From 0e442afd92fcdde2cc63b6f25556b8934e42b7d2 Mon Sep 17 00:00:00 2001 From: Roland Dreier Date: Wed, 23 Sep 2009 11:10:15 -0700 Subject: [PATCH] IB/mad: Fix lock-lock-timer deadlock in RMPP code Holding agent->lock across cancel_delayed_work() (which does del_timer_sync()) in ib_cancel_rmpp_recvs() leads to lockdep reports of possible lock-timer deadlocks if a consumer ever does something that connects agent->lock to a lock taken in IRQ context (cf http://marc.info/?l=linux-rdma&m=125243699026045). Fix this by changing the list items to a new state "CANCELING" while holding the lock, and then canceling the delayed work without holding the lock. If the delayed work runs after the lock is dropped, it will see the state is CANCELING and return immediately, so the list will stay stable while we traverse it with the lock not held. Reviewed-by: Sean Hefty Signed-off-by: Roland Dreier --- drivers/infiniband/core/mad_rmpp.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) diff --git a/drivers/infiniband/core/mad_rmpp.c b/drivers/infiniband/core/mad_rmpp.c index 57a3c6f947b..4e0f2829e0e 100644 --- a/drivers/infiniband/core/mad_rmpp.c +++ b/drivers/infiniband/core/mad_rmpp.c @@ -37,7 +37,8 @@ enum rmpp_state { RMPP_STATE_ACTIVE, RMPP_STATE_TIMEOUT, - RMPP_STATE_COMPLETE + RMPP_STATE_COMPLETE, + RMPP_STATE_CANCELING }; struct mad_rmpp_recv { @@ -86,19 +87,23 @@ void ib_cancel_rmpp_recvs(struct ib_mad_agent_private *agent) unsigned long flags; spin_lock_irqsave(&agent->lock, flags); + list_for_each_entry(rmpp_recv, &agent->rmpp_list, list) { + if (rmpp_recv->state != RMPP_STATE_COMPLETE) + ib_free_recv_mad(rmpp_recv->rmpp_wc); + rmpp_recv->state = RMPP_STATE_CANCELING; + } + spin_unlock_irqrestore(&agent->lock, flags); + list_for_each_entry(rmpp_recv, &agent->rmpp_list, list) { cancel_delayed_work(&rmpp_recv->timeout_work); cancel_delayed_work(&rmpp_recv->cleanup_work); } - spin_unlock_irqrestore(&agent->lock, flags); flush_workqueue(agent->qp_info->port_priv->wq); list_for_each_entry_safe(rmpp_recv, temp_rmpp_recv, &agent->rmpp_list, list) { list_del(&rmpp_recv->list); - if (rmpp_recv->state != RMPP_STATE_COMPLETE) - ib_free_recv_mad(rmpp_recv->rmpp_wc); destroy_rmpp_recv(rmpp_recv); } } @@ -260,6 +265,10 @@ static void recv_cleanup_handler(struct work_struct *work) unsigned long flags; spin_lock_irqsave(&rmpp_recv->agent->lock, flags); + if (rmpp_recv->state == RMPP_STATE_CANCELING) { + spin_unlock_irqrestore(&rmpp_recv->agent->lock, flags); + return; + } list_del(&rmpp_recv->list); spin_unlock_irqrestore(&rmpp_recv->agent->lock, flags); destroy_rmpp_recv(rmpp_recv); -- 2.20.1