linux-kernel - [PATCH 3.10 303/319] hv: do not lose pending heartbeat vmbus packets

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Date:   Sun,  5 Feb 2017 20:22:05 +0100
From:   Willy Tarreau <w@....eu>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux@...ck-us.net
Cc:     Long Li <longli@...rosoft.com>,
        "K . Y . Srinivasan" <kys@...rosoft.com>, Willy Tarreau <w@....eu>
Subject: [PATCH 3.10 303/319] hv: do not lose pending heartbeat vmbus packets

From: Long Li <longli@...rosoft.com>

commit 407a3aee6ee2d2cb46d9ba3fc380bc29f35d020c upstream.

The host keeps sending heartbeat packets independent of the
guest responding to them.  Even though we respond to the heartbeat messages at
interrupt level, we can have situations where there maybe multiple heartbeat
messages pending that have not been responded to. For instance this occurs when the
VM is paused and the host continues to send the heartbeat messages.
Address this issue by draining and responding to all
the heartbeat messages that maybe pending.

Signed-off-by: Long Li <longli@...rosoft.com>
Signed-off-by: K. Y. Srinivasan <kys@...rosoft.com>
Signed-off-by: Willy Tarreau <w@....eu>
---
 drivers/hv/hv_util.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/hv/hv_util.c b/drivers/hv/hv_util.c
index 64c778f..5f69c83 100644
--- a/drivers/hv/hv_util.c
+++ b/drivers/hv/hv_util.c
@@ -244,10 +244,14 @@ static void heartbeat_onchannelcallback(void *context)
 	struct heartbeat_msg_data *heartbeat_msg;
 	u8 *hbeat_txf_buf = util_heartbeat.recv_buffer;
 
-	vmbus_recvpacket(channel, hbeat_txf_buf,
-			 PAGE_SIZE, &recvlen, &requestid);
+	while (1) {
+
+		vmbus_recvpacket(channel, hbeat_txf_buf,
+				 PAGE_SIZE, &recvlen, &requestid);
+
+		if (!recvlen)
+			break;
 
-	if (recvlen > 0) {
 		icmsghdrp = (struct icmsg_hdr *)&hbeat_txf_buf[
 				sizeof(struct vmbuspipe_hdr)];
 
-- 
2.8.0.rc2.1.gbe9624a