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SubjectRe: [PATCH 12/20] net/iucv: Convert to hotplug state machine
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Sebastian,

your patch looks good to me. I run successfully some small tests with it.
I want to suggest a small change in iucv_init() to keep the uniform technique
of undo labels below. Do you agree?

Kind regards, Ursula

On 11/17/2016 07:35 PM, Sebastian Andrzej Siewior wrote:
> Install the callbacks via the state machine and let the core invoke the
> callbacks on the already online CPUs. The smp function calls in the
> online/downprep callbacks are not required as the callback is guaranteed to
> be invoked on the upcoming/outgoing cpu.
>
> Cc: Ursula Braun <ubraun@linux.vnet.ibm.com>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: linux-s390@vger.kernel.org
> Cc: netdev@vger.kernel.org
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
> include/linux/cpuhotplug.h | 1 +
> net/iucv/iucv.c | 118 +++++++++++++++++----------------------------
> 2 files changed, 45 insertions(+), 74 deletions(-)
>
> diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
> index fd5598b8353a..69abf2c09f6c 100644
> --- a/include/linux/cpuhotplug.h
> +++ b/include/linux/cpuhotplug.h
> @@ -63,6 +63,7 @@ enum cpuhp_state {
> CPUHP_X86_THERM_PREPARE,
> CPUHP_X86_CPUID_PREPARE,
> CPUHP_X86_MSR_PREPARE,
> + CPUHP_NET_IUCV_PREPARE,
> CPUHP_TIMERS_DEAD,
> CPUHP_NOTF_ERR_INJ_PREPARE,
> CPUHP_MIPS_SOC_PREPARE,
> diff --git a/net/iucv/iucv.c b/net/iucv/iucv.c
> index 88a2a3ba4212..f0d6afc5d4a9 100644
> --- a/net/iucv/iucv.c
> +++ b/net/iucv/iucv.c
> @@ -639,7 +639,7 @@ static void iucv_disable(void)
> put_online_cpus();
> }
>
> -static void free_iucv_data(int cpu)
> +static int iucv_cpu_dead(unsigned int cpu)
> {
> kfree(iucv_param_irq[cpu]);
> iucv_param_irq[cpu] = NULL;
> @@ -647,9 +647,10 @@ static void free_iucv_data(int cpu)
> iucv_param[cpu] = NULL;
> kfree(iucv_irq_data[cpu]);
> iucv_irq_data[cpu] = NULL;
> + return 0;
> }
>
> -static int alloc_iucv_data(int cpu)
> +static int iucv_cpu_prepare(unsigned int cpu)
> {
> /* Note: GFP_DMA used to get memory below 2G */
> iucv_irq_data[cpu] = kmalloc_node(sizeof(struct iucv_irq_data),
> @@ -671,58 +672,38 @@ static int alloc_iucv_data(int cpu)
> return 0;
>
> out_free:
> - free_iucv_data(cpu);
> + iucv_cpu_dead(cpu);
> return -ENOMEM;
> }
>
> -static int iucv_cpu_notify(struct notifier_block *self,
> - unsigned long action, void *hcpu)
> +static int iucv_cpu_online(unsigned int cpu)
> {
> - cpumask_t cpumask;
> - long cpu = (long) hcpu;
> -
> - switch (action) {
> - case CPU_UP_PREPARE:
> - case CPU_UP_PREPARE_FROZEN:
> - if (alloc_iucv_data(cpu))
> - return notifier_from_errno(-ENOMEM);
> - break;
> - case CPU_UP_CANCELED:
> - case CPU_UP_CANCELED_FROZEN:
> - case CPU_DEAD:
> - case CPU_DEAD_FROZEN:
> - free_iucv_data(cpu);
> - break;
> - case CPU_ONLINE:
> - case CPU_ONLINE_FROZEN:
> - case CPU_DOWN_FAILED:
> - case CPU_DOWN_FAILED_FROZEN:
> - if (!iucv_path_table)
> - break;
> - smp_call_function_single(cpu, iucv_declare_cpu, NULL, 1);
> - break;
> - case CPU_DOWN_PREPARE:
> - case CPU_DOWN_PREPARE_FROZEN:
> - if (!iucv_path_table)
> - break;
> - cpumask_copy(&cpumask, &iucv_buffer_cpumask);
> - cpumask_clear_cpu(cpu, &cpumask);
> - if (cpumask_empty(&cpumask))
> - /* Can't offline last IUCV enabled cpu. */
> - return notifier_from_errno(-EINVAL);
> - smp_call_function_single(cpu, iucv_retrieve_cpu, NULL, 1);
> - if (cpumask_empty(&iucv_irq_cpumask))
> - smp_call_function_single(
> - cpumask_first(&iucv_buffer_cpumask),
> - iucv_allow_cpu, NULL, 1);
> - break;
> - }
> - return NOTIFY_OK;
> + if (!iucv_path_table)
> + return 0;
> + iucv_declare_cpu(NULL);
> + return 0;
> }
>
> -static struct notifier_block __refdata iucv_cpu_notifier = {
> - .notifier_call = iucv_cpu_notify,
> -};
> +static int iucv_cpu_down_prep(unsigned int cpu)
> +{
> + cpumask_t cpumask;
> +
> + if (!iucv_path_table)
> + return 0;
> +
> + cpumask_copy(&cpumask, &iucv_buffer_cpumask);
> + cpumask_clear_cpu(cpu, &cpumask);
> + if (cpumask_empty(&cpumask))
> + /* Can't offline last IUCV enabled cpu. */
> + return -EINVAL;
> +
> + iucv_retrieve_cpu(NULL);
> + if (!cpumask_empty(&iucv_irq_cpumask))
> + return 0;
> + smp_call_function_single(cpumask_first(&iucv_buffer_cpumask),
> + iucv_allow_cpu, NULL, 1);
> + return 0;
> +}
>
> /**
> * iucv_sever_pathid
> @@ -2027,6 +2008,7 @@ struct iucv_interface iucv_if = {
> };
> EXPORT_SYMBOL(iucv_if);
>
> +static enum cpuhp_state iucv_online;
> /**
> * iucv_init
> *
> @@ -2035,7 +2017,6 @@ EXPORT_SYMBOL(iucv_if);
> static int __init iucv_init(void)
> {
> int rc;
> - int cpu;
>
> if (!MACHINE_IS_VM) {
> rc = -EPROTONOSUPPORT;
> @@ -2054,23 +2035,19 @@ static int __init iucv_init(void)
> goto out_int;
> }
>
> - cpu_notifier_register_begin();
> -
> - for_each_online_cpu(cpu) {
> - if (alloc_iucv_data(cpu)) {
> - rc = -ENOMEM;
> - goto out_free;
> - }
> - }
> - rc = __register_hotcpu_notifier(&iucv_cpu_notifier);
> + rc = cpuhp_setup_state(CPUHP_NET_IUCV_PREPARE, "net/iucv:prepare",
> + iucv_cpu_prepare, iucv_cpu_dead);
> if (rc)
> goto out_free;
> -
> - cpu_notifier_register_done();
> + rc = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "net/iucv:online",
> + iucv_cpu_online, iucv_cpu_down_prep);
> + if (rc < 0)
> + goto out_free;
> + iucv_online = rc;
>
> rc = register_reboot_notifier(&iucv_reboot_notifier);
> if (rc)
> - goto out_cpu;
> + goto out_free;
> ASCEBC(iucv_error_no_listener, 16);
> ASCEBC(iucv_error_no_memory, 16);
> ASCEBC(iucv_error_pathid, 16);
> @@ -2084,14 +2061,10 @@ static int __init iucv_init(void)
>
> out_reboot:
> unregister_reboot_notifier(&iucv_reboot_notifier);
> -out_cpu:
> - cpu_notifier_register_begin();
> - __unregister_hotcpu_notifier(&iucv_cpu_notifier);
> out_free:
> - for_each_possible_cpu(cpu)
> - free_iucv_data(cpu);
> -
> - cpu_notifier_register_done();
> + if (iucv_online)
> + cpuhp_remove_state(iucv_online);
> + cpuhp_remove_state(CPUHP_NET_IUCV_PREPARE);
>
> root_device_unregister(iucv_root);
> out_int:
I prefer to keep the technique of cascaded undo labels here, like this:
@@ -2054,23 +2035,19 @@ static int __init iucv_init(void)
goto out_int;
}

