queue-4.19/ib-hfi1-avoid-hardlockup-with-flushlist_lock.patch

   1 From 5b1058c9eafcafe88a8bd4c664fc904a44d21aca Mon Sep 17 00:00:00 2001
   2 From: Mike Marciniszyn <mike.marciniszyn@intel.com>
   3 Date: Mon, 24 Jun 2019 12:14:29 -0400
   4 Subject: IB/hfi1: Avoid hardlockup with flushlist_lock
   5
   6 commit cf131a81967583ae737df6383a0893b9fee75b4e upstream.
   7
   8 Heavy contention of the sde flushlist_lock can cause hard lockups at
   9 extreme scale when the flushing logic is under stress.
  10
  11 Mitigate by replacing the item at a time copy to the local list with
  12 an O(1) list_splice_init() and using the high priority work queue to
  13 do the flushes.
  14
  15 Ported to linux-4.14.y.
  16
  17 Fixes: 7724105686e7 ("IB/hfi1: add driver files")
  18 Cc: <stable@vger.kernel.org>
  19 Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
  20 Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
  21 Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
  22 Signed-off-by: Doug Ledford <dledford@redhat.com>
  23 Signed-off-by: Sasha Levin <sashal@kernel.org>
  24 ---
  25  drivers/infiniband/hw/hfi1/sdma.c | 9 +++------
  26  1 file changed, 3 insertions(+), 6 deletions(-)
  27
  28 diff --git a/drivers/infiniband/hw/hfi1/sdma.c b/drivers/infiniband/hw/hfi1/sdma.c
  29 index 88e326d6cc49..d648a4167832 100644
  30 --- a/drivers/infiniband/hw/hfi1/sdma.c
  31 +++ b/drivers/infiniband/hw/hfi1/sdma.c
  32 @@ -410,10 +410,7 @@ static void sdma_flush(struct sdma_engine *sde)
  33         sdma_flush_descq(sde);
  34         spin_lock_irqsave(&sde->flushlist_lock, flags);
  35         /* copy flush list */
  36 -       list_for_each_entry_safe(txp, txp_next, &sde->flushlist, list) {
  37 -               list_del_init(&txp->list);
  38 -               list_add_tail(&txp->list, &flushlist);
  39 -       }
  40 +       list_splice_init(&sde->flushlist, &flushlist);
  41         spin_unlock_irqrestore(&sde->flushlist_lock, flags);
  42         /* flush from flush list */
  43         list_for_each_entry_safe(txp, txp_next, &flushlist, list)
  44 @@ -2426,7 +2423,7 @@ int sdma_send_txreq(struct sdma_engine *sde,
  45                 wait->tx_count++;
  46                 wait->count += tx->num_desc;
  47         }
  48 -       schedule_work(&sde->flush_worker);
  49 +       queue_work_on(sde->cpu, system_highpri_wq, &sde->flush_worker);
  50         ret = -ECOMM;
  51         goto unlock;
  52  nodesc:
  53 @@ -2526,7 +2523,7 @@ int sdma_send_txlist(struct sdma_engine *sde, struct iowait *wait,
  54                 }
  55         }
  56         spin_unlock(&sde->flushlist_lock);
  57 -       schedule_work(&sde->flush_worker);
  58 +       queue_work_on(sde->cpu, system_highpri_wq, &sde->flush_worker);
  59         ret = -ECOMM;
  60         goto update_tail;
  61  nodesc:
  62 --
  63 2.20.1
  64