linux-kernel - Re: [PATCH 00/27] sparc32: sunset sun4m and sun4d

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Date: Wed, 20 Dec 2023 08:36:36 +0000
From: "Arnd Bergmann" <arnd@...nel.org>
To: "Sam Ravnborg" <sam@...nborg.org>,
 "David S . Miller" <davem@...emloft.net>,
 "Andreas Larsson" <andreas@...sler.com>
Cc: "Helge Deller" <deller@....de>,
 "Alexander Viro" <viro@...iv.linux.org.uk>,
 "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
 "Alan Stern" <stern@...land.harvard.edu>, "Jaroslav Kysela" <perex@...ex.cz>,
 "Takashi Iwai" <tiwai@...e.com>, sparclinux@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
 linux-fbdev@...r.kernel.org, dri-devel@...ts.freedesktop.org,
 linux-sound@...r.kernel.org
Subject: Re: [PATCH 00/27] sparc32: sunset sun4m and sun4d

On Tue, Dec 19, 2023, at 22:03, Sam Ravnborg via B4 Relay wrote:
> TODO before this can be applied:
> - Ack from davem - as he is the principal sparc maintainer
> - Tested-by: preferably on a target or QEMU (see above)
>   I expect bugs as there are some involved changes!
>
> Ideas for the future
> - Apply the most relevant downstream Gaisler patches
>   - The ones introducing CAS should have preference as we then
>     can drop the cmpxchg emulation

One note about the CAS -- as far as I can tell, the absence
of the futex() syscall on sparc32 kernels means that no glibc
from the past decade can work correctly as it now requires futex
for its internal locking, though it does work on sparc64 kernels
in compat32 mode as well as the LEON3 kernel that adds futex
support.

There have been a number of other bugs in sun4m/sun4d support that
ended up making the system unusable during the same timeframe,
I remember sysvipc being broken in native 32-bit mode (but again
not in compat mode) and I think Al Viro has a list of things that
he fixed over the years.

All of these were found through inspection rather than testing,
so there is a good chance that other fatal kernel bugs prevent
testing in qemu, at least until the fixes from Andreas' tree
are included.

       Arnd