From: Stanislaw Gruszka <sgruszka@redhat.com>
To: Stephen Hemminger <shemminger@vyatta.com>
Cc: netdev@vger.kernel.org, Andrew Gallatin <gallatin@myri.com>,
Brice Goglin <brice@myri.com>
Subject: Re: [RFC] myri10ge: small rx_done refactoring
Date: Thu, 24 Mar 2011 09:16:21 +0100 [thread overview]
Message-ID: <20110324081621.GA5508@redhat.com> (raw)
In-Reply-To: <20110323083357.457f10aa@nehalam>
On Wed, Mar 23, 2011 at 08:33:57AM -0700, Stephen Hemminger wrote:
> On Wed, 23 Mar 2011 13:52:04 +0100
> Stanislaw Gruszka <sgruszka@redhat.com> wrote:
>
> > Add lro_enable variable to read NETIF_F_LRO flag only once per napi poll
> > call. This should fix theoretical race condition with
> > myri10ge_set_rx_csum() and myri10ge_set_flags() where flag NETIF_F_LRO
> > can be changed.
>
> You may need a barrier or the race may still be there.
I don't understand why barrier in that case is need.
What I tried to avoid is.
myri10ge_clean_rx_done():
if (dev->features & NETIF_F_LRO)
setup lro
myri10ge_set_flags()
if (dev->features & NETIF_F_LRO)
flush lro
Now we read dev->features & NETIF_F_LRO only once to local
lro_enabled variable. So we can not flush without setup
or setup without flush. No idea why memory barries is still
needed.
> The driver seems to use mb() where wmb() is intended, and never use rmb()?
Yes, I think we can have some optimalization here.
Stanislaw
next prev parent reply other threads:[~2011-03-24 8:16 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-23 12:52 [RFC] myri10ge: small rx_done refactoring Stanislaw Gruszka
2011-03-23 15:21 ` Andrew Gallatin
2011-03-23 15:33 ` Stephen Hemminger
2011-03-24 8:16 ` Stanislaw Gruszka [this message]
2011-03-24 15:15 ` Stephen Hemminger
2011-03-24 15:59 ` Stanislaw Gruszka
2011-03-24 16:42 ` Ben Hutchings
2011-03-24 17:29 ` David Howells
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