From: Arnd Bergmann <arnd@arndb.de>
To: Chris Metcalf <cmetcalf@tilera.com>
Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org
Subject: Re: [PATCH 6/6] tilegx network driver: initial support
Date: Sun, 29 Apr 2012 11:15:15 +0000 [thread overview]
Message-ID: <201204291115.16127.arnd@arndb.de> (raw)
In-Reply-To: <4F9C6A0A.5090109@tilera.com>
On Saturday 28 April 2012, Chris Metcalf wrote:
> On 4/13/2012 6:34 AM, Arnd Bergmann wrote:
> > On Thursday 12 April 2012, Chris Metcalf wrote:
> >> On 4/10/2012 6:42 AM, Arnd Bergmann wrote:
> >>> Ok, but please remove tile_net_devs then.
> >>> I think a better abstraction for tile_net_devs_for_channel would be
> >>> some interface that lets you add private data to a channel so when
> >>> you get data from a channel, you can extract that pointer from the driver
> >>> using the channel.
> >> I think what would be clearer is to document how and why we are using this
> >> additional data structure. We do access via both arrays where it is
> >> efficient to do so, so getting rid of either of them doesn't seem right.
>
> In the latest round of changes (to be mailed shortly), we eliminated one of
> the arrays entirely. We now just have an array of net_device pointers
> indexed by channel, which we need since we get packets from the hardware
> and are only given the channel. To get the device, we have to look it up
> in the array.
>
> Since this is now the only array of net_device pointers, I eliminated the
> bychannel*() API I discussed in the previous email, since its use didn't
> seem as compelling any more.
>
> >> Let's keep the "normal" tile_net_devs[] as is, indexed by devno, and make
> >> the tile_net_devs_for_channel[] more abstracted by using the following code:
> > The tile_net_devs still feels dirty. You basically only
> > use it in tile_net_handle_egress_timer(), but there you don't
> > actually take the mutex that protects addition and removal from
> > the array, so it's racy in case of hotplug.
>
> We don't free the net_device structures themselves, so it's safe to do a
> lookup in the array and then dereference the net_device pointer even if we
> are doing an "ifconfig down" in another thread. The only way you could
> imagine the net_device getting structures getting freed was via module
> unload, but it turns out that was pretty broken anyway, so I've just
> removed it altogether in the latest version of the patch. So once you have
> a net_device pointer, it remains valid.
Ok, sounds all good then.
Arnd
next prev parent reply other threads:[~2012-04-29 11:15 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-04 20:39 [PATCH 0/6] arch/tile: provide tilegx networking support Chris Metcalf
2012-04-06 20:42 ` [PATCH 6/6] tilegx network driver: initial support Chris Metcalf
2012-04-09 13:49 ` Arnd Bergmann
2012-04-09 21:30 ` Chris Metcalf
2012-04-10 10:42 ` Arnd Bergmann
2012-04-12 23:23 ` Chris Metcalf
2012-04-13 10:34 ` Arnd Bergmann
2012-04-28 22:07 ` Chris Metcalf
2012-04-04 20:39 ` [PATCH v2 0/6] arch/tile: networking support for tilegx Chris Metcalf
2012-04-06 20:42 ` [PATCH v2 6/6] tilegx network driver: initial support Chris Metcalf
2012-04-30 14:35 ` Arnd Bergmann
2001-09-17 4:00 ` [PATCH v3] " Chris Metcalf
2012-05-03 5:41 ` David Miller
2012-05-03 15:45 ` Chris Metcalf
2012-05-03 17:07 ` David Miller
2012-05-03 17:25 ` Chris Metcalf
2012-05-03 16:41 ` [PATCH v4] " Chris Metcalf
2012-05-04 6:42 ` David Miller
2012-05-09 10:42 ` [PATCH v5] " Chris Metcalf
2012-05-11 13:54 ` Ben Hutchings
2012-05-20 4:42 ` [PATCH v6] " Chris Metcalf
2012-05-20 20:55 ` David Miller
2012-05-23 20:42 ` [PATCH v7] " Chris Metcalf
2012-05-24 4:31 ` David Miller
2012-05-25 14:42 ` [PATCH v8] " Chris Metcalf
2012-06-04 20:12 ` [PATCH v9] " Chris Metcalf
2012-06-06 16:41 ` David Miller
2012-06-06 17:31 ` Eric Dumazet
2012-06-06 17:40 ` Eric Dumazet
2012-06-06 18:36 ` Chris Metcalf
2012-06-06 18:54 ` David Miller
2001-09-17 4:00 ` [PATCH v10] " Chris Metcalf
2012-04-06 20:42 ` Chris Metcalf
2012-06-07 20:39 ` David Miller
2012-06-07 20:44 ` Chris Metcalf
2012-06-07 20:47 ` Chris Metcalf
2012-06-07 20:50 ` Ben Hutchings
2012-06-07 20:52 ` Joe Perches
2012-06-07 20:45 ` Chris Metcalf
2012-06-12 0:03 ` David Miller
2012-06-12 13:14 ` Chris Metcalf
2012-06-06 18:10 ` [PATCH v9] " Eric Dumazet
2012-06-06 18:17 ` David Miller
2012-06-06 18:19 ` Ben Hutchings
2012-05-20 16:35 ` [PATCH v5] " Chris Metcalf
2012-04-29 11:15 ` Arnd Bergmann [this message]
2012-04-15 23:06 ` [PATCH 6/6] " Chris Metcalf
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