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Re: netdev ioctl & dev_base_lock : bad idea ?

To: "David S. Miller" <davem@xxxxxxxxxxxxx>
Subject: Re: netdev ioctl & dev_base_lock : bad idea ?
From: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Date: Thu, 09 Dec 2004 17:22:13 +1100
Cc: netdev@xxxxxxxxxxx
In-reply-to: <20041208220642.6984519f.davem@davemloft.net>
References: <1101458929.28048.9.camel@gaston> <20041208220642.6984519f.davem@davemloft.net>
Sender: netdev-bounce@xxxxxxxxxxx
On Wed, 2004-12-08 at 22:06 -0800, David S. Miller wrote:
> On Fri, 26 Nov 2004 19:48:49 +1100
> Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> wrote:
> 
> > I suppose there is a good reason we can't just use the rtnl_sem for
> > these guys, though why isn't dev_base_lock a read/write semaphore
> > instead of a spinlock ? At least on ppc, I don't think there's any
> > overhead in the normal path, and this is not on a very critical path
> > anyway, is it ?
> 
> It can't be a semphore because it is taken in packet processing,
> and thus softint handling, paths.

Right, and I missed the fact that we did indeed take the semaphore and
not the lock in the _set_ functions which is just fine, we can actually
schedule.... except in set_multicast...

Is there any reason we actually _need_ to get the xmit lock in this one
specifically ?

Ben.



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