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Re: [PATCH]: was Re: LLTX and netif_stop_queue

To: "David S. Miller" <davem@xxxxxxxxxxxxx>
Subject: Re: [PATCH]: was Re: LLTX and netif_stop_queue
From: Andi Kleen <ak@xxxxxxx>
Date: Thu, 27 Jan 2005 09:26:18 +0100
Cc: Andi Kleen <ak@xxxxxxx>, buytenh@xxxxxxxxxxxxxx, shemminger@xxxxxxxx, roland@xxxxxxxxxxx, hadi@xxxxxxxxxx, iod00d@xxxxxx, eric.lemoine@xxxxxxxxx, netdev@xxxxxxxxxxx, openib-general@xxxxxxxxxx, kaber@xxxxxxxxx
In-reply-to: <20050126232227.3ce4decb.davem@davemloft.net>
References: <20050119164640.6c67bdfa.davem@davemloft.net> <52r7kgu5n5.fsf@topspin.com> <20050119230526.393a5184.davem@davemloft.net> <20050120085611.33f9485e@dxpl.pdx.osdl.net> <20050121105452.GA12988@xi.wantstofly.org> <20050125222705.1ee878fd.davem@davemloft.net> <20050126132512.GA18220@xi.wantstofly.org> <20050126223247.3e4643cc.davem@davemloft.net> <20050127071645.GA2731@wotan.suse.de> <20050126232227.3ce4decb.davem@davemloft.net>
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On Wed, Jan 26, 2005 at 11:22:27PM -0800, David S. Miller wrote:
> On Thu, 27 Jan 2005 08:16:45 +0100
> Andi Kleen <ak@xxxxxxx> wrote:
> 
> > > Yes, that's the idea.
> > 
> > per CPU only works in preemptive kernel if you have preemption
> > disabled all the time. Do you? 
> > 
> > Seems not likely to me.
> 
> BH is disabled in these code paths (specifically we're talking
> about ->hard_start_xmit()), as that is where the recursion
> check goes.

Hmm, but hard_start_xmit is allowed to enable preemption again, isn't it?

An safer alternative may be to change the cpu mask of the current process
temporarily.

-Andi

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