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

Thomas Weißschuh posted 1 patch 1 month, 1 week ago 
arch/loongarch/Kconfig               | 3 +++
arch/loongarch/include/asm/cmpxchg.h | 5 +++++
2 files changed, 8 insertions(+)
[PATCH] LoongArch: Only use SC.Q when supported by the assembler
Posted by Thomas Weißschuh 1 month, 1 week ago 
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@linutronix.de/
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
---
 arch/loongarch/Kconfig               | 3 +++
 arch/loongarch/include/asm/cmpxchg.h | 5 +++++
 2 files changed, 8 insertions(+)

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index d211c6572b0a..92068ff38685 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -304,6 +304,9 @@ config AS_HAS_LBT_EXTENSION
 config AS_HAS_LVZ_EXTENSION
 	def_bool $(as-instr,hvcl 0)
 
+config AS_HAS_SCQ_EXTENSION
+	def_bool $(as-instr,sc.q \$t0$(comma)\$t1$(comma)\$t2)
+
 config CC_HAS_ANNOTATE_TABLEJUMP
 	def_bool $(cc-option,-mannotate-tablejump)
 
diff --git a/arch/loongarch/include/asm/cmpxchg.h b/arch/loongarch/include/asm/cmpxchg.h
index 58cabab6d90d..909f9274fe71 100644
--- a/arch/loongarch/include/asm/cmpxchg.h
+++ b/arch/loongarch/include/asm/cmpxchg.h
@@ -238,6 +238,8 @@ __cmpxchg(volatile void *ptr, unsigned long old, unsigned long new, unsigned int
 	arch_cmpxchg((ptr), (o), (n));					\
   })
 
+#ifdef CONFIG_AS_HAS_SCQ_EXTENSION
+
 union __u128_halves {
 	u128 full;
 	struct {
@@ -290,6 +292,9 @@ union __u128_halves {
 	BUILD_BUG_ON(sizeof(*(ptr)) != 16);				\
 	__arch_cmpxchg128(ptr, o, n, "");				\
 })
+
+#endif /* CONFIG_AS_HAS_SCQ_EXTENSION */
+
 #else
 #include <asm-generic/cmpxchg-local.h>
 #define arch_cmpxchg64_local(ptr, o, n) __generic_cmpxchg64_local((ptr), (o), (n))

---
base-commit: 2961f841b025fb234860bac26dfb7fa7cb0fb122
change-id: 20260218-loongarch-scq-2434ec5aec4d

Best regards,
-- 
Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Re: [PATCH] LoongArch: Only use SC.Q when supported by the assembler
Posted by Thomas Weißschuh 4 weeks, 1 day ago 
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@linutronix.de/
> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
> ---
>  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?


Thomas
Re: [PATCH] LoongArch: Only use SC.Q when supported by the assembler
Posted by Huacai Chen 4 weeks ago 
On Mon, Mar 9, 2026 at 3:07 PM Thomas Weißschuh
<thomas.weissschuh@linutronix.de> 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@linutronix.de/
> > Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
> > ---
> >  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
>
Re: [PATCH] LoongArch: Only use SC.Q when supported by the assembler
Posted by Hengqi Chen 1 month, 1 week ago 
On Wed, Feb 25, 2026 at 6:09 PM Thomas Weißschuh
<thomas.weissschuh@linutronix.de> 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@linutronix.de/
> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
> ---

Acked-by: Hengqi Chen <hengqi.chen@gmail.com>
Tested-by: Hengqi Chen <hengqi.chen@gmail.com>

