Return-path: Received: from perninha.conectiva.com.br ([200.140.247.100]:35423 "EHLO perninha.conectiva.com.br" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751753AbZHZQyN (ORCPT ); Wed, 26 Aug 2009 12:54:13 -0400 From: Herton Ronaldo Krzesinski To: linux-wireless@vger.kernel.org Cc: John W Linville , Larry Finger , Hin-Tak Leung , Herton Ronaldo Krzesinski Subject: [PATCH 1/2] rtl8187: fix circular locking (rtl8187_stop/rtl8187_work) Date: Wed, 26 Aug 2009 13:54:08 -0300 Message-Id: <1251305649-12508-1-git-send-email-herton@mandriva.com.br> Sender: linux-wireless-owner@vger.kernel.org List-ID: Larry Finger reports following lockdep warning: [ INFO: possible circular locking dependency detected ] 2.6.31-rc6-wl #201 ------------------------------------------------------- rfkill/30578 is trying to acquire lock: (&(&priv->work)->work#2){+.+...}, at: [] __cancel_work_timer+0xd9/0x222 but task is already holding lock: (&priv->conf_mutex#2){+.+.+.}, at: [] rtl8187_stop+0x31/0x364 [rtl8187] which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&priv->conf_mutex#2){+.+.+.}: [] __lock_acquire+0x12d0/0x1614 [] lock_acquire+0xb9/0xdd [] mutex_lock_nested+0x56/0x2a8 [] rtl8187_work+0x3b/0xf2 [rtl8187] [] worker_thread+0x1fa/0x30a [] kthread+0x8f/0x97 [] child_rip+0xa/0x20 [] 0xffffffffffffffff -> #0 (&(&priv->work)->work#2){+.+...}: [] __lock_acquire+0x1005/0x1614 [] lock_acquire+0xb9/0xdd [] __cancel_work_timer+0x112/0x222 [] cancel_delayed_work_sync+0xd/0xf [] rtl8187_stop+0x34c/0x364 [rtl8187] [] ieee80211_stop_device+0x29/0x61 [mac80211] [] ieee80211_stop+0x476/0x530 [mac80211] [] dev_close+0x8a/0xac [] cfg80211_rfkill_set_block+0x4a/0x7a [cfg80211] [] rfkill_set_block+0x84/0xd9 [rfkill] [] rfkill_fop_write+0xda/0x124 [rfkill] [] vfs_write+0xae/0x14a [] sys_write+0x47/0x6e [] system_call_fastpath+0x16/0x1b [] 0xffffffffffffffff The problem here is that rtl8187_stop, while helding priv->conf_mutex, runs cancel_delayed_work_sync on an workqueue that runs rtl8187_work, which also takes priv->conf_mutex lock. Move cancel_delayed_work_sync out of rtl8187_stop priv->conf_mutex locking region. Reported-by: Larry Finger Tested-by: Larry Finger Signed-off-by: Herton Ronaldo Krzesinski --- drivers/net/wireless/rtl818x/rtl8187_dev.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) diff --git a/drivers/net/wireless/rtl818x/rtl8187_dev.c b/drivers/net/wireless/rtl818x/rtl8187_dev.c index 5830f6c..75b63ac 100644 --- a/drivers/net/wireless/rtl818x/rtl8187_dev.c +++ b/drivers/net/wireless/rtl818x/rtl8187_dev.c @@ -1017,9 +1017,10 @@ static void rtl8187_stop(struct ieee80211_hw *dev) dev_kfree_skb_any(skb); usb_kill_anchored_urbs(&priv->anchored); + mutex_unlock(&priv->conf_mutex); + if (!priv->is_rtl8187b) cancel_delayed_work_sync(&priv->work); - mutex_unlock(&priv->conf_mutex); } static int rtl8187_add_interface(struct ieee80211_hw *dev, -- 1.6.4.1