From: Linus Torvalds <torvalds@linux-foundation.org>
To: "Maciej W. Rozycki" <macro@orcam.me.uk>
Cc: Arnd Bergmann <arnd@arndb.de>,
"Paul E. McKenney" <paulmck@kernel.org>,
John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>,
Arnd Bergmann <arnd@kernel.org>,
linux-alpha@vger.kernel.org,
Richard Henderson <richard.henderson@linaro.org>,
Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
Matt Turner <mattst88@gmail.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Marc Zyngier <maz@kernel.org>,
linux-kernel@vger.kernel.org, Michael Cree <mcree@orcon.net.nz>,
Frank Scheiner <frank.scheiner@web.de>
Subject: Re: [PATCH 00/14] alpha: cleanups for 6.10
Date: Mon, 1 Jul 2024 18:13:57 -0700 [thread overview]
Message-ID: <CAHk-=wihNu+_bGwD8F107ds7Lv1Z6ODTwvYYvXeW3im1=4R65w@mail.gmail.com> (raw)
In-Reply-To: <alpine.DEB.2.21.2406302009480.43454@angie.orcam.me.uk>
On Mon, 1 Jul 2024 at 16:48, Maciej W. Rozycki <macro@orcam.me.uk> wrote:
>
> Looking from today's perspective it was clearly a bad choice. However it
> was 30+ years ago, it wasn't so certain as it is now that x86 was there to
> stay
No.
The thing is, it was objectively the wrong thing to do even 30 years
ago, and has nothing to do with x86.
The lack of byte operations literally means that even _word_
operations aren't reliable.
Because when you emulate byte operations with quad-word operations -
which is the way the alpha instruction set was literally designed -
you mess with the adjacent word too.
So even word accesses aren't safe. And I'm pretty sure that
'sig_atomic_t' was just 32-bit on alpha (that's what glibc had, and
I'm pretty sure OSF/1 did too). So...
And that's an issue even just UP, and just completely bog-standard
POSIX 1003.1 and C.
You really can't get much more basic than that.
So supposedly portable programs would have subtle bugs because the
architecture was bad, and the workarounds for that badness were
incomplete.
SMP and IO - which are a thing, and which were things that the
architecture was allegedly designed for - are then only much worse.
The architecture was wrong 30 years ago. It's not that it "became"
wrong in hindsight. It was wrong originally, and it's just that people
hadn't thought things through enough to realize how wrong it was.
The only way it's not wrong is if you say "byte accesses do not
matter". That's a very Cray way of looking at things - Cray 1 had a
64-bit "char" in C, because there were no byte accesses.
That's fine if your only goal in life is to do HPC.
So if you simply don't care about bytes, and you *only* work with
words and quad-words, then alpha looks ok.
But honestly, that's basically saying "in a different universe, alpha
is not a mis-design".
That's not the universe we live in, and it's entirely unrelated to
x86. Bytes were very much a thing 30 years ago, and they will be a
thing 30 years from now even if x86 is dead and buried.
Basically, the fundamental mistake of thinking that you can do byte
operations by just masking quad-words screwed up POSIX compatibility,
screwed up SMP, and majorly screwed up the alpha IO layer too.
And by the time it was fixed, it was too late.
Don't make excuses for it. It's not ok today, but it really wasn't ok
30 years ago either.
It's ok to have rose-colored glasses and have a weak spot in your
heart for an architecture. But let's not make that weak spot in your
heart be a weak spot in your mind.
