netdev - Re: [patch sungem] improved locking

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Message-Id: <1164754644.5350.110.camel@localhost.localdomain>
Date:	Wed, 29 Nov 2006 09:57:24 +1100
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	David Miller <davem@...emloft.net>
Cc:	eric.lemoine@...il.com, netdev@...r.kernel.org
Subject: Re: [patch sungem] improved locking


> This looks mostly fine.
> 
> I was thinking about the lockless stuff, and I wonder if there
> is a clever way you can get it back down to one PIO on the
> GREG_STAT register.
> 
> I think you'd need to have the ->poll() clear gp->status, then
> do a smp_wb(), right before it re-enables interrupts.
> 
> Then in the interrupt handler, you need to find a way to safely
> OR-in any unset bits in gp->status in a race-free manner.

Having it atomic might work at a slightly smaller cost than a lock,
though atomics don't have strong ordering requirements so you'd still
have to be a bit careful.

Ben.


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