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FAILED: patch "[PATCH] IB/hfi1: Close PSM sdma_progress sleep window" failed to apply to 4.4-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 4.4-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 da9de5f8527f4b9efc82f967d29a583318c034c7 Mon Sep 17 00:00:00 2001
From: Mike Marciniszyn <[email protected]>
Date: Fri, 7 Jun 2019 08:25:31 -0400
Subject: [PATCH] IB/hfi1: Close PSM sdma_progress sleep window

The call to sdma_progress() is called outside the wait lock.

In this case, there is a race condition where sdma_progress() can return false and the sdma_engine can idle. If that happens, there will be no more sdma interrupts to cause the wakeup and the user_sdma xmit will hang.

Fix by moving the lock to enclose the sdma_progress() call.

Also, delete busycount. The need for this was removed by:
commit bcad29137a97 ("IB/hfi1: Serve the most starved iowait entry first")

Cc <[email protected]>
Fixes 7724105686e7 ("IB/hfi1: add driver files")
Reviewed-by Gary Leshner <[email protected]>
Signed-off-by Mike Marciniszyn <[email protected]>
Signed-off-by Dennis Dalessandro <[email protected]>
Signed-off-by Jason Gunthorpe <[email protected]>
drivers/infiniband/hw/hfi1/user_sdma.c +4 -8
index 8bfbc6d7ea34..fd754a16475a 100644
@@ -130,20 +130,16 @@ static int defer_packet_queue(
 {
 	struct hfi1_user_sdma_pkt_q *pq =
 		container_of(wait->iow, struct hfi1_user_sdma_pkt_q, busy);
-	struct user_sdma_txreq *tx =
-		container_of(txreq, struct user_sdma_txreq, txreq);
 
-	if (sdma_progress(sde, seq, txreq)) {
-		if (tx->busycount++ < MAX_DEFER_RETRY_COUNT)
-			goto eagain;
-	}
+	write_seqlock(&sde->waitlock);
+	if (sdma_progress(sde, seq, txreq))
+		goto eagain;
 	/*
 	 * We are assuming that if the list is enqueued somewhere, it
 	 * is to the dmawait list since that is the only place where
 	 * it is supposed to be enqueued.
 	 */
 	xchg(&pq->state, SDMA_PKT_Q_DEFERRED);
-	write_seqlock(&sde->waitlock);
 	if (list_empty(&pq->busy.list)) {
 		iowait_get_priority(&pq->busy);
 		iowait_queue(pkts_sent, &pq->busy, &sde->dmawait);

@@ -151,6 +147,7 @@ static int defer_packet_queue(
 	write_sequnlock(&sde->waitlock);
 	return -EBUSY;
 eagain:
+	write_sequnlock(&sde->waitlock);
 	return -EAGAIN;
 }
 

@@ -804,7 +801,6 @@ static int user_sdma_send_pkts(struct user_sdma_request *req, u16 maxpkts)
 
 		tx->flags = 0;
 		tx->req = req;
-		tx->busycount = 0;
 		INIT_LIST_HEAD(&tx->list);
 
 		/*
drivers/infiniband/hw/hfi1/user_sdma.h +0 -1
index 14dfd757dafd..4d8510b0fc38 100644
@@ -245,7 +245,6 @@ struct user_sdma_txreq {
 	struct list_head list;
 	struct user_sdma_request *req;
 	u16 flags;
-	unsigned int busycount;
 	u16 seqnum;
 };