netdev - Re: [PATCH RFX]: napi

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Date:	Sat, 28 Jul 2007 22:30:49 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	rdreier@...co.com
Cc:	netdev@...r.kernel.org, shemminger@...ux-foundation.org,
	rusty@...tcorp.com.au, jgarzik@...ox.com
Subject: Re: [PATCH RFX]: napi_struct V3

From: Roland Dreier <rdreier@...co.com>
Date: Sat, 28 Jul 2007 08:21:58 -0700

>  > Another area of consternation are drivers that were using
>  > netif_rx_reschedule(), as that interface was removed because it
>  > doesn't fit well with the caller managing the dev->quota et al.  I
>  > left race conditions in the drivers that were using that interface,
>  > but they should still basically work nonetheless.
> 
> ...but this is a problem for IPoIB.  The underlying IB stuff only
> allows us to register what is essentially a one-shot edge-triggered
> interrupt.  So there is a race between calling netif_rx_complete() and
> calling ib_req_notify_cq() (which enables the interrupt), since the
> interrupt might never happen if a packet arrives between the two calls.

You will see further along in the thread that we have found
a locking sequence by which this issue can be resolved.

Please read the full thread and the most recent patch before
coming to conclusions :-)
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