From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759438AbXIYD6j (ORCPT ); Mon, 24 Sep 2007 23:58:39 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755514AbXIYD6c (ORCPT ); Mon, 24 Sep 2007 23:58:32 -0400 Received: from ozlabs.org ([203.10.76.45]:43536 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755506AbXIYD6b (ORCPT ); Mon, 24 Sep 2007 23:58:31 -0400 Subject: [PATCH] Delay creation of khcvd thread From: Rusty Russell To: Andrew Morton , lkml - Kernel Mailing List Cc: Anton Blanchard , paulus , Benjamin Herrenschmidt , "Ryan S. Arnold" , Dave Jones Content-Type: text/plain Date: Tue, 25 Sep 2007 13:46:24 +1000 Message-Id: <1190691984.27805.270.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.10.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org This changes hvc_init() to be called only when someone actually uses the hvc_console driver. Dave Jones complained when profiling bootup. hvc_console used to only be for Power aka pSeries: now lguest and Xen both want it built-in in case the kernel is a guest under one of those, even though usually it will be a native boot. Signed-off-by: Rusty Russell --- drivers/char/Kconfig | 8 ++--- drivers/char/hvc_console.c | 66 ++++++++++++++++++++++++++++++-------------- 2 files changed, 49 insertions(+), 25 deletions(-) =================================================================== --- a/drivers/char/Kconfig +++ b/drivers/char/Kconfig @@ -568,10 +568,10 @@ config HVC_DRIVER config HVC_DRIVER bool help - Users of pSeries machines that want to utilize the hvc console front-end - module for their backend console driver should select this option. + Generic "hypervisor virtual console" infrastructure for various + hypervisors (pSeries, Xen, lguest). It will automatically be selected if one of the back-end console drivers is selected. config HVC_CONSOLE =================================================================== --- a/drivers/char/hvc_console.c +++ b/drivers/char/hvc_console.c @@ -68,6 +68,8 @@ static struct task_struct *hvc_task; /* Picks up late kicks after list walk but before schedule() */ static int hvc_kicked; + +static int hvc_init(void); #ifdef CONFIG_MAGIC_SYSRQ static int sysrq_pressed; @@ -754,6 +756,13 @@ struct hvc_struct __devinit *hvc_alloc(u struct hvc_struct *hp; int i; + /* We wait until a driver actually comes along */ + if (!hvc_driver) { + int err = hvc_init(); + if (err) + return ERR_PTR(err); + } + hp = kmalloc(ALIGN(sizeof(*hp), sizeof(long)) + outbuf_size, GFP_KERNEL); if (!hp) @@ -829,16 +838,18 @@ int __devexit hvc_remove(struct hvc_stru return 0; } -/* Driver initialization. Follow console initialization. This is where the TTY - * interfaces start to become available. */ -static int __init hvc_init(void) +/* Driver initialization: called as soon as someone uses hvc_alloc(). */ +static int hvc_init(void) { struct tty_driver *drv; + int err; /* We need more than hvc_count adapters due to hotplug additions. */ drv = alloc_tty_driver(HVC_ALLOC_TTY_ADAPTERS); - if (!drv) - return -ENOMEM; + if (!drv) { + err = -ENOMEM; + goto out; + } drv->owner = THIS_MODULE; drv->driver_name = "hvc"; @@ -854,30 +865,43 @@ static int __init hvc_init(void) * added later. */ hvc_task = kthread_run(khvcd, NULL, "khvcd"); if (IS_ERR(hvc_task)) { - panic("Couldn't create kthread for console.\n"); - put_tty_driver(drv); - return -EIO; - } - - if (tty_register_driver(drv)) - panic("Couldn't register hvc console driver\n"); - + printk(KERN_ERR "Couldn't create kthread for console.\n"); + err = PTR_ERR(hvc_task); + goto put_tty; + } + + err = tty_register_driver(drv); + if (err) { + printk(KERN_ERR "Couldn't register hvc console driver\n"); + goto stop_thread; + } + + /* FIXME: This mb() seems completely random. Remove it. */ mb(); hvc_driver = drv; return 0; -} -module_init(hvc_init); + +put_tty: + put_tty_driver(hvc_driver); +stop_thread: + kthread_stop(hvc_task); + hvc_task = NULL; +out: + return err; +} /* This isn't particularly necessary due to this being a console driver * but it is nice to be thorough. */ static void __exit hvc_exit(void) { - kthread_stop(hvc_task); - - tty_unregister_driver(hvc_driver); - /* return tty_struct instances allocated in hvc_init(). */ - put_tty_driver(hvc_driver); - unregister_console(&hvc_con_driver); + if (hvc_driver) { + kthread_stop(hvc_task); + + tty_unregister_driver(hvc_driver); + /* return tty_struct instances allocated in hvc_init(). */ + put_tty_driver(hvc_driver); + unregister_console(&hvc_con_driver); + } } module_exit(hvc_exit);