[v5,4/7] powerpc/qspinlock: Add ARCH_USE_QUEUED_SPINLOCKS_XCHG32

Commit Message

Guo Ren March 28, 2021, 6:30 a.m. UTC

From: Guo Ren <[e-mail]>

We don't have native hw xchg16 instruction, so let qspinlock
generic code to deal with it.

Using the full-word atomic xchg instructions implement xchg16 has
the semantic risk for atomic operations.

This patch cancels the dependency of on qspinlock generic code on
architecture's xchg16.

Signed-off-by: Guo Ren <[e-mail]>
Cc: Michael Ellerman <[e-mail]>
Cc: Benjamin Herrenschmidt <[e-mail]>
Cc: Paul Mackerras <[e-mail]>
---
 arch/powerpc/Kconfig | 1 +
 1 file changed, 1 insertion(+)

Comments

Christophe Leroy March 28, 2021, 11:14 a.m. UTC | #1

Le 28/03/2021 à 08:30, [e-mail] a écrit :
> From: Guo Ren <[e-mail]>
> 
> We don't have native hw xchg16 instruction, so let qspinlock
> generic code to deal with it.

We have lharx/sthcx pair on some versions of powerpc.

See https://patchwork.ozlabs.org/project/linuxppc-dev/patch/[e-mail]/

Christophe

> 
> Using the full-word atomic xchg instructions implement xchg16 has
> the semantic risk for atomic operations.
> 
> This patch cancels the dependency of on qspinlock generic code on
> architecture's xchg16.
> 
> Signed-off-by: Guo Ren <[e-mail]>
> Cc: Michael Ellerman <[e-mail]>
> Cc: Benjamin Herrenschmidt <[e-mail]>
> Cc: Paul Mackerras <[e-mail]>
> ---
>   arch/powerpc/Kconfig | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 386ae12d8523..69ec4ade6521 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -151,6 +151,7 @@ config PPC
>   	select ARCH_USE_CMPXCHG_LOCKREF		if PPC64
>   	select ARCH_USE_QUEUED_RWLOCKS		if PPC_QUEUED_SPINLOCKS
>   	select ARCH_USE_QUEUED_SPINLOCKS	if PPC_QUEUED_SPINLOCKS
> +	select ARCH_USE_QUEUED_SPINLOCKS_XCHG32	if PPC_QUEUED_SPINLOCKS
>   	select ARCH_WANT_IPC_PARSE_VERSION
>   	select ARCH_WANT_IRQS_OFF_ACTIVATE_MM
>   	select ARCH_WANT_LD_ORPHAN_WARN
>

Guo Ren March 28, 2021, 11:36 a.m. UTC | #2

On Sun, Mar 28, 2021 at 7:14 PM Christophe Leroy
<[e-mail]> wrote:
>
>
>
> Le 28/03/2021 à 08:30, [e-mail] a écrit :
> > From: Guo Ren <[e-mail]>
> >
> > We don't have native hw xchg16 instruction, so let qspinlock
> > generic code to deal with it.
>
> We have lharx/sthcx pair on some versions of powerpc.
>
> See https://patchwork.ozlabs.org/project/linuxppc-dev/patch/[e-mail]/
Got it, thx for the information.

>
> Christophe
>
> >
> > Using the full-word atomic xchg instructions implement xchg16 has
> > the semantic risk for atomic operations.
> >
> > This patch cancels the dependency of on qspinlock generic code on
> > architecture's xchg16.
> >
> > Signed-off-by: Guo Ren <[e-mail]>
> > Cc: Michael Ellerman <[e-mail]>
> > Cc: Benjamin Herrenschmidt <[e-mail]>
> > Cc: Paul Mackerras <[e-mail]>
> > ---
> >   arch/powerpc/Kconfig | 1 +
> >   1 file changed, 1 insertion(+)
> >
> > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> > index 386ae12d8523..69ec4ade6521 100644
> > --- a/arch/powerpc/Kconfig
> > +++ b/arch/powerpc/Kconfig
> > @@ -151,6 +151,7 @@ config PPC
> >       select ARCH_USE_CMPXCHG_LOCKREF         if PPC64
> >       select ARCH_USE_QUEUED_RWLOCKS          if PPC_QUEUED_SPINLOCKS
> >       select ARCH_USE_QUEUED_SPINLOCKS        if PPC_QUEUED_SPINLOCKS
> > +     select ARCH_USE_QUEUED_SPINLOCKS_XCHG32 if PPC_QUEUED_SPINLOCKS
> >       select ARCH_WANT_IPC_PARSE_VERSION
> >       select ARCH_WANT_IRQS_OFF_ACTIVATE_MM
> >       select ARCH_WANT_LD_ORPHAN_WARN
> >

Patch

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 386ae12d8523..69ec4ade6521 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -151,6 +151,7 @@  config PPC
 	select ARCH_USE_CMPXCHG_LOCKREF		if PPC64
 	select ARCH_USE_QUEUED_RWLOCKS		if PPC_QUEUED_SPINLOCKS
 	select ARCH_USE_QUEUED_SPINLOCKS	if PPC_QUEUED_SPINLOCKS
+	select ARCH_USE_QUEUED_SPINLOCKS_XCHG32	if PPC_QUEUED_SPINLOCKS
 	select ARCH_WANT_IPC_PARSE_VERSION
 	select ARCH_WANT_IRQS_OFF_ACTIVATE_MM
 	select ARCH_WANT_LD_ORPHAN_WARN