From: Roland Dreier Date: Mon, 7 Sep 2009 15:27:50 +0000 (-0700) Subject: IB/mad: Fix possible lock-lock-timer deadlock X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=6b2eef8fd78ff909c3396b8671d57c42559cc51d;p=linux-beck.git IB/mad: Fix possible lock-lock-timer deadlock 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 Signed-off-by: Roland Dreier --- diff --git a/drivers/infiniband/core/mad.c b/drivers/infiniband/core/mad.c index de922a04ca2d..bc30c00c5d7a 100644 --- a/drivers/infiniband/core/mad.c +++ b/drivers/infiniband/core/mad.c @@ -1974,7 +1974,7 @@ static void adjust_timeout(struct ib_mad_agent_private *mad_agent_priv) unsigned long delay; if (list_empty(&mad_agent_priv->wait_list)) { - cancel_delayed_work(&mad_agent_priv->timed_work); + __cancel_delayed_work(&mad_agent_priv->timed_work); } else { mad_send_wr = list_entry(mad_agent_priv->wait_list.next, struct ib_mad_send_wr_private, @@ -1983,7 +1983,7 @@ static void adjust_timeout(struct ib_mad_agent_private *mad_agent_priv) if (time_after(mad_agent_priv->timeout, mad_send_wr->timeout)) { mad_agent_priv->timeout = mad_send_wr->timeout; - cancel_delayed_work(&mad_agent_priv->timed_work); + __cancel_delayed_work(&mad_agent_priv->timed_work); delay = mad_send_wr->timeout - jiffies; if ((long)delay <= 0) delay = 1; @@ -2023,7 +2023,7 @@ static void wait_for_response(struct ib_mad_send_wr_private *mad_send_wr) /* Reschedule a work item if we have a shorter timeout */ if (mad_agent_priv->wait_list.next == &mad_send_wr->agent_list) { - cancel_delayed_work(&mad_agent_priv->timed_work); + __cancel_delayed_work(&mad_agent_priv->timed_work); queue_delayed_work(mad_agent_priv->qp_info->port_priv->wq, &mad_agent_priv->timed_work, delay); }