linux-kernel - Re: [PATCH 1/2] locking/Kconfig: Add INLINE_SPINLOCKS & INLINE

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Message-ID: <20191028155215.GE5576@willie-the-truck>
Date:   Mon, 28 Oct 2019 15:52:16 +0000
From:   Will Deacon <will@...nel.org>
To:     Waiman Long <longman@...hat.com>
Cc:     x86@...nel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Arnd Bergmann <arnd@...db.de>,
        Sebastian Andrzej Siewior <sebastian@...akpoint.cc>,
        Russell King <linux@...linux.org.uk>
Subject: Re: [PATCH 1/2] locking/Kconfig: Add INLINE_SPINLOCKS &
 INLINE_RWLOCKS

[I thought I replied to this already but I can't find any evidence of that.
 Apologies if you receive this twice!]

On Wed, Oct 16, 2019 at 01:20:27PM -0400, Waiman Long wrote:
> Both the arm64 and s390 architectures decide to inline all the spinlock
> and rwlock functions except the read_trylock() and write_trylock()
> functions for arm64. As other architectures are contemplating about
> inlining those locking functions as well, it makes sense to make it
> easier and less error-prone to do this.
> 
> Two new Kconfig options INLINE_SPINLOCKS and INLINE_RWLOCKS and their
> ARCH_* counterparts are now added to streamline this process. The s390
> and arm64's Kconfig files are modified to use the new Kconfig options.
> 
> There is no functional change for s390. For arm64, both read_trylock()
> and write_trylock() are now inlined as well.
> 
> Suggested-by: Arnd Bergmann <arnd@...db.de>
> Signed-off-by: Waiman Long <longman@...hat.com>
> ---
>  arch/arm64/Kconfig   | 28 ++-------------------------
>  arch/s390/Kconfig    | 30 ++---------------------------
>  kernel/Kconfig.locks | 45 +++++++++++++++++++++++++++++++++++++++++++-
>  3 files changed, 48 insertions(+), 55 deletions(-)
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 950a56b71ff0..e440d85dd8f1 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -35,32 +35,8 @@ config ARM64
>  	select ARCH_HAS_TEARDOWN_DMA_OPS if IOMMU_SUPPORT
>  	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
>  	select ARCH_HAVE_NMI_SAFE_CMPXCHG
> -	select ARCH_INLINE_READ_LOCK if !PREEMPT
> -	select ARCH_INLINE_READ_LOCK_BH if !PREEMPT
> -	select ARCH_INLINE_READ_LOCK_IRQ if !PREEMPT
> -	select ARCH_INLINE_READ_LOCK_IRQSAVE if !PREEMPT
> -	select ARCH_INLINE_READ_UNLOCK if !PREEMPT
> -	select ARCH_INLINE_READ_UNLOCK_BH if !PREEMPT
> -	select ARCH_INLINE_READ_UNLOCK_IRQ if !PREEMPT
> -	select ARCH_INLINE_READ_UNLOCK_IRQRESTORE if !PREEMPT
> -	select ARCH_INLINE_WRITE_LOCK if !PREEMPT
> -	select ARCH_INLINE_WRITE_LOCK_BH if !PREEMPT
> -	select ARCH_INLINE_WRITE_LOCK_IRQ if !PREEMPT
> -	select ARCH_INLINE_WRITE_LOCK_IRQSAVE if !PREEMPT
> -	select ARCH_INLINE_WRITE_UNLOCK if !PREEMPT
> -	select ARCH_INLINE_WRITE_UNLOCK_BH if !PREEMPT
> -	select ARCH_INLINE_WRITE_UNLOCK_IRQ if !PREEMPT
> -	select ARCH_INLINE_WRITE_UNLOCK_IRQRESTORE if !PREEMPT
> -	select ARCH_INLINE_SPIN_TRYLOCK if !PREEMPT
> -	select ARCH_INLINE_SPIN_TRYLOCK_BH if !PREEMPT
> -	select ARCH_INLINE_SPIN_LOCK if !PREEMPT
> -	select ARCH_INLINE_SPIN_LOCK_BH if !PREEMPT
> -	select ARCH_INLINE_SPIN_LOCK_IRQ if !PREEMPT
> -	select ARCH_INLINE_SPIN_LOCK_IRQSAVE if !PREEMPT
> -	select ARCH_INLINE_SPIN_UNLOCK if !PREEMPT
> -	select ARCH_INLINE_SPIN_UNLOCK_BH if !PREEMPT
> -	select ARCH_INLINE_SPIN_UNLOCK_IRQ if !PREEMPT
> -	select ARCH_INLINE_SPIN_UNLOCK_IRQRESTORE if !PREEMPT
> +	select ARCH_INLINE_RWLOCKS if !PREEMPT

This is a change in behaviour, since you're now selecting both
ARCH_INLINE_READ_TRYLOCK and ARCH_INLINE_WRITE_TRYLOCK for arm64.

However, I /think/ that's probably just because I missed that when
enabling the others, so cautiously:

Acked-by: Will Deacon <will@...nel.org> # arm64

Will