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    Subject[RFC PATCH 18/60] hyper_dmabuf: reset comm channel when one end has disconnected.
    Date
    From: Mateusz Polrola <mateuszx.potrola@intel.com>

    When exporter or importer is disconnected, ring buffer should be
    reinitialzed, otherwise on next reconnection exporter/importer will
    receive old requests/responses remaining in the ring buffer, which are
    not valid anymore.

    This patch also blocks back ring irq until communication channel is
    initialized and fully active to prevent a race condition.

    Signed-off-by: Dongwon Kim <dongwon.kim@intel.com>
    ---
    .../xen/hyper_dmabuf/xen/hyper_dmabuf_xen_comm.c | 24 +++++++++++++++++++---
    1 file changed, 21 insertions(+), 3 deletions(-)

    diff --git a/drivers/xen/hyper_dmabuf/xen/hyper_dmabuf_xen_comm.c b/drivers/xen/hyper_dmabuf/xen/hyper_dmabuf_xen_comm.c
    index 5e7a250..b629032 100644
    --- a/drivers/xen/hyper_dmabuf/xen/hyper_dmabuf_xen_comm.c
    +++ b/drivers/xen/hyper_dmabuf/xen/hyper_dmabuf_xen_comm.c
    @@ -282,6 +282,7 @@ int hyper_dmabuf_xen_init_tx_rbuf(int domid)
    void hyper_dmabuf_xen_cleanup_tx_rbuf(int domid)
    {
    struct xen_comm_tx_ring_info *ring_info;
    + struct xen_comm_rx_ring_info *rx_ring_info;

    /* check if we at all have exporter ring for given rdomain */
    ring_info = xen_comm_find_tx_ring(domid);
    @@ -307,6 +308,12 @@ void hyper_dmabuf_xen_cleanup_tx_rbuf(int domid)
    (unsigned long) ring_info->ring_front.sring);

    kfree(ring_info);
    +
    + rx_ring_info = xen_comm_find_rx_ring(domid);
    + if (!rx_ring_info)
    + return;
    +
    + BACK_RING_INIT(&(rx_ring_info->ring_back), rx_ring_info->ring_back.sring, PAGE_SIZE);
    }

    /* importer needs to know about shared page and port numbers for
    @@ -378,9 +385,8 @@ int hyper_dmabuf_xen_init_rx_rbuf(int domid)

    BACK_RING_INIT(&ring_info->ring_back, sring, PAGE_SIZE);

    - ret = bind_interdomain_evtchn_to_irqhandler(domid, rx_port,
    - back_ring_isr, 0,
    - NULL, (void*)ring_info);
    + ret = bind_interdomain_evtchn_to_irq(domid, rx_port);
    +
    if (ret < 0) {
    return -EINVAL;
    }
    @@ -399,6 +405,10 @@ int hyper_dmabuf_xen_init_rx_rbuf(int domid)
    ret = hyper_dmabuf_xen_init_tx_rbuf(domid);
    }

    + ret = request_irq(ring_info->irq,
    + back_ring_isr, 0,
    + NULL, (void*)ring_info);
    +
    return ret;
    }

    @@ -406,6 +416,7 @@ int hyper_dmabuf_xen_init_rx_rbuf(int domid)
    void hyper_dmabuf_xen_cleanup_rx_rbuf(int domid)
    {
    struct xen_comm_rx_ring_info *ring_info;
    + struct xen_comm_tx_ring_info *tx_ring_info;
    struct page *shared_ring;

    /* check if we have importer ring created for given sdomain */
    @@ -425,6 +436,13 @@ void hyper_dmabuf_xen_cleanup_rx_rbuf(int domid)
    gnttab_free_pages(1, &shared_ring);

    kfree(ring_info);
    +
    + tx_ring_info = xen_comm_find_tx_ring(domid);
    + if (!tx_ring_info)
    + return;
    +
    + SHARED_RING_INIT(tx_ring_info->ring_front.sring);
    + FRONT_RING_INIT(&(tx_ring_info->ring_front), tx_ring_info->ring_front.sring, PAGE_SIZE);
    }

    int hyper_dmabuf_xen_init_comm_env(void)
    --
    2.7.4
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