int cpuid_device_create(int cpu)
+static int cpuid_device_create(unsigned int cpu)
 {
        struct device *dev;
 
@@ -124,35 +124,12 @@ static int cpuid_device_create(int cpu)
        return PTR_ERR_OR_ZERO(dev);
 }
 
-static void cpuid_device_destroy(int cpu)
+static int cpuid_device_destroy(unsigned int cpu)
 {
        device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu));
+       return 0;
 }
 
-static int cpuid_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 = cpuid_device_create(cpu);
-               break;
-       case CPU_UP_CANCELED:
-       case CPU_UP_CANCELED_FROZEN:
-       case CPU_DEAD:
-               cpuid_device_destroy(cpu);
-               break;
-       }
-       return notifier_from_errno(err);
-}
-
-static struct notifier_block cpuid_class_cpu_notifier =
-{
-       .notifier_call = cpuid_class_cpu_callback,
-};
-
 static char *cpuid_devnode(struct device *dev, umode_t *mode)
 {
        return kasprintf(GFP_KERNEL, "cpu/%u/cpuid", MINOR(dev->devt));
@@ -160,15 +137,13 @@ static char *cpuid_devnode(struct device *dev, umode_t *mode)
 
 static int __init cpuid_init(void)
 {
-       int i, err = 0;
-       i = 0;
+       int err;
 
        if (__register_chrdev(CPUID_MAJOR, 0, NR_CPUS,
                              "cpu/cpuid", &cpuid_fops)) {
                printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n",
                       CPUID_MAJOR);
-               err = -EBUSY;
-               goto out;
+               return -EBUSY;
        }
        cpuid_class = class_create(THIS_MODULE, "cpuid");
        if (IS_ERR(cpuid_class)) {
@@ -177,42 +152,25 @@ static int __init cpuid_init(void)
        }
        cpuid_class->devnode = cpuid_devnode;
 
-       cpu_notifier_register_begin();
-       for_each_online_cpu(i) {
-               err = cpuid_device_create(i);
-               if (err != 0)
-                       goto out_class;
-       }
-       __register_hotcpu_notifier(&cpuid_class_cpu_notifier);
-       cpu_notifier_register_done();
+       err = cpuhp_setup_state(CPUHP_X86_CPUID_PREPARE, "x86/cpuid:prepare",
+                               cpuid_device_create, cpuid_device_destroy);
+       if (err)
+               goto out_class;
 
-       err = 0;
-       goto out;
+       return 0;
 
 out_class:
-       i = 0;
-       for_each_online_cpu(i) {
-               cpuid_device_destroy(i);
-       }
-       cpu_notifier_register_done();
        class_destroy(cpuid_class);
 out_chrdev:
        __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
-out:
        return err;
 }
 
 static void __exit cpuid_exit(void)
 {
-       int cpu = 0;
-
-       cpu_notifier_register_begin();
-       for_each_online_cpu(cpu)
-               cpuid_device_destroy(cpu);
+       cpuhp_remove_state(CPUHP_X86_CPUID_PREPARE);
        class_destroy(cpuid_class);
        __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
-       __unregister_hotcpu_notifier(&cpuid_class_cpu_notifier);
-       cpu_notifier_register_done();
 }
 
 module_init(cpuid_init);

diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 79b96f647d643e1c715e90cd69d1160cd2f40452..bc340ef2f2009b23acb69414a1113b0b46d5083c 100644 (file)
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -59,6 +59,7 @@ enum cpuhp_state {
        CPUHP_BLK_MQ_PREPARE,
        CPUHP_NET_FLOW_PREPARE,
        CPUHP_TOPOLOGY_PREPARE,
+       CPUHP_X86_CPUID_PREPARE,
        CPUHP_TIMERS_DEAD,
        CPUHP_NOTF_ERR_INJ_PREPARE,
        CPUHP_MIPS_SOC_PREPARE,