From patchwork Tue Feb 5 22:07:15 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Herton Ronaldo Krzesinski X-Patchwork-Id: 218446 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from chlorine.canonical.com (chlorine.canonical.com [91.189.94.204]) by ozlabs.org (Postfix) with ESMTP id C70C92C02BE for ; Wed, 6 Feb 2013 09:13:19 +1100 (EST) Received: from localhost ([127.0.0.1] helo=chlorine.canonical.com) by chlorine.canonical.com with esmtp (Exim 4.71) (envelope-from ) id 1U2qlI-00043h-Q9; Tue, 05 Feb 2013 22:13:08 +0000 Received: from youngberry.canonical.com ([91.189.89.112]) by chlorine.canonical.com with esmtp (Exim 4.71) (envelope-from ) id 1U2qlB-0003zg-92 for kernel-team@lists.ubuntu.com; Tue, 05 Feb 2013 22:13:02 +0000 Received: from 189.58.24.194.dynamic.adsl.gvt.net.br ([189.58.24.194] helo=canonical.com) by youngberry.canonical.com with esmtpsa (TLS1.0:DHE_RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1U2qlA-0003pX-DF; Tue, 05 Feb 2013 22:13:01 +0000 From: Herton Ronaldo Krzesinski To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Subject: [PATCH 86/93] module: wait when loading a module which is currently initializing. Date: Tue, 5 Feb 2013 20:07:15 -0200 Message-Id: <1360102042-10732-87-git-send-email-herton.krzesinski@canonical.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1360102042-10732-1-git-send-email-herton.krzesinski@canonical.com> References: <1360102042-10732-1-git-send-email-herton.krzesinski@canonical.com> X-Extended-Stable: 3.5 Cc: Rusty Russell X-BeenThere: kernel-team@lists.ubuntu.com X-Mailman-Version: 2.1.13 Precedence: list List-Id: Kernel team discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: kernel-team-bounces@lists.ubuntu.com Errors-To: kernel-team-bounces@lists.ubuntu.com 3.5.7.5 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Rusty Russell commit 9bb9c3be56834653878f766f471fa1c20e562f4c upstream. The original module-init-tools module loader used a fnctl lock on the .ko file to avoid attempts to simultaneously load a module. Unfortunately, you can't get an exclusive fcntl lock on a read-only fd, making this not work for read-only mounted filesystems. module-init-tools has a hacky sleep-and-loop for this now. It's not that hard to wait in the kernel, and only return -EEXIST once the first module has finished loading (or continue loading the module if the first one failed to initialize for some reason). It's also consistent with what we do for dependent modules which are still loading. Suggested-by: Lucas De Marchi Signed-off-by: Rusty Russell Signed-off-by: Herton Ronaldo Krzesinski --- kernel/module.c | 28 ++++++++++++++++++++++++++-- 1 file changed, 26 insertions(+), 2 deletions(-) diff --git a/kernel/module.c b/kernel/module.c index 27e302a..8dd60f4 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -2870,6 +2870,20 @@ static int post_relocation(struct module *mod, const struct load_info *info) return module_finalize(info->hdr, info->sechdrs, mod); } +/* Is this module of this name done loading? No locks held. */ +static bool finished_loading(const char *name) +{ + struct module *mod; + bool ret; + + mutex_lock(&module_mutex); + mod = find_module(name); + ret = !mod || mod->state != MODULE_STATE_COMING; + mutex_unlock(&module_mutex); + + return ret; +} + /* Allocate and load the module: note that size of section 0 is always zero, and we rely on this for optional sections. */ static struct module *load_module(void __user *umod, @@ -2877,7 +2891,7 @@ static struct module *load_module(void __user *umod, const char __user *uargs) { struct load_info info = { NULL, }; - struct module *mod; + struct module *mod, *old; long err; pr_debug("load_module: umod=%p, len=%lu, uargs=%p\n", @@ -2943,8 +2957,18 @@ static struct module *load_module(void __user *umod, * function to insert in a way safe to concurrent readers. * The mutex protects against concurrent writers. */ +again: mutex_lock(&module_mutex); - if (find_module(mod->name)) { + if ((old = find_module(mod->name)) != NULL) { + if (old->state == MODULE_STATE_COMING) { + /* Wait in case it fails to load. */ + mutex_unlock(&module_mutex); + err = wait_event_interruptible(module_wq, + finished_loading(mod->name)); + if (err) + goto free_arch_cleanup; + goto again; + } err = -EEXIST; goto unlock; }