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Commit cf131a81 authored by Mike Marciniszyn's avatar Mike Marciniszyn Committed by Doug Ledford
Browse files

IB/hfi1: Avoid hardlockup with flushlist_lock 



Heavy contention of the sde flushlist_lock can cause hard lockups at
extreme scale when the flushing logic is under stress.

Mitigate by replacing the item at a time copy to the local list with
an O(1) list_splice_init() and using the high priority work queue to
do the flushes.

Fixes: 77241056 ("IB/hfi1: add driver files")
Cc: <stable@vger.kernel.org>
Reviewed-by: default avatarDennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: default avatarMike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: default avatarDennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: default avatarDoug Ledford <dledford@redhat.com>
parent cc78076a

drivers/infiniband/hw/hfi1/sdma.c

+3 −6
Original line number Diff line number Diff line
@@ -410,10 +410,7 @@ static void sdma_flush(struct sdma_engine *sde) 
	sdma_flush_descq(sde);

	spin_lock_irqsave(&sde->flushlist_lock, flags);

	/* copy flush list */

	list_for_each_entry_safe(txp, txp_next, &sde->flushlist, list) {

		list_del_init(&txp->list);

		list_add_tail(&txp->list, &flushlist);

	}

	list_splice_init(&sde->flushlist, &flushlist);

	spin_unlock_irqrestore(&sde->flushlist_lock, flags);

	/* flush from flush list */

	list_for_each_entry_safe(txp, txp_next, &flushlist, list)
@@ -2413,7 +2410,7 @@ int sdma_send_txreq(struct sdma_engine *sde, 
	list_add_tail(&tx->list, &sde->flushlist);

	spin_unlock(&sde->flushlist_lock);

	iowait_inc_wait_count(wait, tx->num_desc);

	schedule_work(&sde->flush_worker);

	queue_work_on(sde->cpu, system_highpri_wq, &sde->flush_worker);

	ret = -ECOMM;

	goto unlock;

nodesc:
@@ -2511,7 +2508,7 @@ int sdma_send_txlist(struct sdma_engine *sde, struct iowait_work *wait, 
		iowait_inc_wait_count(wait, tx->num_desc);

	}

	spin_unlock(&sde->flushlist_lock);

	schedule_work(&sde->flush_worker);

	queue_work_on(sde->cpu, system_highpri_wq, &sde->flush_worker);

	ret = -ECOMM;

	goto update_tail;

nodesc: