Re: [PATCH] LoongArch: Only use SC.Q when supported by the assembler

[Huacai Chen]

On Mon, Mar 9, 2026 at 3:07 PM Thomas Weißschuh
<thomas.weissschuh@xxxxxxxxxxxxx> wrote:
>
> Hi LoongArch maintainers,
>
> On Wed, Feb 25, 2026 at 11:09:39AM +0100, Thomas Weißschuh wrote:
> > The 128-bit atomic cmpxchg implementation uses the SC.Q instruction.
> > Older versions of GNU AS do not support that instruction, erroring out:
> >
> > ERROR:root:{standard input}: Assembler messages:
> > {standard input}:4831: Error: no match insn: sc.q     $t0,$t1,$r14
> > {standard input}:6407: Error: no match insn: sc.q     $t0,$t1,$r23
> > {standard input}:10856: Error: no match insn: sc.q    $t0,$t1,$r14
> > make[4]: *** [../scripts/Makefile.build:289: mm/slub.o] Error 1
> >
> > (Binutils 2.41)
> >
> > Test support for SC.Q in kconfig and disable the atomics if the
> > instruction is not available.
> >
> > Fixes: f0e4b1b6e295 ("LoongArch: Add 128-bit atomic cmpxchg support")
> > Closes: https://lore.kernel.org/lkml/20260216082834-edc51c46-7b7a-4295-8ea5-4d9a3ca2224f@xxxxxxxxxxxxx/
> > Signed-off-by: Thomas Weißschuh <thomas.weissschuh@xxxxxxxxxxxxx>
> > ---
> >  arch/loongarch/Kconfig               | 3 +++
> >  arch/loongarch/include/asm/cmpxchg.h | 5 +++++
> >  2 files changed, 8 insertions(+)
>
> (...)
>
> This is still broken in mainline. Any chance to get this patch to Linus?
Now queued for loongarch-fixes, sorry for the late response.

Huacai

>
>
> Thomas
>