[Xen-devel] [RFC PATCH 18/60] hyper_dmabuf: reset comm channel when one end has disconnected.

[Dongwon Kim <dongwon.kim@xxxxxxxxx>]

From: Mateusz Polrola <mateuszx.potrola@xxxxxxxxx>

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@xxxxxxxxx>
---
 .../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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