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authorMoni Shoua <monis@Voltaire.COM>2008-07-15 02:48:43 -0400
committerRoland Dreier <rolandd@cisco.com>2008-07-15 02:48:43 -0400
commit164ba0893c27a216557396320b6063fdac040392 (patch)
tree257f56ce914584f1a26112d86f1737c27671a096
parenta9474917099e007c0f51d5474394b5890111614f (diff)
IB/sa: Fail requests made while creating new SM AH
This patch solves a race that occurs after an event occurs that causes the SA query module to flush its SM address handle (AH). When SM AH becomes invalid and needs an update it is handled by the global workqueue. On the other hand this event is also handled in the IPoIB driver by queuing work in the ipoib_workqueue that does multicast joins. Although queuing is in the right order, it is done to 2 different workqueues and so there is no guarantee that the first to be queued is the first to be executed. This causes a problem because IPoIB may end up sending an request to the old SM, which will take a long time to time out (since the old SM is gone); this leads to a much longer than necessary interruption in multicast traffer. The patch sets the SA query module's SM AH to NULL when the event occurs, and until update_sm_ah() is done, any request that needs sm_ah fails with -EAGAIN return status. For consumers, the patch doesn't make things worse. Before the patch, MADs are sent to the wrong SM so the request gets lost. Consumers can be improved if they examine the return code and respond to EAGAIN properly but even without an improvement the situation is not getting worse. Signed-off-by: Moni Levy <monil@voltaire.com> Signed-off-by: Moni Shoua <monis@voltaire.com> Signed-off-by: Roland Dreier <rolandd@cisco.com>
-rw-r--r--drivers/infiniband/core/sa_query.c22
1 files changed, 16 insertions, 6 deletions
diff --git a/drivers/infiniband/core/sa_query.c b/drivers/infiniband/core/sa_query.c
index cf474ec27070..78ea8157d622 100644
--- a/drivers/infiniband/core/sa_query.c
+++ b/drivers/infiniband/core/sa_query.c
@@ -361,7 +361,7 @@ static void update_sm_ah(struct work_struct *work)
361{ 361{
362 struct ib_sa_port *port = 362 struct ib_sa_port *port =
363 container_of(work, struct ib_sa_port, update_task); 363 container_of(work, struct ib_sa_port, update_task);
364 struct ib_sa_sm_ah *new_ah, *old_ah; 364 struct ib_sa_sm_ah *new_ah;
365 struct ib_port_attr port_attr; 365 struct ib_port_attr port_attr;
366 struct ib_ah_attr ah_attr; 366 struct ib_ah_attr ah_attr;
367 367
@@ -397,12 +397,9 @@ static void update_sm_ah(struct work_struct *work)
397 } 397 }
398 398
399 spin_lock_irq(&port->ah_lock); 399 spin_lock_irq(&port->ah_lock);
400 old_ah = port->sm_ah;
401 port->sm_ah = new_ah; 400 port->sm_ah = new_ah;
402 spin_unlock_irq(&port->ah_lock); 401 spin_unlock_irq(&port->ah_lock);
403 402
404 if (old_ah)
405 kref_put(&old_ah->ref, free_sm_ah);
406} 403}
407 404
408static void ib_sa_event(struct ib_event_handler *handler, struct ib_event *event) 405static void ib_sa_event(struct ib_event_handler *handler, struct ib_event *event)
@@ -413,8 +410,17 @@ static void ib_sa_event(struct ib_event_handler *handler, struct ib_event *event
413 event->event == IB_EVENT_PKEY_CHANGE || 410 event->event == IB_EVENT_PKEY_CHANGE ||
414 event->event == IB_EVENT_SM_CHANGE || 411 event->event == IB_EVENT_SM_CHANGE ||
415 event->event == IB_EVENT_CLIENT_REREGISTER) { 412 event->event == IB_EVENT_CLIENT_REREGISTER) {
416 struct ib_sa_device *sa_dev; 413 unsigned long flags;
417 sa_dev = container_of(handler, typeof(*sa_dev), event_handler); 414 struct ib_sa_device *sa_dev =
415 container_of(handler, typeof(*sa_dev), event_handler);
416 struct ib_sa_port *port =
417 &sa_dev->port[event->element.port_num - sa_dev->start_port];
418
419 spin_lock_irqsave(&port->ah_lock, flags);
420 if (port->sm_ah)
421 kref_put(&port->sm_ah->ref, free_sm_ah);
422 port->sm_ah = NULL;
423 spin_unlock_irqrestore(&port->ah_lock, flags);
418 424
419 schedule_work(&sa_dev->port[event->element.port_num - 425 schedule_work(&sa_dev->port[event->element.port_num -
420 sa_dev->start_port].update_task); 426 sa_dev->start_port].update_task);
@@ -519,6 +525,10 @@ static int alloc_mad(struct ib_sa_query *query, gfp_t gfp_mask)
519 unsigned long flags; 525 unsigned long flags;
520 526
521 spin_lock_irqsave(&query->port->ah_lock, flags); 527 spin_lock_irqsave(&query->port->ah_lock, flags);
528 if (!query->port->sm_ah) {
529 spin_unlock_irqrestore(&query->port->ah_lock, flags);
530 return -EAGAIN;
531 }
522 kref_get(&query->port->sm_ah->ref); 532 kref_get(&query->port->sm_ah->ref);
523 query->sm_ah = query->port->sm_ah; 533 query->sm_ah = query->port->sm_ah;
524 spin_unlock_irqrestore(&query->port->ah_lock, flags); 534 spin_unlock_irqrestore(&query->port->ah_lock, flags);