Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754657AbbDPXHJ (ORCPT ); Thu, 16 Apr 2015 19:07:09 -0400 Received: from mail-qc0-f178.google.com ([209.85.216.178]:35851 "EHLO mail-qc0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753865AbbDPXEf (ORCPT ); Thu, 16 Apr 2015 19:04:35 -0400 From: Tejun Heo To: akpm@linux-foundation.org, davem@davemloft.net Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org, Tejun Heo Subject: [PATCH 10/16] netconsole: introduce netconsole_mutex Date: Thu, 16 Apr 2015 19:03:47 -0400 Message-Id: <1429225433-11946-11-git-send-email-tj@kernel.org> X-Mailer: git-send-email 2.1.0 In-Reply-To: <1429225433-11946-1-git-send-email-tj@kernel.org> References: <1429225433-11946-1-git-send-email-tj@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6198 Lines: 197 console_lock protects the target_list itself and setting and clearing of its ->enabled flag; however, nothing protects the overall enable/disable operations which we'll need to make netconsole management more dynamic for the scheduled reliable transmission support. Also, an earlier patch introduced a small race window where dynamic console disable may compete against asynchronous disable kicked off from netdevice_notifier. This patch adds netconsole_mutex which protects all target create/destroy and enable/disable operations. It also replaces netconsole_target->mutex used by dynamic consoles. The above mentioned race is removed by this change. Signed-off-by: Tejun Heo Cc: David Miller --- drivers/net/netconsole.c | 48 ++++++++++++++++++++++++++++-------------------- 1 file changed, 28 insertions(+), 20 deletions(-) diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c index 57c02ab..f0ac9f6 100644 --- a/drivers/net/netconsole.c +++ b/drivers/net/netconsole.c @@ -75,10 +75,14 @@ __setup("netconsole=", option_setup); /* * Linked list of all configured targets. The list and each target's - * enable/disable state are protected by console_lock. + * enable/disable state are protected by both netconsole_mutex and + * console_lock. */ static LIST_HEAD(target_list); +/* protects target creation/destruction and enable/disable */ +static DEFINE_MUTEX(netconsole_mutex); + /** * struct netconsole_target - Represents a configured netconsole target. * @list: Links this target into the target_list. @@ -106,7 +110,6 @@ struct netconsole_target { #endif bool enabled; bool disable_scheduled; - struct mutex mutex; struct netpoll np; }; @@ -184,7 +187,6 @@ static struct netconsole_target *alloc_netconsole_target(void) strlcpy(nt->np.dev_name, "eth0", IFNAMSIZ); nt->np.local_port = 6665; nt->np.remote_port = 6666; - mutex_init(&nt->mutex); eth_broadcast_addr(nt->np.remote_mac); return nt; @@ -196,6 +198,8 @@ static struct netconsole_target *alloc_param_target(char *target_config) int err = -ENOMEM; struct netconsole_target *nt; + lockdep_assert_held(&netconsole_mutex); + nt = alloc_netconsole_target(); if (!nt) goto fail; @@ -573,10 +577,10 @@ static ssize_t netconsole_target_attr_store(struct config_item *item, struct netconsole_target_attr *na = container_of(attr, struct netconsole_target_attr, attr); - mutex_lock(&nt->mutex); + mutex_lock(&netconsole_mutex); if (na->store) ret = na->store(nt, buf, count); - mutex_unlock(&nt->mutex); + mutex_unlock(&netconsole_mutex); return ret; } @@ -610,9 +614,11 @@ static struct config_item *make_netconsole_target(struct config_group *group, config_item_init_type_name(&nt->item, name, &netconsole_target_type); /* Adding, but it is disabled */ + mutex_lock(&netconsole_mutex); console_lock(); list_add(&nt->list, &target_list); console_unlock(); + mutex_unlock(&netconsole_mutex); return &nt->item; } @@ -622,6 +628,7 @@ static void drop_netconsole_target(struct config_group *group, { struct netconsole_target *nt = to_target(item); + mutex_lock(&netconsole_mutex); console_lock(); list_del(&nt->list); console_unlock(); @@ -634,6 +641,7 @@ static void drop_netconsole_target(struct config_group *group, netpoll_cleanup(&nt->np); config_item_put(&nt->item); + mutex_unlock(&netconsole_mutex); } static struct configfs_group_operations netconsole_subsys_group_ops = { @@ -662,6 +670,7 @@ static void netconsole_deferred_disable_work_fn(struct work_struct *work) { struct netconsole_target *nt, *to_disable; + mutex_lock(&netconsole_mutex); repeat: to_disable = NULL; console_lock(); @@ -685,6 +694,8 @@ repeat: netconsole_target_put(to_disable); goto repeat; } + + mutex_unlock(&netconsole_mutex); } static DECLARE_WORK(netconsole_deferred_disable_work, @@ -791,6 +802,8 @@ static int __init init_netconsole(void) char *target_config; char *input = config; + mutex_lock(&netconsole_mutex); + if (strnlen(input, MAX_PARAM_LENGTH)) { while ((target_config = strsep(&input, ";"))) { nt = alloc_param_target(target_config); @@ -818,24 +831,21 @@ static int __init init_netconsole(void) register_console(&netconsole); pr_info("network logging started\n"); + mutex_unlock(&netconsole_mutex); return err; undonotifier: unregister_netdevice_notifier(&netconsole_netdev_notifier); - cancel_work_sync(&netconsole_deferred_disable_work); fail: pr_err("cleaning up\n"); - /* - * Remove all targets and destroy them (only targets created - * from the boot/module option exist here). Skipping the console - * lock is safe here. - */ + /* targets are already inactive, skipping the console lock is safe */ list_for_each_entry_safe(nt, tmp, &target_list, list) { list_del(&nt->list); free_param_target(nt); } - + mutex_unlock(&netconsole_mutex); + cancel_work_sync(&netconsole_deferred_disable_work); return err; } @@ -843,22 +853,20 @@ static void __exit cleanup_netconsole(void) { struct netconsole_target *nt, *tmp; + mutex_lock(&netconsole_mutex); + unregister_console(&netconsole); dynamic_netconsole_exit(); unregister_netdevice_notifier(&netconsole_netdev_notifier); - cancel_work_sync(&netconsole_deferred_disable_work); - /* - * Targets created via configfs pin references on our module - * and would first be rmdir(2)'ed from userspace. We reach - * here only when they are already destroyed, and only those - * created from the boot/module option are left, so remove and - * destroy them. Skipping the console lock is safe here. - */ + /* targets are already inactive, skipping the console lock is safe */ list_for_each_entry_safe(nt, tmp, &target_list, list) { list_del(&nt->list); free_param_target(nt); } + + mutex_unlock(&netconsole_mutex); + cancel_work_sync(&netconsole_deferred_disable_work); } /* -- 2.1.0 -- 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/