- cpu_notifier_register_begin();
-
- for_each_online_cpu(cpu) {
- if (alloc_iucv_data(cpu)) {
- rc = -ENOMEM;
- goto out_free;
- }
- }
- rc = __register_hotcpu_notifier(&iucv_cpu_notifier);
+ rc = cpuhp_setup_state(CPUHP_NET_IUCV_PREPARE, "net/iucv:prepare",
+ iucv_cpu_prepare, iucv_cpu_dead);
if (rc)
- goto out_free;
-
- cpu_notifier_register_done();
+ goto out_dev;
+ rc = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "net/iucv:online",
+ iucv_cpu_online, iucv_cpu_down_prep);
+ if (rc < 0)
+ goto out_prep;
+ iucv_online = rc;

rc = register_reboot_notifier(&iucv_reboot_notifier);
if (rc)
- goto out_cpu;
+ goto out_remove;
ASCEBC(iucv_error_no_listener, 16);
ASCEBC(iucv_error_no_memory, 16);
ASCEBC(iucv_error_pathid, 16);
@@ -2084,15 +2061,12 @@ static int __init iucv_init(void)

out_reboot:
unregister_reboot_notifier(&iucv_reboot_notifier);
-out_cpu:
- cpu_notifier_register_begin();
- __unregister_hotcpu_notifier(&iucv_cpu_notifier);
-out_free:
- for_each_possible_cpu(cpu)
- free_iucv_data(cpu);
-
- cpu_notifier_register_done();
-
+out_remove:
+ if (iucv_online)
+ cpuhp_remove_state(iucv_online);
+out_prep:
+ cpuhp_remove_state(CPUHP_NET_IUCV_PREPARE);
+out_dev:
root_device_unregister(iucv_root);
out_int:
unregister_external_irq(EXT_IRQ_IUCV, iucv_external_interrupt);
> @@ -2110,7 +2083,6 @@ static int __init iucv_init(void)
> static void __exit iucv_exit(void)
> {
> struct iucv_irq_list *p, *n;
> - int cpu;
>
> spin_lock_irq(&iucv_queue_lock);
> list_for_each_entry_safe(p, n, &iucv_task_queue, list)
> @@ -2119,11 +2091,9 @@ static void __exit iucv_exit(void)
> kfree(p);
> spin_unlock_irq(&iucv_queue_lock);
> unregister_reboot_notifier(&iucv_reboot_notifier);
> - cpu_notifier_register_begin();
> - __unregister_hotcpu_notifier(&iucv_cpu_notifier);
> - for_each_possible_cpu(cpu)
> - free_iucv_data(cpu);
> - cpu_notifier_register_done();
> +
> + cpuhp_remove_state_nocalls(iucv_online);
> + cpuhp_remove_state(CPUHP_NET_IUCV_PREPARE);
> root_device_unregister(iucv_root);
> bus_unregister(&iucv_bus);
> unregister_external_irq(EXT_IRQ_IUCV, iucv_external_interrupt);
>

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