From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cong Wang Subject: [Patch net-next v3] netpoll: fix a rtnl lock assertion failure Date: Mon, 14 Jan 2013 18:43:54 +0800 Message-ID: <1358160234-24996-1-git-send-email-amwang@redhat.com> Cc: Jiri Pirko , "David S. Miller" , Cong Wang To: netdev@vger.kernel.org Return-path: Received: from mx1.redhat.com ([209.132.183.28]:42170 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756109Ab3ANKoC (ORCPT ); Mon, 14 Jan 2013 05:44:02 -0500 Sender: netdev-owner@vger.kernel.org List-ID: From: Cong Wang This patch fixes the following warning: [ 72.013864] RTNL: assertion failed at net/core/dev.c (4955) [ 72.017758] Pid: 668, comm: netpoll-prep-v6 Not tainted 3.8.0-rc1+ #474 [ 72.019582] Call Trace: [ 72.020295] [] netdev_master_upper_dev_get+0x35/0x58 [ 72.022545] [] netpoll_setup+0x61/0x340 [ 72.024846] [] store_enabled+0x82/0xc3 [ 72.027466] [] netconsole_target_attr_store+0x35/0x37 [ 72.029348] [] configfs_write_file+0xe2/0x10c [ 72.030959] [] vfs_write+0xaf/0xf6 [ 72.032359] [] ? sysret_check+0x22/0x5d [ 72.033824] [] sys_write+0x5c/0x84 [ 72.035328] [] system_call_fastpath+0x16/0x1b Just hold RCU read lock and call netdev_master_upper_dev_get_rcu(), as suggested by Jiri. Cc: Jiri Pirko Cc: David S. Miller Signed-off-by: Cong Wang --- diff --git a/net/core/netpoll.c b/net/core/netpoll.c index 9f05067..5d1f856 100644 --- a/net/core/netpoll.c +++ b/net/core/netpoll.c @@ -1055,11 +1055,14 @@ int netpoll_setup(struct netpoll *np) return -ENODEV; } - if (netdev_master_upper_dev_get(ndev)) { + rcu_read_lock(); + if (netdev_master_upper_dev_get_rcu(ndev)) { + rcu_read_unlock(); np_err(np, "%s is a slave device, aborting\n", np->dev_name); err = -EBUSY; goto put; } + rcu_read_unlock(); if (!netif_running(ndev)) { unsigned long atmost, atleast;