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Message-ID: <ZO4FiJpLSFISkK10@shell.armlinux.org.uk>
Date: Tue, 29 Aug 2023 15:49:44 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Mihai Carabas <mihai.carabas@...cle.com>,
Joao Martins <joao.m.martins@...cle.com>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
"H. Peter Anvin" <hpa@...or.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Wanpeng Li <wanpengli@...cent.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
"Rafael J. Wysocki" <rafael@...nel.org>,
Daniel Lezcano <daniel.lezcano@...aro.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Kees Cook <keescook@...omium.org>,
Petr Mladek <pmladek@...e.com>,
Ard Biesheuvel <ardb@...nel.org>,
Sami Tolvanen <samitolvanen@...gle.com>,
Nicholas Piggin <npiggin@...il.com>,
Juerg Haefliger <juerg.haefliger@...onical.com>,
Mickaël Salaün <mic@...ikod.net>,
Arnd Bergmann <arnd@...db.de>,
Ankur Arora <ankur.a.arora@...cle.com>,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
kvm@...r.kernel.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH 5/7] arm64: Select ARCH_HAS_CPU_RELAX
On Wed, Aug 09, 2023 at 03:49:41PM +0200, Peter Zijlstra wrote:
> On Wed, Aug 09, 2023 at 02:39:39PM +0300, Mihai Carabas wrote:
> > From: Joao Martins <joao.m.martins@...cle.com>
> >
> > cpu_relax() is necessary to allow cpuidle poll-state to be used,
> > so select it from ARM64 kconfig.
> >
> > Signed-off-by: Joao Martins <joao.m.martins@...cle.com>
> > Signed-off-by: Mihai Carabas <mihai.carabas@...cle.com>
> > ---
> > arch/arm64/Kconfig | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> > index 87ade6549790..7c47617b5722 100644
> > --- a/arch/arm64/Kconfig
> > +++ b/arch/arm64/Kconfig
> > @@ -105,6 +105,7 @@ config ARM64
> > select ARCH_WANT_LD_ORPHAN_WARN
> > select ARCH_WANTS_NO_INSTR
> > select ARCH_WANTS_THP_SWAP if ARM64_4K_PAGES
> > + select ARCH_HAS_CPU_RELAX
> > select ARCH_HAS_UBSAN_SANITIZE_ALL
> > select ARM_AMBA
> > select ARM_ARCH_TIMER
>
> Uh what ?! cpu_relax() is assumed present on all archs, no?
I think you have x86 to blame for that!
That symbol is used in drivers/acpi/processor_idle.c to setup stuff
for the cpuidle polling, and also by cpuidle's Makefile to build
poll_state.o
It isn't to do with the presence of cpu_relax() or not.
It probably ought to be renamed to CPUIDLE_CPU_RELAX which would
better describe its modern purpose.
--
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