linux-kernel - [PATCH 5.4 054/147] IB/hfi1: Fix another case where pq is left on waitlist

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Date:   Mon, 18 May 2020 19:36:17 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Kaike Wan <kaike.wan@...el.com>,
        Mike Marciniszyn <mike.marciniszyn@...el.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 054/147] IB/hfi1: Fix another case where pq is left on waitlist

From: Mike Marciniszyn <mike.marciniszyn@...el.com>

[ Upstream commit fa8dac3968635dec8518a13ac78d662f2aa88e4d ]

The commit noted below fixed a case where a pq is left on the sdma wait
list.

It however missed another case.

user_sdma_send_pkts() has two calls from hfi1_user_sdma_process_request().

If the first one fails as indicated by -EBUSY, the pq will be placed on
the waitlist as by design.

If the second call then succeeds, the pq is still on the waitlist setting
up a race with the interrupt handler if a subsequent request uses a
different SDMA engine

Fix by deleting the first call.

The use of pcount and the intent to send a short burst of packets followed
by the larger balance of packets was never correctly implemented, because
the two calls always send pcount packets no matter what.  A subsequent
patch will correct that issue.

Fixes: 9a293d1e21a6 ("IB/hfi1: Ensure pq is not left on waitlist")
Link: https://lore.kernel.org/r/20200504130917.175613.43231.stgit@awfm-01.aw.intel.com
Cc: <stable@...r.kernel.org>
Reviewed-by: Kaike Wan <kaike.wan@...el.com>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@...el.com>
Signed-off-by: Jason Gunthorpe <jgg@...lanox.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/infiniband/hw/hfi1/user_sdma.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/drivers/infiniband/hw/hfi1/user_sdma.c b/drivers/infiniband/hw/hfi1/user_sdma.c
index 13e4203497b33..a92346e88628b 100644
--- a/drivers/infiniband/hw/hfi1/user_sdma.c
+++ b/drivers/infiniband/hw/hfi1/user_sdma.c
@@ -589,10 +589,6 @@ int hfi1_user_sdma_process_request(struct hfi1_filedata *fd,
 
 	set_comp_state(pq, cq, info.comp_idx, QUEUED, 0);
 	pq->state = SDMA_PKT_Q_ACTIVE;
-	/* Send the first N packets in the request to buy us some time */
-	ret = user_sdma_send_pkts(req, pcount);
-	if (unlikely(ret < 0 && ret != -EBUSY))
-		goto free_req;
 
 	/*
 	 * This is a somewhat blocking send implementation.
-- 
2.20.1