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Re: [PATCH net 2/4] hv_netvsc: reset vf_inject on VF removal

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On Thu, 11 Aug 2016 14:09:53 +0200
Vitaly Kuznetsov <vkuznets@redhat.com> wrote:

> Yuval Mintz <Yuval.Mintz@qlogic.com> writes:
> 
> >> +static void netvsc_inject_enable(struct net_device_context
> >> +*net_device_ctx) {
> >> +	net_device_ctx->vf_inject = true;
> >> +}
> >> +
> >> +static void netvsc_inject_disable(struct net_device_context
> >> +*net_device_ctx) {
> >> +	net_device_ctx->vf_inject = false;
> >> +
> >> +	/* Wait for currently active users to drain out. */
> >> +	while (atomic_read(&net_device_ctx->vf_use_cnt) != 0)
> >> +		udelay(50);
> >> +}  
> >
> > That was already the behavior before, but are you certain you
> > want to unconditionally block without any possible timeout?  
> 
> Yes, this is OK. After PATCH4 of this series there is only one place
> which takes the vf_use_cnt (netvsc_recv_callback()) and it is an
> interrupt handler, there are no sleepable operations there.
> 

Since network devices are protected by RCU, it looks like the refcount
is not necessary.  I think vf_inject flag and vf_use_cnt could just be replaced
by doing RCU on vf_netdev.

The callback is invoked from tasklet (softirq) context.

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Thread

[PATCH net 2/4] hv_netvsc: reset vf_inject on VF removal Vitaly Kuznetsov <vkuznets@redhat.com> - 2016-08-11 13:00 +0200
  RE: [PATCH net 2/4] hv_netvsc: reset vf_inject on VF removal Yuval Mintz <Yuval.Mintz@qlogic.com> - 2016-08-11 13:50 +0200
    Re: [PATCH net 2/4] hv_netvsc: reset vf_inject on VF removal Vitaly Kuznetsov <vkuznets@redhat.com> - 2016-08-11 14:20 +0200
      Re: [PATCH net 2/4] hv_netvsc: reset vf_inject on VF removal Stephen Hemminger <stephen@networkplumber.org> - 2016-08-12 16:50 +0200
  Re: [PATCH net 2/4] hv_netvsc: reset vf_inject on VF removal David Miller <davem@davemloft.net> - 2016-08-13 05:50 +0200
  [RFC 2/2] netvsc: use RCU for VF net device reference Stephen Hemminger <stephen@networkplumber.org> - 2016-08-14 13:20 +0200
    Re: [RFC 2/2] netvsc: use RCU for VF net device reference Vitaly Kuznetsov <vkuznets@redhat.com> - 2016-08-15 12:10 +0200
  [RFC 1/2] netvsc: reference counting fix Stephen Hemminger <stephen@networkplumber.org> - 2016-08-14 13:30 +0200
    Re: [RFC 1/2] netvsc: reference counting fix David Miller <davem@davemloft.net> - 2016-08-15 06:40 +0200

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