>  arch/loongarch/Kconfig               | 3 +++
>  arch/loongarch/include/asm/cmpxchg.h | 5 +++++
>  2 files changed, 8 insertions(+)
>
> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> index d211c6572b0a..92068ff38685 100644
> --- a/arch/loongarch/Kconfig
> +++ b/arch/loongarch/Kconfig
> @@ -304,6 +304,9 @@ config AS_HAS_LBT_EXTENSION
>  config AS_HAS_LVZ_EXTENSION
>         def_bool $(as-instr,hvcl 0)
>
> +config AS_HAS_SCQ_EXTENSION
> +       def_bool $(as-instr,sc.q \$t0$(comma)\$t1$(comma)\$t2)
> +
>  config CC_HAS_ANNOTATE_TABLEJUMP
>         def_bool $(cc-option,-mannotate-tablejump)
>
> diff --git a/arch/loongarch/include/asm/cmpxchg.h b/arch/loongarch/include/asm/cmpxchg.h
> index 58cabab6d90d..909f9274fe71 100644
> --- a/arch/loongarch/include/asm/cmpxchg.h
> +++ b/arch/loongarch/include/asm/cmpxchg.h
> @@ -238,6 +238,8 @@ __cmpxchg(volatile void *ptr, unsigned long old, unsigned long new, unsigned int
>         arch_cmpxchg((ptr), (o), (n));                                  \
>    })
>
> +#ifdef CONFIG_AS_HAS_SCQ_EXTENSION
> +
>  union __u128_halves {
>         u128 full;
>         struct {
> @@ -290,6 +292,9 @@ union __u128_halves {
>         BUILD_BUG_ON(sizeof(*(ptr)) != 16);                             \
>         __arch_cmpxchg128(ptr, o, n, "");                               \
>  })
> +
> +#endif /* CONFIG_AS_HAS_SCQ_EXTENSION */
> +
>  #else
>  #include <asm-generic/cmpxchg-local.h>
>  #define arch_cmpxchg64_local(ptr, o, n) __generic_cmpxchg64_local((ptr), (o), (n))
>
> ---
> base-commit: 2961f841b025fb234860bac26dfb7fa7cb0fb122
> change-id: 20260218-loongarch-scq-2434ec5aec4d
>
> Best regards,
> --
> Thomas Weißschuh <thomas.weissschuh@linutronix.de>
>
Re: [PATCH] LoongArch: Only use SC.Q when supported by the assembler
Posted by Xi Ruoyao 1 month, 1 week ago 
On Wed, 2026-02-25 at 11:09 +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@linutronix.de/
> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>

I have written something similar (only the identifier of the config
entry is different), but I just didn't get the time to set up an old
toolchain and test it.

Reviewed-by: Xi Ruoyao <xry111@xry111.site>

> ---
>  arch/loongarch/Kconfig               | 3 +++
>  arch/loongarch/include/asm/cmpxchg.h | 5 +++++
>  2 files changed, 8 insertions(+)
> 
> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> index d211c6572b0a..92068ff38685 100644
> --- a/arch/loongarch/Kconfig
> +++ b/arch/loongarch/Kconfig
> @@ -304,6 +304,9 @@ config AS_HAS_LBT_EXTENSION
>  config AS_HAS_LVZ_EXTENSION
>  	def_bool $(as-instr,hvcl 0)
>  
> +config AS_HAS_SCQ_EXTENSION
> +	def_bool $(as-instr,sc.q \$t0$(comma)\$t1$(comma)\$t2)
> +
>  config CC_HAS_ANNOTATE_TABLEJUMP
>  	def_bool $(cc-option,-mannotate-tablejump)
>  
> diff --git a/arch/loongarch/include/asm/cmpxchg.h b/arch/loongarch/include/asm/cmpxchg.h
> index 58cabab6d90d..909f9274fe71 100644
> --- a/arch/loongarch/include/asm/cmpxchg.h
> +++ b/arch/loongarch/include/asm/cmpxchg.h
> @@ -238,6 +238,8 @@ __cmpxchg(volatile void *ptr, unsigned long old, unsigned long new, unsigned int
>  	arch_cmpxchg((ptr), (o), (n));					\
>    })
>  
> +#ifdef CONFIG_AS_HAS_SCQ_EXTENSION
> +
>  union __u128_halves {
>  	u128 full;
>  	struct {
> @@ -290,6 +292,9 @@ union __u128_halves {
>  	BUILD_BUG_ON(sizeof(*(ptr)) != 16);				\
>  	__arch_cmpxchg128(ptr, o, n, "");				\
>  })
> +
> +#endif /* CONFIG_AS_HAS_SCQ_EXTENSION */
> +
>  #else
>  #include <asm-generic/cmpxchg-local.h>
>  #define arch_cmpxchg64_local(ptr, o, n) __generic_cmpxchg64_local((ptr), (o), (n))
> 
> ---
> base-commit: 2961f841b025fb234860bac26dfb7fa7cb0fb122
> change-id: 20260218-loongarch-scq-2434ec5aec4d
> 
> Best regards,

-- 
Xi Ruoyao <xry111@xry111.site>

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