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@xxxxxxxxxxxxx>
Reviewed-by: K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
---
drivers/net/hyperv/rndis_filter.c | 19 +++++++++++++------
1 files changed, 13 insertions(+), 6 deletions(-)
diff --git a/drivers/net/hyperv/rndis_filter.c b/drivers/net/hyperv/rndis_filter.c
index a37bbda..47d07c5 100644
--- 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);
--
1.7.4.1
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