From: James Bottomley <James.Bottomley@HansenPartnership.com>
To: Chris Metcalf <cmetcalf@tilera.com>
Cc: Jakub Jelinek <jakub@redhat.com>,
One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>,
linux-arch@vger.kernel.org, linux-ia64@vger.kernel.org,
Peter Hurley <peter@hurleysoftware.com>,
Mikael Pettersson <mikpelinux@gmail.com>,
Oleg Nesterov <oleg@redhat.com>,
linux-kernel@vger.kernel.org, Tony Luck <tony.luck@intel.com>,
Paul Mackerras <paulus@samba.org>,
"H. Peter Anvin" <hpa@zytor.com>,
paulmck@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org,
Miroslav Franc <mfranc@redhat.com>,
Richard Henderson <rth@twiddle.net>
Subject: Re: bit fields && data tearing
Date: Mon, 08 Sep 2014 15:43:48 -0700 [thread overview]
Message-ID: <1410216228.2027.88.camel@jarvis.lan> (raw)
In-Reply-To: <540E1587.3060108@tilera.com>
On Mon, 2014-09-08 at 16:45 -0400, Chris Metcalf wrote:
> On 9/8/2014 1:50 AM, James Bottomley wrote:
> > Actual alignment is pretty irrelevant. That's why all architectures
> > which require alignment also have to implement misaligned traps ... this
> > is a fundamental requirement of the networking code, for instance.
>
> Can you clarify what you think the requirement is? The tile architecture
> doesn't support misaligned load/store in general, but we do support it for
> userspace (using a nifty JIT approach with a direct-map hash table kept
> in userspace), and also for get_user/put_user. But that's it, and,
> the networking subsystem works fine for us.
This was years ago (possibly decades). We had to implement in-kernel
unaligned traps for the networking layer because it could access short
and int fields that weren't of the correct alignment when processing
packets. It that's all corrected now, we wouldn't really notice (except
a bit of a speed up since an unaligned trap effectively places the
broken out instructions into the bit stream).
James
> Occasionally we report bugs for driver code that doesn't use the
> get_unaligned_xxx() macros and friends, and our fixes are generally taken
> upstream.
next prev parent reply other threads:[~2014-09-08 22:43 UTC|newest]
Thread overview: 103+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-12 18:13 bit fields && data tearing Oleg Nesterov
2014-07-12 20:51 ` Oleg Nesterov
2014-07-12 23:34 ` Benjamin Herrenschmidt
2014-07-13 12:29 ` Oleg Nesterov
2014-07-13 13:15 ` Peter Hurley
2014-07-13 22:25 ` Benjamin Herrenschmidt
2014-07-15 13:54 ` Peter Hurley
2014-07-15 15:02 ` Richard Henderson
2014-09-03 22:51 ` Peter Hurley
2014-09-03 23:11 ` Benjamin Herrenschmidt
2014-09-04 8:43 ` David Laight
2014-09-04 9:52 ` Benjamin Herrenschmidt
2014-09-04 22:14 ` H. Peter Anvin
2014-09-05 0:59 ` Peter Hurley
2014-09-05 2:08 ` H. Peter Anvin
2014-09-05 15:31 ` Peter Hurley
2014-09-05 15:41 ` H. Peter Anvin
2014-09-08 17:52 ` One Thousand Gnomes
2014-09-08 17:59 ` H. Peter Anvin
