From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754395AbcJUGXd (ORCPT ); Fri, 21 Oct 2016 02:23:33 -0400 Received: from mail-pf0-f194.google.com ([209.85.192.194]:35296 "EHLO mail-pf0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753897AbcJUGXc (ORCPT ); Fri, 21 Oct 2016 02:23:32 -0400 Date: Fri, 21 Oct 2016 15:23:27 +0900 From: Sergey Senozhatsky To: Minchan Kim Cc: Andrew Morton , Sergey Senozhatsky , linux-kernel@vger.kernel.org Subject: Re: [PATCH 3/3] zram: adjust the number of zram thread Message-ID: <20161021062327.GC527@swordfish> References: <1474526565-6676-1-git-send-email-minchan@kernel.org> <1474526565-6676-3-git-send-email-minchan@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1474526565-6676-3-git-send-email-minchan@kernel.org> User-Agent: Mutt/1.7.1 (2016-10-04) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 >