Re: [PATCH] ARM: add get_user() support for 8 byte types - Russell King

From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
Cc: Arnd Bergmann <arnd@arndb.de>, Rob Clark <rob.clark@linaro.org>,
	patches@linaro.org, linux-kernel@vger.kernel.org,
	dri-devel@lists.freedesktop.org, linux-omap@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	Jamie Lokier <jamie@shareable.org>
Subject: Re: [PATCH] ARM: add get_user() support for 8 byte types
Date: Mon, 19 Nov 2012 14:48:06 +0000	[thread overview]
Message-ID: <20121119144806.GO3332@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <20121119143236.GA3296@intel.com>

On Mon, Nov 19, 2012 at 04:32:36PM +0200, Ville Syrjälä wrote:
> On Thu, Nov 15, 2012 at 02:39:41PM +0000, Arnd Bergmann wrote:
> > On Thursday 15 November 2012, Rob Clark wrote:
> > > > I still haven't heard a conclusive argument why we need to use get_user()
> > > > rather than copy_from_user() in the DRM code. Is this about a fast path
> > > > where you want to shave off a few cycles for each call, or does this
> > > > simplify the code structure, or something else?
> > > 
> > > well, it is mostly because it seemed like a good idea to first try to
> > > solve the root issue, rather than having to fix things up in each
> > > driver when someone from x86-world introduces a 64b get_user()..
> > 
> > As pointed out by hpa earlier, x86-32 doesn't have a 64b get_user
> > either. I don't think we have a lot of drivers that are used only
> > on 64-bit x86 and on 32-bit ARM but not on 32-bit x86.
> 
> Ouch. I didn't realize that x86-32 doesn't have it. All the systems
> where I've run the new code are 64bit so I never noticed the problem.
> 
> I see there was a patch [1] posted a long time ago to implement 64bit
> get_user() on x86-32. I wonder what happened to it?
> 
> [1] https://lkml.org/lkml/2004/4/20/96

Wonderful lkml.org after four "Negotiating SSL connection..." messages
gives me under elinks...

	Unable to retrieve https://lkml.org/lkml/2004/4/20/96:
			Error reading from socket

and with wget:

$ wget https://lkml.org/lkml/2004/4/20/96
--2012-11-19 14:47:16--  https://lkml.org/lkml/2004/4/20/96
Resolving lkml.org... 87.253.128.182
Connecting to lkml.org|87.253.128.182|:443... connected.
HTTP request sent, awaiting response... No data received.
Retrying.

--2012-11-19 14:47:19--  (try: 2)  https://lkml.org/lkml/2004/4/20/96
Connecting to lkml.org|87.253.128.182|:443... connected.
HTTP request sent, awaiting response... No data received.
Retrying.

--2012-11-19 14:47:22--  (try: 3)  https://lkml.org/lkml/2004/4/20/96
Connecting to lkml.org|87.253.128.182|:443... connected.
HTTP request sent, awaiting response... No data received.
Retrying.

--2012-11-19 14:47:26--  (try: 4)  https://lkml.org/lkml/2004/4/20/96
Connecting to lkml.org|87.253.128.182|:443... connected.
HTTP request sent, awaiting response... No data received.
Retrying.
...

what a wonderful site... please choose another LKML archive, preferably
one which works.  Thanks.