Linus
next prev parent reply other threads:[~2024-07-02 1:14 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-03 8:11 [PATCH 00/14] alpha: cleanups for 6.10 Arnd Bergmann
2024-05-03 8:11 ` [PATCH 01/14] alpha: sort scr_mem{cpy,move}w() out Arnd Bergmann
2024-05-03 8:11 ` [PATCH 02/14] alpha: fix modversions for strcpy() et.al Arnd Bergmann
2024-05-03 8:11 ` [PATCH 03/14] alpha: add clone3() support Arnd Bergmann
2024-05-03 8:11 ` [PATCH 04/14] alpha: don't make functions public without a reason Arnd Bergmann
2024-05-03 8:11 ` [PATCH 05/14] alpha: sys_sio: fix misspelled ifdefs Arnd Bergmann
2024-05-03 8:11 ` [PATCH 06/14] alpha: missing includes Arnd Bergmann
2024-05-03 8:11 ` [PATCH 07/14] alpha: core_lca: take the unused functions out Arnd Bergmann
2024-05-03 8:11 ` [PATCH 08/14] alpha: jensen, t2 - make __EXTERN_INLINE same as for the rest Arnd Bergmann
2024-05-03 8:11 ` [PATCH 09/14] alpha: trim the unused stuff from asm-offsets.c Arnd Bergmann
2024-05-03 8:11 ` [PATCH 10/14] alpha: remove DECpc AXP150 (Jensen) support Arnd Bergmann
2024-05-03 16:07 ` Linus Torvalds
2024-05-03 17:00 ` Al Viro
2024-05-03 20:07 ` Arnd Bergmann
2024-05-03 8:11 ` [PATCH 11/14] alpha: sable: remove early machine support Arnd Bergmann
2024-05-03 8:11 ` [PATCH 12/14] alpha: remove LCA and APECS based machines Arnd Bergmann
2024-05-03 8:11 ` [PATCH 13/14] alpha: cabriolet: remove EV5 CPU support Arnd Bergmann
2024-05-03 8:11 ` [PATCH 14/14] alpha: drop pre-EV56 support Arnd Bergmann
2024-05-04 15:00 ` Richard Henderson
2024-05-06 10:06 ` Arnd Bergmann
2024-06-03 6:02 ` Jiri Slaby
2024-06-04 13:58 ` Greg KH
2024-05-03 16:06 ` [PATCH 00/14] alpha: cleanups for 6.10 Matt Turner
2024-05-03 20:15 ` Arnd Bergmann
2024-05-06 9:16 ` Michael Cree
2024-05-06 10:11 ` Arnd Bergmann
2024-05-03 16:53 ` John Paul Adrian Glaubitz
2024-05-03 17:19 ` Paul E. McKenney
2024-05-27 23:49 ` Maciej W. Rozycki
2024-05-28 14:43 ` Paul E. McKenney
2024-05-29 18:50 ` Maciej W. Rozycki
2024-05-29 22:09 ` Paul E. McKenney
2024-05-30 22:59 ` Maciej W. Rozycki
2024-05-31 3:56 ` Maciej W. Rozycki
2024-05-31 19:33 ` Paul E. McKenney
2024-06-03 16:22 ` Maciej W. Rozycki
2024-06-03 17:08 ` Paul E. McKenney
2024-07-01 23:50 ` Maciej W. Rozycki
2024-05-30 1:08 ` Linus Torvalds
2024-05-30 22:57 ` Maciej W. Rozycki
2024-05-31 0:10 ` Linus Torvalds
2024-06-03 11:09 ` Maciej W. Rozycki
2024-06-03 11:36 ` John Paul Adrian Glaubitz
2024-06-03 16:57 ` Linus Torvalds
2024-07-01 23:48 ` Maciej W. Rozycki
2024-05-31 15:48 ` Arnd Bergmann
2024-05-31 16:32 ` Linus Torvalds
2024-05-31 16:54 ` Arnd Bergmann
2024-06-01 13:51 ` David Laight
2024-07-01 23:48 ` Maciej W. Rozycki
2024-07-02 1:13 ` Linus Torvalds [this message]
2024-07-03 0:12 ` Maciej W. Rozycki
2024-07-03 0:50 ` Linus Torvalds
2024-07-04 22:21 ` Maciej W. Rozycki
2024-06-03 11:33 ` Maciej W. Rozycki
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