[PATCH v2] hv_utils: drain the timesync packets on onchannelcallback

[PATCH v2] hv_utils: drain the timesync packets on onchannelcallback

[Vineeth Pillai]

There could be instances where a system stall prevents the timesync
packaets to be consumed. And this might lead to more than one packet
pending in the ring buffer. Current code empties one packet per callback
and it might be a stale one. So drain all the packets from ring buffer
on each callback.

Signed-off-by: Vineeth Pillai <viremana@linux.microsoft.com>
---

 v2:
    - s/pr_warn/pr_warn_once/
    
---
 drivers/hv/hv_util.c | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/drivers/hv/hv_util.c b/drivers/hv/hv_util.c
index 1f86e8d9b018..a4e8d96513c2 100644
--- a/drivers/hv/hv_util.c
+++ b/drivers/hv/hv_util.c
@@ -387,10 +387,23 @@ static void timesync_onchannelcallback(void *context)
 	struct ictimesync_ref_data *refdata;
 	u8 *time_txf_buf = util_timesynch.recv_buffer;
 
-	vmbus_recvpacket(channel, time_txf_buf,
-			 HV_HYP_PAGE_SIZE, &recvlen, &requestid);
+	/*
+	 * Drain the ring buffer and use the last packet to update
+	 * host_ts
+	 */
+	while (1) {
+		int ret = vmbus_recvpacket(channel, time_txf_buf,
+					   HV_HYP_PAGE_SIZE, &recvlen,
+					   &requestid);
+		if (ret) {
+			pr_warn_once("TimeSync IC pkt recv failed (Err: %d)\n",
+				     ret);
+			break;
+		}
+
+		if (!recvlen)
+			break;
 
-	if (recvlen > 0) {
 		icmsghdrp = (struct icmsg_hdr *)&time_txf_buf[
 				sizeof(struct vmbuspipe_hdr)];
 
-- 
2.17.1

RE: [PATCH v2] hv_utils: drain the timesync packets on onchannelcallback

[Michael Kelley]

From: viremana@linux.microsoft.com Sent: Friday, August 21, 2020 8:29 AM
> 
> There could be instances where a system stall prevents the timesync
> packaets to be consumed. And this might lead to more than one packet
> pending in the ring buffer. Current code empties one packet per callback
> and it might be a stale one. So drain all the packets from ring buffer
> on each callback.
> 
> Signed-off-by: Vineeth Pillai <viremana@linux.microsoft.com>
> ---
> 
>  v2:
>     - s/pr_warn/pr_warn_once/
> 
> ---
>  drivers/hv/hv_util.c | 19 ++++++++++++++++---
>  1 file changed, 16 insertions(+), 3 deletions(-)

Reviewed-by: Michael Kelley <mikelley@microsoft.com>

Re: [PATCH v2] hv_utils: drain the timesync packets on onchannelcallback

[Wei Liu]

On Fri, Aug 21, 2020 at 03:28:49PM +0000, Vineeth Pillai wrote:
> There could be instances where a system stall prevents the timesync
> packaets to be consumed. And this might lead to more than one packet

Typo "packaet".

No need to resend. I can fix this while committing this patch.

Wei.

Re: [PATCH v2] hv_utils: drain the timesync packets on onchannelcallback

[Vineeth Pillai]

> Typo "packaet".
>
> No need to resend. I can fix this while committing this patch.

Thanks Wei.

Re: [PATCH v2] hv_utils: drain the timesync packets on onchannelcallback

[Wei Liu]

On Sun, Aug 23, 2020 at 08:15:41AM -0400, Vineeth Pillai wrote:
> 
> > Typo "packaet".
> > 
> > No need to resend. I can fix this while committing this patch.
> 
> Thanks Wei.
> 
> 

Applied to hyperv-fixes. Thanks.