From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753836AbZBHSwg (ORCPT ); Sun, 8 Feb 2009 13:52:36 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753099AbZBHSw2 (ORCPT ); Sun, 8 Feb 2009 13:52:28 -0500 Received: from casper.infradead.org ([85.118.1.10]:53611 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752557AbZBHSw1 convert rfc822-to-8bit (ORCPT ); Sun, 8 Feb 2009 13:52:27 -0500 Date: Sun, 8 Feb 2009 10:42:01 -0800 From: Arjan van de Ven To: linux-kernel@vger.kernel.org Cc: rusty@rustcorp.com.au, jkosina@suse.cz, mchehab@infradead.org Subject: [PATCH 1/3] module: create a request_module_nowait() Message-ID: <20090208104201.6124ab6a@infradead.org> Organization: Intel X-Mailer: Claws Mail 3.7.0 (GTK+ 2.14.7; i386-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>From 48cd2d5171ae8fb40ef6092a566b4889b9ac72b7 Mon Sep 17 00:00:00 2001 From: Arjan van de Ven Date: Sun, 1 Feb 2009 12:02:39 -0800 Subject: [PATCH] module: create a request_module_nowait() There seems to be a common pattern in the kernel where drivers want to call request_module() from inside a module_init() function. Currently this would deadlock. As a result, several drivers go through hoops like scheduling things via kevent, or creating custom work queues (because kevent can deadlock on them). This patch changes this to use a request_module_nowait() function macro instead, which just fires the modprobe off but doesn't wait for it, and thus avoids the original deadlock entirely. On my laptop this already results in one less kernel thread running.. Signed-off-by: Arjan van de Ven --- include/linux/kmod.h | 9 ++++++--- kernel/kmod.c | 10 ++++++---- 2 files changed, 12 insertions(+), 7 deletions(-) diff --git a/include/linux/kmod.h b/include/linux/kmod.h index 92213a9..73b2b56 100644 --- a/include/linux/kmod.h +++ b/include/linux/kmod.h @@ -29,10 +29,13 @@ #ifdef CONFIG_MODULES /* modprobe exit status on success, -ve on error. Return value * usually useless though. */ -extern int request_module(const char * name, ...) __attribute__ ((format (printf, 1, 2))); -#define try_then_request_module(x, mod...) ((x) ?: (request_module(mod), (x))) +extern int __request_module(int wait, const char *name, ...) __attribute__ ((format (printf, 2, 3))); +#define request_module(mod...) __request_module(1, mod) +#define request_module_nowait(mod...) __request_module(0, mod) +#define try_then_request_module(x, mod...) ((x) ?: (__request_module(0, mod), (x))) #else -static inline int request_module(const char * name, ...) { return -ENOSYS; } +static inline int request_module(const char *name, ...) { return -ENOSYS; } +static inline int request_module_nowait(const char *name, ...) { return -ENOSYS; } #define try_then_request_module(x, mod...) (x) #endif diff --git a/kernel/kmod.c b/kernel/kmod.c index a27a5f6..3b90ea5 100644 --- a/kernel/kmod.c +++ b/kernel/kmod.c @@ -50,7 +50,8 @@ static struct workqueue_struct *khelper_wq; char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe"; /** - * request_module - try to load a kernel module + * __request_module - try to load a kernel module + * @wait: wait (or not) for the operation to complete * @fmt: printf style format string for the name of the module * @...: arguments as specified in the format string * @@ -63,7 +64,8 @@ char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe"; * If module auto-loading support is disabled then this function * becomes a no-operation. */ -int request_module(const char *fmt, ...) + +int __request_module(int wait, const char *fmt, ...) { va_list args; char module_name[MODULE_NAME_LEN]; @@ -108,11 +110,11 @@ int request_module(const char *fmt, ...) return -ENOMEM; } - ret = call_usermodehelper(modprobe_path, argv, envp, 1); + ret = call_usermodehelper(modprobe_path, argv, envp, wait); atomic_dec(&kmod_concurrent); return ret; } -EXPORT_SYMBOL(request_module); +EXPORT_SYMBOL(__request_module); #endif /* CONFIG_MODULES */ struct subprocess_info { -- 1.6.0.6 -- Arjan van de Ven Intel Open Source Technology Centre For development, discussion and tips for power savings, visit http://www.lesswatts.org