netdev - Re: [RFC] New driver API to speed up small packets xmits

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Message-ID: <46440D39.8060207@gmail.com>
Date:	Thu, 10 May 2007 23:29:13 -0700
From:	Gagan Arneja <gaagaan@...il.com>
To:	Krishna Kumar2 <krkumar2@...ibm.com>
Cc:	Evgeniy Polyakov <johnpol@....mipt.ru>, netdev@...r.kernel.org,
	Rick Jones <rick.jones2@...com>,
	Sridhar Samudrala <sri@...ibm.com>
Subject: Re: [RFC] New driver API to speed up small packets xmits

Krishna Kumar2 wrote:
>> What about a race between trying to reacquire queue_lock and another
>> failed transmit?
> 
> That is not possible too. I hold the QDISC_RUNNING bit in dev->state and
> am the only sender for this device, so there is no other failed transmit.
> Also, on failure of dev_hard_start_xmit, qdisc_restart will spin for the
> queue lock (which could be held quickly by enqueuer's), and q->requeue()
> skbs to the head of the list.

I have to claim incomplete familiarity for the code. But still, if 
you're out there running with no locks for a period, there's no 
assumption you can make. The "lock could be held quickly" assertion is a 
fallacy.

> 
> Thanks,
> 
> - KK
> 
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