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Lockdep reported a possible deadlock with cm_id_priv->lock,
mad_agent_priv->lock and mad_agent_priv->timed_work.timer; this
happens because the mad module does
cancel_delayed_work(&mad_agent_priv->timed_work);
while holding mad_agent_priv->lock. cancel_delayed_work() internally
does del_timer_sync(&mad_agent_priv->timed_work.timer).
This can turn into a deadlock because mad_agent_priv->lock is taken
inside cm_id_priv->lock, so we can get the following set of contexts
that deadlock each other:
A: holding cm_id_priv->lock, waiting for mad_agent_priv->lock
B: holding mad_agent_priv->lock, waiting for del_timer_sync()
C: interrupt during mad_agent_priv->timed_work.timer that takes
cm_id_priv->lock
Fix this by using the new __cancel_delayed_work() interface (which
internally does del_timer() instead of del_timer_sync()) in all the
places where we are holding a lock.
Addresses: http://bugzilla.kernel.org/show_bug.cgi?id=13757
Reported-by: Bart Van Assche <bart.vanassche@gmail.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>
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