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cfg80211: fix circular lock dependency (1)
Luis reported this lockdep complaint, that he had also reported earlier but when trying to analyse I had been locking at the wrong code, and never saw the problem: (slightly abridged) ======================================================= [ INFO: possible circular locking dependency detected ] 2.6.31-rc4-wl #6 ------------------------------------------------------- wpa_supplicant/3799 is trying to acquire lock: (cfg80211_mutex){+.+.+.}, at: [<ffffffffa009246a>] cfg80211_get_dev_from_ifindex+0x1a/0x90 [cfg80211] but task is already holding lock: (rtnl_mutex){+.+.+.}, at: [<ffffffff81400ff2>] rtnl_lock+0x12/0x20 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (rtnl_mutex){+.+.+.}: [<ffffffff810857b6>] __lock_acquire+0xd76/0x12b0 [<ffffffff81085dd3>] lock_acquire+0xe3/0x120 [<ffffffff814ee7a4>] mutex_lock_nested+0x44/0x350 [<ffffffff81400ff2>] rtnl_lock+0x12/0x20 [<ffffffffa009f6a5>] nl80211_send_reg_change_event+0x1f5/0x2a0 [cfg80211] [<ffffffffa009529e>] set_regdom+0x28e/0x4c0 [cfg80211] -> #0 (cfg80211_mutex){+.+.+.}: [<ffffffff8108587b>] __lock_acquire+0xe3b/0x12b0 [<ffffffff81085dd3>] lock_acquire+0xe3/0x120 [<ffffffff814ee7a4>] mutex_lock_nested+0x44/0x350 [<ffffffffa009246a>] cfg80211_get_dev_from_ifindex+0x1a/0x90 [cfg80211] [<ffffffffa009813f>] get_rdev_dev_by_info_ifindex+0x6f/0xa0 [cfg80211] [<ffffffffa009b12b>] nl80211_set_interface+0x3b/0x260 [cfg80211] When looking at the correct code, the problem is quite obvious. I'm not entirely sure which code paths lead here, so until I can analyse it better let's just use RCU to avoid the problem. Signed-off-by: Johannes Berg <johannes@sipsolutions.net> Signed-off-by: John W. Linville <linville@tuxdriver.com>
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1 changed files with 3 additions and 3 deletions
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@ -4517,10 +4517,10 @@ void nl80211_send_reg_change_event(struct regulatory_request *request)
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return;
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}
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rtnl_lock();
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rcu_read_lock();
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genlmsg_multicast_allns(msg, 0, nl80211_regulatory_mcgrp.id,
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GFP_KERNEL);
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rtnl_unlock();
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GFP_ATOMIC);
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rcu_read_unlock();
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return;
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