On (09/22/16 15:42), Minchan Kim wrote:
[..]
> +static int __zram_cpu_notifier(void *dummy, unsigned long action,
> + unsigned long cpu)
> {
> struct zram_worker *worker;
>
> - while (!list_empty(&workers.worker_list)) {
> + switch (action) {
> + case CPU_UP_PREPARE:
> + worker = kmalloc(sizeof(*worker), GFP_KERNEL);
> + if (!worker) {
> + pr_err("Can't allocate a worker\n");
> + return NOTIFY_BAD;
> + }
> +
> + worker->task = kthread_run(zram_thread, NULL, "zramd-%lu", cpu);
> + if (IS_ERR(worker->task)) {
> + kfree(worker);
> + pr_err("Can't allocate a zram thread\n");
> + return NOTIFY_BAD;
> + }
well, strictly speaking we are have no strict bound-to-cpu (per-cpu)
requirement here, we just want to have num_online_cpus() worker threads.
if we fail to create one more worker thread nothing really bad happens,
so I think we better not block that cpu from coming online.
iow, always 'return NOTIFY_OK'.
-ss
> + spin_lock(&workers.req_lock);
> + list_add(&worker->list, &workers.worker_list);
> + spin_unlock(&workers.req_lock);
> + break;
> + case CPU_DEAD:
> + case CPU_UP_CANCELED:
> + spin_lock(&workers.req_lock);
> + WARN_ON(list_empty(&workers.worker_list));
> +
> worker = list_first_entry(&workers.worker_list,
> - struct zram_worker,
> - list);
> - kthread_stop(worker->task);
> + struct zram_worker, list);
> list_del(&worker->list);
> + spin_unlock(&workers.req_lock);
> +
> + kthread_stop(worker->task);
> kfree(worker);
> + break;
> + default:
> + break;
> }
> + return NOTIFY_OK;
> +}
> +
> +static int zram_cpu_notifier(struct notifier_block *nb,
> + unsigned long action, void *pcpu)
> +{
> + unsigned long cpu = (unsigned long)pcpu;
> +
> + return __zram_cpu_notifier(NULL, action, cpu);
> +}
> +
> +static void destroy_workers(void)
> +{
> + unsigned long cpu;
> +
> + cpu_notifier_register_begin();
> + for_each_online_cpu(cpu)
> + __zram_cpu_notifier(NULL, CPU_UP_CANCELED, cpu);
> + __unregister_cpu_notifier(&workers.notifier);
> + cpu_notifier_register_done();
>
> WARN_ON(workers.nr_running);
> }
>
> static int create_workers(void)
> {
> - int i;
> - int nr_cpu = num_online_cpus();
> - struct zram_worker *worker;
> + int cpu;
>
> INIT_LIST_HEAD(&workers.worker_list);
> INIT_LIST_HEAD(&workers.req_list);
> spin_lock_init(&workers.req_lock);
> init_waitqueue_head(&workers.req_wait);
>
> - for (i = 0; i < nr_cpu; i++) {
> - worker = kmalloc(sizeof(*worker), GFP_KERNEL);
> - if (!worker)
> - goto error;
> -
> - worker->task = kthread_run(zram_thread, NULL, "zramd-%d", i);
> - if (IS_ERR(worker->task)) {
> - kfree(worker);
> - goto error;
> - }
> -
> - list_add(&worker->list, &workers.worker_list);
> + workers.notifier.notifier_call = zram_cpu_notifier;
> + cpu_notifier_register_begin();
> + for_each_online_cpu(cpu) {
> + if (__zram_cpu_notifier(NULL, CPU_UP_PREPARE, cpu) ==
> + NOTIFY_BAD)
> + goto cleanup;
> }
>
> + __register_cpu_notifier(&workers.notifier);
> + cpu_notifier_register_done();
> +
> return 0;
> +cleanup:
> + for_each_online_cpu(cpu)
> + __zram_cpu_notifier(NULL, CPU_UP_CANCELED, cpu);
> + cpu_notifier_register_done();
>
> -error:
> - destroy_workers();
> - return 1;
> + return -ENOMEM;
> }
>
> static int zram_rw_async_page(struct zram *zram,
> --
> 2.7.4
>
