linux-kernel - [PATCH 2/4] ntb_perf: send command in response to EAGAIN

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Date:   Wed,  5 Feb 2020 22:46:56 +0530
From:   Arindam Nath <arindam.nath@....com>
To:     Jon Mason <jdmason@...zu.us>, Dave Jiang <dave.jiang@...el.com>,
        Allen Hubbe <allenbh@...il.com>,
        Sanjay R Mehta <sanju.mehta@....com>
Cc:     linux-ntb@...glegroups.com, linux-kernel@...r.kernel.org,
        Arindam Nath <arindam.nath@....com>
Subject: [PATCH 2/4] ntb_perf: send command in response to EAGAIN

perf_spad_cmd_send() and perf_msg_cmd_send() return
-EAGAIN after trying to send commands for a maximum
of MSG_TRIES re-tries. But currently there is no
handling for this error. These functions are invoked
from perf_service_work() through function pointers,
so rather than simply call these functions is not
enough. We need to make sure to invoke them again in
case of -EAGAIN. Since peer status bits were cleared
before calling these functions, we set the same status
bits before queueing the work again for later invocation.
This way we simply won't go ahead and initialize the
XLAT registers wrongfully in case sending the very first
command itself fails.

Signed-off-by: Arindam Nath <arindam.nath@....com>
---
 drivers/ntb/test/ntb_perf.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/drivers/ntb/test/ntb_perf.c b/drivers/ntb/test/ntb_perf.c
index 0e9b9efe74a4..5116655f0211 100644
--- a/drivers/ntb/test/ntb_perf.c
+++ b/drivers/ntb/test/ntb_perf.c
@@ -625,14 +625,24 @@ static void perf_service_work(struct work_struct *work)
 {
 	struct perf_peer *peer = to_peer_service(work);
 
-	if (test_and_clear_bit(PERF_CMD_SSIZE, &peer->sts))
-		perf_cmd_send(peer, PERF_CMD_SSIZE, peer->outbuf_size);
+	if (test_and_clear_bit(PERF_CMD_SSIZE, &peer->sts)) {
+		if (perf_cmd_send(peer, PERF_CMD_SSIZE, peer->outbuf_size)
+		    == -EAGAIN) {
+			set_bit(PERF_CMD_SSIZE, &peer->sts);
+			(void)queue_work(system_highpri_wq, &peer->service);
+		}
+	}
 
 	if (test_and_clear_bit(PERF_CMD_RSIZE, &peer->sts))
 		perf_setup_inbuf(peer);
 
-	if (test_and_clear_bit(PERF_CMD_SXLAT, &peer->sts))
-		perf_cmd_send(peer, PERF_CMD_SXLAT, peer->inbuf_xlat);
+	if (test_and_clear_bit(PERF_CMD_SXLAT, &peer->sts)) {
+		if (perf_cmd_send(peer, PERF_CMD_SXLAT, peer->inbuf_xlat)
+		    == -EAGAIN) {
+			set_bit(PERF_CMD_SXLAT, &peer->sts);
+			(void)queue_work(system_highpri_wq, &peer->service);
+		}
+	}
 
 	if (test_and_clear_bit(PERF_CMD_RXLAT, &peer->sts))
 		perf_setup_outbuf(peer);
-- 
2.17.1