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authorDaniel J Blueman <daniel.blueman@gmail.com>2011-02-22 00:11:06 +0800
committerJohn W. Linville <linville@tuxdriver.com>2011-02-21 15:14:25 -0500
commit4f919a3bc54da01db829c520ce4b1fabfde1c3f7 (patch)
tree967b25b61b7e0afc261b6c79fe75f3f31644be1b /net/wireless/wext-compat.c
parenta866a2cc1c558089dd4c627eeb300142b1354474 (diff)
downloadlinux-stericsson-4f919a3bc54da01db829c520ce4b1fabfde1c3f7.tar.gz
fix cfg80211_wext_siwfreq lock ordering...
I previously managed to reproduce a hang while scanning wireless channels (reproducible with airodump-ng hopping channels); subsequent lockdep instrumentation revealed a lock ordering issue. Without knowing the design intent, it looks like the locks should be taken in reverse order; please comment. ======================================================= [ INFO: possible circular locking dependency detected ] 2.6.38-rc5-341cd #4 ------------------------------------------------------- airodump-ng/15445 is trying to acquire lock: (&rdev->devlist_mtx){+.+.+.}, at: [<ffffffff816b1266>] cfg80211_wext_siwfreq+0xc6/0x100 but task is already holding lock: (&wdev->mtx){+.+.+.}, at: [<ffffffff816b125c>] cfg80211_wext_siwfreq+0xbc/0x100 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&wdev->mtx){+.+.+.}: [<ffffffff810a79d6>] lock_acquire+0xc6/0x280 [<ffffffff816d6bce>] mutex_lock_nested+0x6e/0x4b0 [<ffffffff81696080>] cfg80211_netdev_notifier_call+0x430/0x5f0 [<ffffffff8109351b>] notifier_call_chain+0x8b/0x100 [<ffffffff810935b1>] raw_notifier_call_chain+0x11/0x20 [<ffffffff81576d92>] call_netdevice_notifiers+0x32/0x60 [<ffffffff815771a4>] __dev_notify_flags+0x34/0x80 [<ffffffff81577230>] dev_change_flags+0x40/0x70 [<ffffffff8158587c>] do_setlink+0x1fc/0x8d0 [<ffffffff81586042>] rtnl_setlink+0xf2/0x140 [<ffffffff81586923>] rtnetlink_rcv_msg+0x163/0x270 [<ffffffff8159d741>] netlink_rcv_skb+0xa1/0xd0 [<ffffffff815867b0>] rtnetlink_rcv+0x20/0x30 [<ffffffff8159d39a>] netlink_unicast+0x2ba/0x300 [<ffffffff8159dd57>] netlink_sendmsg+0x267/0x3e0 [<ffffffff8155e364>] sock_sendmsg+0xe4/0x110 [<ffffffff8155f3a3>] sys_sendmsg+0x253/0x3b0 [<ffffffff81003192>] system_call_fastpath+0x16/0x1b -> #0 (&rdev->devlist_mtx){+.+.+.}: [<ffffffff810a7222>] __lock_acquire+0x1622/0x1d10 [<ffffffff810a79d6>] lock_acquire+0xc6/0x280 [<ffffffff816d6bce>] mutex_lock_nested+0x6e/0x4b0 [<ffffffff816b1266>] cfg80211_wext_siwfreq+0xc6/0x100 [<ffffffff816b2fad>] ioctl_standard_call+0x5d/0xd0 [<ffffffff816b3223>] T.808+0x163/0x170 [<ffffffff816b326a>] wext_handle_ioctl+0x3a/0x90 [<ffffffff815798d2>] dev_ioctl+0x6f2/0x830 [<ffffffff8155cf3d>] sock_ioctl+0xfd/0x290 [<ffffffff8117dffd>] do_vfs_ioctl+0x9d/0x590 [<ffffffff8117e53a>] sys_ioctl+0x4a/0x80 [<ffffffff81003192>] system_call_fastpath+0x16/0x1b other info that might help us debug this: 2 locks held by airodump-ng/15445: #0: (rtnl_mutex){+.