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    Subject[PATCH AUTOSEL 5.8 24/42] hv_utils: drain the timesync packets on onchannelcallback
    Date
    From: Vineeth Pillai <viremana@linux.microsoft.com>

    [ Upstream commit b46b4a8a57c377b72a98c7930a9f6969d2d4784e ]

    There could be instances where a system stall prevents the timesync
    packets 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>
    Reviewed-by: Michael Kelley <mikelley@microsoft.com>
    Link: https://lore.kernel.org/r/20200821152849.99517-1-viremana@linux.microsoft.com
    Signed-off-by: Wei Liu <wei.liu@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    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 1f86e8d9b018d..a4e8d96513c22 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)];

    --
    2.25.1
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