2014-09-08 19:17 ` One Thousand Gnomes
2014-09-09 11:18 ` Peter Hurley
2014-09-08 22:47 ` Peter Hurley
2014-09-09 1:59 ` Paul E. McKenney
2014-09-09 11:14 ` Peter Hurley
2014-09-11 10:04 ` One Thousand Gnomes
2014-09-11 16:16 ` Paul E. McKenney
2014-09-11 20:01 ` Peter Hurley
2014-09-14 23:24 ` One Thousand Gnomes
2014-09-22 19:51 ` Paul E. McKenney
2014-09-23 18:19 ` Peter Hurley
2014-09-23 18:39 ` One Thousand Gnomes
2014-09-08 18:13 ` James Bottomley
2014-09-10 20:18 ` H. Peter Anvin
2014-09-10 21:10 ` Rob Landley
2014-09-05 2:08 ` H. Peter Anvin
2014-09-05 8:16 ` Michael Cree
2014-09-05 18:09 ` Paul E. McKenney
2014-09-05 18:31 ` Paul E. McKenney
2014-09-05 19:52 ` Peter Zijlstra
2014-09-05 20:01 ` Peter Hurley
2014-09-05 20:12 ` Peter Zijlstra
2014-09-05 20:15 ` H. Peter Anvin
2014-09-05 20:19 ` Paul E. McKenney
2014-09-05 18:50 ` Peter Hurley
2014-09-05 19:05 ` Paul E. McKenney
2014-09-05 19:24 ` Peter Hurley
2014-09-05 20:09 ` Paul E. McKenney
2014-09-05 19:38 ` Marc Gauthier
2014-09-05 20:14 ` Peter Hurley
2014-09-05 20:34 ` H. Peter Anvin
2014-09-05 20:42 ` Michael Cree
2014-09-05 20:43 ` Paul E. McKenney
2014-09-05 20:48 ` Thomas Gleixner
2014-09-05 21:05 ` Paul E. McKenney
2014-09-05 20:39 ` Michael Cree
2014-09-05 21:12 ` Peter Hurley
2014-09-05 21:27 ` Michael Cree
2014-09-05 20:42 ` Paul E. McKenney
2014-09-04 8:57 ` Mikael Pettersson
2014-09-04 9:09 ` Jakub Jelinek
2014-09-04 12:24 ` Peter Hurley
2014-09-04 12:29 ` Jakub Jelinek
2014-09-04 16:50 ` One Thousand Gnomes
2014-09-04 19:42 ` Peter Hurley
2014-09-04 22:16 ` H. Peter Anvin
2014-09-05 0:17 ` Paul E. McKenney
2014-09-05 1:57 ` Peter Hurley
2014-09-05 2:11 ` James Bottomley
2014-09-05 2:47 ` Peter Hurley
2014-09-05 4:06 ` Paul E. McKenney
2014-09-05 8:30 ` David Laight
2014-09-05 12:31 ` Peter Hurley
2014-09-05 12:37 ` David Laight
2014-09-05 16:17 ` Peter Hurley
2014-09-25 16:12 ` Pavel Machek
2014-09-07 5:07 ` James Bottomley
2014-09-07 16:21 ` Paul E. McKenney
2014-09-07 19:04 ` James Bottomley
2014-09-07 20:41 ` Peter Hurley
2014-09-08 5:50 ` James Bottomley
2014-09-08 20:45 ` Chris Metcalf
2014-09-08 22:43 ` James Bottomley [this message]
2014-09-09 2:27 ` H. Peter Anvin
2014-09-09 8:11 ` Arnd Bergmann
2014-09-08 23:30 ` Peter Hurley
2014-09-09 2:56 ` James Bottomley
2014-09-09 3:20 ` H. Peter Anvin
2014-09-09 4:30 ` H. Peter Anvin
2014-09-09 10:40 ` Peter Hurley
2014-09-10 21:48 ` James Bottomley
2014-09-10 23:50 ` Peter Hurley
2014-09-11 10:23 ` Will Deacon
2014-09-07 23:00 ` Paul E. McKenney
2014-09-07 23:17 ` H. Peter Anvin
2014-09-07 23:36 ` Paul E. McKenney
2014-09-07 23:39 ` H. Peter Anvin
2014-09-08 5:56 ` James Bottomley
2014-09-08 18:12 ` H. Peter Anvin
2014-09-08 19:09 ` James Bottomley
2014-09-08 19:12 ` H. Peter Anvin
2014-09-08 19:12 ` H. Peter Anvin
2014-09-08 22:39 ` James Bottomley
2014-09-09 2:30 ` H. Peter Anvin
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