hv_netvsc: Move subchannel waiting to rndis_filter_device_remove()

During hot add, vmbus_device_register() is called from vmbus_onoffer(), on
the same workqueue as the subchannel offer message work-queue, so
subchannel offer won't be processed until the vmbus_device_register()/...
/netvsc_probe() is done.
Also, vmbus_device_register() is called with channel_mutex locked, which
prevents subchannel processing too. So the "waiting for sub-channel
processing" will not success in hot add case. But, in usual module loading,
the netvsc_probe() is called from different code path, and doesn't fail.

This patch resolves the deadlock during NIC hot-add, and speeds up NIC
loading time.

Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Reviewed-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/hyperv/rndis_filter.c b/drivers/net/hyperv/rndis_filter.c
index a37bbda37ffa628cf7752e41a4d68d69f3c9e331..47d07c576a344ae144a78ec5064e7091eadbfa24 100644 (file)
--- a/drivers/net/hyperv/rndis_filter.c
+++ b/drivers/net/hyperv/rndis_filter.c
@@ -1175,22 +1175,18 @@ int rndis_filter_device_add(struct hv_device *dev,
        ret = rndis_filter_set_rss_param(rndis_device, net_device->num_chn);
 
        /*
-        * Wait for the host to send us the sub-channel offers.
+        * Set the number of sub-channels to be received.
         */
        spin_lock_irqsave(&net_device->sc_lock, flags);
        sc_delta = num_rss_qs - (net_device->num_chn - 1);
        net_device->num_sc_offered -= sc_delta;
        spin_unlock_irqrestore(&net_device->sc_lock, flags);
 
-       while (net_device->num_sc_offered != 0) {
-               t = wait_for_completion_timeout(&net_device->channel_init_wait, 10*HZ);
-               if (t == 0)
-                       WARN(1, "Netvsc: Waiting for sub-channel processing");
-       }
 out:
        if (ret) {
                net_device->max_chn = 1;
                net_device->num_chn = 1;
+               net_device->num_sc_offered = 0;
        }
 
        return 0; /* return 0 because primary channel can be used alone */
@@ -1204,6 +1200,17 @@ void rndis_filter_device_remove(struct hv_device *dev)
 {
        struct netvsc_device *net_dev = hv_get_drvdata(dev);
        struct rndis_device *rndis_dev = net_dev->extension;
+       unsigned long t;
+
+       /* If not all subchannel offers are complete, wait for them until
+        * completion to avoid race.
+        */
+       while (net_dev->num_sc_offered > 0) {
+               t = wait_for_completion_timeout(&net_dev->channel_init_wait,
+                                               10 * HZ);
+               if (t == 0)
+                       WARN(1, "Netvsc: Waiting for sub-channel processing");
+       }
 
        /* Halt and release the rndis device */
        rndis_filter_halt_device(rndis_dev);