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FAILED: patch "[PATCH] IB/hfi1: Avoid hardlockup with flushlist_lock" failed to apply to 4.9-stable tree

PATCH [email protected] 1 participant 1 message Jun 23, 2019

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Stable branch InfiniBand HFI1 driver
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The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From cf131a81967583ae737df6383a0893b9fee75b4e Mon Sep 17 00:00:00 2001
From: Mike Marciniszyn <[email protected]>
Date: Fri, 14 Jun 2019 12:32:26 -0400
Subject: [PATCH] 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 7724105686e7 ("IB/hfi1: add driver files")
Cc <[email protected]>
Reviewed-by Dennis Dalessandro <[email protected]>
Signed-off-by Mike Marciniszyn <[email protected]>
Signed-off-by Dennis Dalessandro <[email protected]>
Signed-off-by Doug Ledford <[email protected]>
drivers/infiniband/hw/hfi1/sdma.c +3 -6
index b0110728f541..70828de7436b 100644
@@ -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: