Re: [PATCH v3 0/8] alpha: enable generic entry infrastructure

[Magnus Lindholm]

On Sun, Jun 14, 2026 at 3:39 AM Michael Cree <mcree@xxxxxxxxxxxx> wrote:
>
> On Fri, Jun 12, 2026 at 10:26:48PM +0200, Magnus Lindholm wrote:
> > This series moves Alpha closer to the common architecture infrastructure
> > and enables GENERIC_ENTRY and GENERIC_IRQ_ENTRY. This is v3 of this patch
> > series, please see below for changes since v1 and v2.
>
> I am seeing sporadic Xorg crashes with this patchset applied to a 7.0
> stable series kernel, usually within a minute of logging into the
> desktop. The rest of system keeps running fine and there are no
> messsages in the kernel log.  I am testing on an XP1000 with Radeon
> HD4350 graphics card.  The same kernel without this patchset works
> fine -- no Xorg crashes.  Indeed, it has been playing the dulcet
> tones of Pink Floyd through my sound system for the last hour without
> a problem.
>
> Example Xorg backtrace follows.  In this case it is a fp exception
> but sometimes it is a segfault:
>

Michael,

Thanks a lot for taking the time to test this series. I was close to sending
a pull request with it, but your testing clearly shows that it still needs
more work, so I will hold off.

Given the symptoms, my first suspicion is that the final generic-entry patch
has changed the Alpha return-to-user/signal path in a way that loses the old
explicit FPU save before signal delivery. The old do_work_pending() path did
a save_fpu() before calling do_signal(), while the new path goes through
arch_do_signal_or_restart() and the generic exit-to-user code. If I missed
preserving that Alpha-specific FPU handling, that could plausibly explain
sporadic SIGFPE/SEGV failures in FP-heavy code such as Xorg/pixman.

I have an XP1000 with a similar Radeon card, so this sounds like something I
should be able to reproduce locally. Unfortunately I do not have access to
that machine right now, so any proper fix will have to wait until the next
merge window.

Thanks again for catching this before I sent the pull request.

Magnus