Commit 3db7d8f0 authored by Mike Marciniszyn's avatar Mike Marciniszyn Committed by Greg Kroah-Hartman

IB/hfi1: Avoid hardlockup with flushlist_lock

commit cf131a81 upstream.

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>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent c2df772b
......@@ -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:
......
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