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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Young Xiao <YangX92@hotmail.com>,
        Jens Axboe <axboe@kernel.dk>, Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.20 087/352] sunvdc: Do not spin in an infinite loop when vio_ldc_send() returns EAGAIN
Date:   Mon, 11 Feb 2019 15:15:14 +0100
Message-Id: <20190211141851.477327773@linuxfoundation.org>
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4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

[ Upstream commit a11f6ca9aef989b56cd31ff4ee2af4fb31a172ec ]

__vdc_tx_trigger should only loop on EAGAIN a finite
number of times.

See commit adddc32d6fde ("sunvnet: Do not spin in an
infinite loop when vio_ldc_send() returns EAGAIN") for detail.

Signed-off-by: Young Xiao <YangX92@hotmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/block/sunvdc.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/block/sunvdc.c b/drivers/block/sunvdc.c
index b54fa6726303..6b7b0d8a2acb 100644
--- a/drivers/block/sunvdc.c
+++ b/drivers/block/sunvdc.c
@@ -45,6 +45,8 @@ MODULE_VERSION(DRV_MODULE_VERSION);
 #define WAITING_FOR_GEN_CMD	0x04
 #define WAITING_FOR_ANY		-1
 
+#define	VDC_MAX_RETRIES	10
+
 static struct workqueue_struct *sunvdc_wq;
 
 struct vdc_req_entry {
@@ -431,6 +433,7 @@ static int __vdc_tx_trigger(struct vdc_port *port)
 		.end_idx		= dr->prod,
 	};
 	int err, delay;
+	int retries = 0;
 
 	hdr.seq = dr->snd_nxt;
 	delay = 1;
@@ -443,6 +446,8 @@ static int __vdc_tx_trigger(struct vdc_port *port)
 		udelay(delay);
 		if ((delay <<= 1) > 128)
 			delay = 128;
+		if (retries++ > VDC_MAX_RETRIES)
+			break;
 	} while (err == -EAGAIN);
 
 	if (err == -ENOTCONN)
-- 
2.19.1