Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1764098AbXHQB0b (ORCPT ); Thu, 16 Aug 2007 21:26:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756279AbXHQB0X (ORCPT ); Thu, 16 Aug 2007 21:26:23 -0400 Received: from ozlabs.org ([203.10.76.45]:41023 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755789AbXHQB0V (ORCPT ); Thu, 16 Aug 2007 21:26:21 -0400 Subject: [PATCH] Only initialize hvc_console if needed, cleanup Kconfig help From: Rusty Russell To: Dave Jones Cc: Linux Kernel , Stephen Rothwell , Paul Mackerras , Benjamin Herrenschmidt , Anton Blanchard , "Ryan S. Arnold" In-Reply-To: <20070816201649.GA5375@redhat.com> References: <20070816201649.GA5375@redhat.com> Content-Type: text/plain Date: Fri, 17 Aug 2007 11:25:46 +1000 Message-Id: <1187313946.6449.68.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 Content-Length: 4496 Lines: 158 On Thu, 2007-08-16 at 16:16 -0400, Dave Jones wrote: > asides from the needed Kconfig clarification, is it necessary for khvcd > to run at all if the lguest module hasn't been loaded ? Is it possible > we can somehow delay creation of the kthread ? It's for lguest guests, so it kind of needs to be built-in. But yes, it should be made to suck less. Xen will want it too. How's this? == This changes hvc_init() to be called only when someone actually uses the hvc_console driver. 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 diff -r 0730da2377be drivers/char/Kconfig --- a/drivers/char/Kconfig Tue Aug 14 12:46:08 2007 +1000 +++ b/drivers/char/Kconfig Fri Aug 17 09:05:12 2007 +1000 @@ -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. - It will automatically be selected if one of the back-end console drivers - is selected. + Generic "hypervisor virtual console" infrastructure for various + hypervisors (pSeries, Xen, lguest). + It will automatically be selected if one of those back-end + console drivers is selected. config HVC_CONSOLE diff -r 0730da2377be drivers/char/hvc_console.c --- a/drivers/char/hvc_console.c Tue Aug 14 12:46:08 2007 +1000 +++ b/drivers/char/hvc_console.c Fri Aug 17 09:15:24 2007 +1000 @@ -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); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/