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Linux kernel source tree
9707a015fe
6lowpan.c has theoretically conflicting lock orderings, which lockdep
complains about:
a) rtnl_lock > hdev->workqueue
from 6lowpan.c:delete_netdev -> rtnl_lock -> device_del
-> put_device(parent) -> hci_release_dev -> destroy_workqueue
b) hdev->workqueue > l2cap_conn->lock > chan->lock > rtnl_lock
from hci_rx_work -> 6lowpan.c:chan_ready_cb
-> lowpan_register_netdev, ifup -> rtnl_lock
Actual deadlock appears not possible, as hci_rx_work is disabled and
l2cap_conn flushed already on hdev unregister. Hence, do minimal thing
to make lockdep happy by breaking chain a) by holding hdev refcount
until after netdev put in 6lowpan.c.
Fixes the lockdep complaint:
WARNING: possible circular locking dependency detected.
kworker/0:1/11 is trying to acquire lock:
ffff8880023b3940 ((wq_completion)hci0#2){+.+.}-{0:0}, at: touch_wq_lockdep_map+0x8b/0x130
but task is already holding lock:
ffffffff95e4f9c0 (rtnl_mutex){+.+.}-{4:4}, at: lowpan_unregister_netdev+0xd/0x30
Workqueue: events delete_netdev
Signed-off-by: Pauli Virtanen <pav@iki.fi>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
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Linux kernel ============ The Linux kernel is the core of any Linux operating system. It manages hardware, system resources, and provides the fundamental services for all other software. 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