Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934890AbcKMLgv (ORCPT ); Sun, 13 Nov 2016 06:36:51 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:35892 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933991AbcKMLZd (ORCPT ); Sun, 13 Nov 2016 06:25:33 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, John Sperbeck , Eric Dumazet , Jesper Dangaard Brouer , "David S. Miller" Subject: [PATCH 4.4 17/34] net: pktgen: remove rcu locking in pktgen_change_name() Date: Sun, 13 Nov 2016 12:24:49 +0100 Message-Id: <20161113112400.826080973@linuxfoundation.org> X-Mailer: git-send-email 2.10.2 In-Reply-To: <20161113112400.008903838@linuxfoundation.org> References: <20161113112400.008903838@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2834 Lines: 91 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit 9a0b1e8ba4061778897b544afc898de2163382f7 ] After Jesper commit back in linux-3.18, we trigger a lockdep splat in proc_create_data() while allocating memory from pktgen_change_name(). This patch converts t->if_lock to a mutex, since it is now only used from control path, and adds proper locking to pktgen_change_name() 1) pktgen_thread_lock to protect the outer loop (iterating threads) 2) t->if_lock to protect the inner loop (iterating devices) Note that before Jesper patch, pktgen_change_name() was lacking proper protection, but lockdep was not able to detect the problem. Fixes: 8788370a1d4b ("pktgen: RCU-ify "if_list" to remove lock in next_to_run()") Reported-by: John Sperbeck Signed-off-by: Eric Dumazet Cc: Jesper Dangaard Brouer Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/core/pktgen.c | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) --- a/net/core/pktgen.c +++ b/net/core/pktgen.c @@ -215,8 +215,8 @@ #define M_NETIF_RECEIVE 1 /* Inject packets into stack */ /* If lock -- protects updating of if_list */ -#define if_lock(t) spin_lock(&(t->if_lock)); -#define if_unlock(t) spin_unlock(&(t->if_lock)); +#define if_lock(t) mutex_lock(&(t->if_lock)); +#define if_unlock(t) mutex_unlock(&(t->if_lock)); /* Used to help with determining the pkts on receive */ #define PKTGEN_MAGIC 0xbe9be955 @@ -422,7 +422,7 @@ struct pktgen_net { }; struct pktgen_thread { - spinlock_t if_lock; /* for list of devices */ + struct mutex if_lock; /* for list of devices */ struct list_head if_list; /* All device here */ struct list_head th_list; struct task_struct *tsk; @@ -2002,11 +2002,13 @@ static void pktgen_change_name(const str { struct pktgen_thread *t; + mutex_lock(&pktgen_thread_lock); + list_for_each_entry(t, &pn->pktgen_threads, th_list) { struct pktgen_dev *pkt_dev; - rcu_read_lock(); - list_for_each_entry_rcu(pkt_dev, &t->if_list, list) { + if_lock(t); + list_for_each_entry(pkt_dev, &t->if_list, list) { if (pkt_dev->odev != dev) continue; @@ -2021,8 +2023,9 @@ static void pktgen_change_name(const str dev->name); break; } - rcu_read_unlock(); + if_unlock(t); } + mutex_unlock(&pktgen_thread_lock); } static int pktgen_device_event(struct notifier_block *unused, @@ -3726,7 +3729,7 @@ static int __net_init pktgen_create_thre return -ENOMEM; } - spin_lock_init(&t->if_lock); + mutex_init(&t->if_lock); t->cpu = cpu; INIT_LIST_HEAD(&t->if_list);