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ocfs2: fix deadlock between o2hb thread and o2net_wq
The following case may lead to o2net_wq and o2hb thread deadlock on o2hb_callback_sem. Currently there are 2 nodes say N1, N2 in the cluster. And N2 down, at the same time, N3 tries to join the cluster. So N1 will handle node down (N2) and join (N3) simultaneously. o2hb o2net_wq ->o2hb_do_disk_heartbeat ->o2hb_check_slot ->o2hb_run_event_list ->o2hb_fire_callbacks ->down_write(&o2hb_callback_sem) ->o2net_hb_node_down_cb ->flush_workqueue(o2net_wq) ->o2net_process_message ->dlm_query_join_handler ->o2hb_check_node_heartbeating ->o2hb_fill_node_map ->down_read(&o2hb_callback_sem) No need to take o2hb_callback_sem in dlm_query_join_handler, o2hb_live_lock is enough to protect live node map. Signed-off-by: Joseph Qi <[email protected]> Cc: xMark Fasheh <[email protected]> Cc: Joel Becker <[email protected]> Cc: jiangyiwen <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
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