+.+.}, at: [<ffffffff81586782>] rtnl_lock+0x12/0x20 #1: (&wdev->mtx){+.+.+.}, at: [<ffffffff816b125c>] cfg80211_wext_siwfreq+0xbc/0x100 stack backtrace: Pid: 15445, comm: airodump-ng Not tainted 2.6.38-rc5-341cd #4 Call Trace: [<ffffffff810a3f0a>] ? print_circular_bug+0xfa/0x100 [<ffffffff810a7222>] ? __lock_acquire+0x1622/0x1d10 [<ffffffff810a1f99>] ? trace_hardirqs_off_caller+0x29/0xc0 [<ffffffff810a79d6>] ? lock_acquire+0xc6/0x280 [<ffffffff816b1266>] ? cfg80211_wext_siwfreq+0xc6/0x100 [<ffffffff810a31d7>] ? mark_held_locks+0x67/0x90 [<ffffffff816d6bce>] ? mutex_lock_nested+0x6e/0x4b0 [<ffffffff816b1266>] ? cfg80211_wext_siwfreq+0xc6/0x100 [<ffffffff810a31d7>] ? mark_held_locks+0x67/0x90 [<ffffffff816b1266>] ? cfg80211_wext_siwfreq+0xc6/0x100 [<ffffffff816b1266>] ? cfg80211_wext_siwfreq+0xc6/0x100 [<ffffffff816b2fad>] ? ioctl_standard_call+0x5d/0xd0 [<ffffffff8157818b>] ? __dev_get_by_name+0x9b/0xc0 [<ffffffff816b2f50>] ? ioctl_standard_call+0x0/0xd0 [<ffffffff816b3223>] ? T.808+0x163/0x170 [<ffffffff8112ddf2>] ? might_fault+0x72/0xd0 [<ffffffff816b326a>] ? wext_handle_ioctl+0x3a/0x90 [<ffffffff8112de3b>] ? might_fault+0xbb/0xd0 [<ffffffff815798d2>] ? dev_ioctl+0x6f2/0x830 [<ffffffff810a1bae>] ? put_lock_stats+0xe/0x40 [<ffffffff810a1c8c>] ? lock_release_holdtime+0xac/0x150 [<ffffffff8155cf3d>] ? sock_ioctl+0xfd/0x290 [<ffffffff8117dffd>] ? do_vfs_ioctl+0x9d/0x590 [<ffffffff8116c8ff>] ? fget_light+0x1df/0x3c0 [<ffffffff8117e53a>] ? sys_ioctl+0x4a/0x80 [<ffffffff81003192>] ? system_call_fastpath+0x16/0x1b Signed-off-by: Daniel J Blueman <daniel.blueman@gmail.com> Acked-by: Johannes Berg <johannes@sipsolutions.net> Signed-off-by: John W. Linville <linville@tuxdriver.com>
Diffstat (limited to 'net/wireless/wext-compat.c')
-rw-r--r--net/wireless/wext-compat.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/net/wireless/wext-compat.c b/net/wireless/wext-compat.c
index 3e5dbd4e4cd5..d112f038edf0 100644
--- a/net/wireless/wext-compat.c
+++ b/net/wireless/wext-compat.c
@@ -802,11 +802,11 @@ int cfg80211_wext_siwfreq(struct net_device *dev,
return freq;
if (freq == 0)
return -EINVAL;
- wdev_lock(wdev);
mutex_lock(&rdev->devlist_mtx);
+ wdev_lock(wdev);
err = cfg80211_set_freq(rdev, wdev, freq, NL80211_CHAN_NO_HT);
- mutex_unlock(&rdev->devlist_mtx);
wdev_unlock(wdev);
+ mutex_unlock(&rdev->devlist_mtx);
return err;
default:
return -EOPNOTSUPP;