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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 <bart.vanassche@gmail.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>
This commit is contained in:
Roland Dreier 2009-09-07 08:27:50 -07:00
parent 60f2b652f5
commit 6b2eef8fd7
1 changed files with 3 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
drivers/infiniband/core/mad.c
View File

@ -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);
}