From mboxrd@z Thu Jan  1 00:00:00 1970
From: Will Deacon <will.deacon@arm.com>
Subject: Re: [PATCH v4 0/3] locking/rwsem: Rwsem rearchitecture part 0
Date: Fri, 15 Feb 2019 18:40:56 +0000
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To: Peter Zijlstra <peterz@infradead.org>
Cc: Waiman Long <longman@redhat.com>, Ingo Molnar <mingo@redhat.com>, Thomas Gleixner <tglx@linutronix.de>, linux-kernel@vger.kernel.org, linux-alpha@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-c6x-dev@linux-c6x.org, uclinux-h8-devel@lists.sourceforge.jp, linux-hexagon@vger.kernel.org, linux-ia64@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, nios2-dev@lists.rocketboards.org, openrisc@lists.librecores.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-um@lists.infradead.org, linux-xtensa@linux-xtensa.org, linux-arch@vger.kernel.org, x86@kernel.org, Arnd Bergmann <arnd@arndb.de>, Borislav Petkov <bp@alien8>

On Thu, Feb 14, 2019 at 11:37:15AM +0100, Peter Zijlstra wrote:
> On Wed, Feb 13, 2019 at 05:00:14PM -0500, Waiman Long wrote:
> > v4:
> >  - Remove rwsem-spinlock.c and make all archs use rwsem-xadd.c.
> > 
> > v3:
> >  - Optimize __down_read_trylock() for the uncontended case as suggested
> >    by Linus.
> > 
> > v2:
> >  - Add patch 2 to optimize __down_read_trylock() as suggested by PeterZ.
> >  - Update performance test data in patch 1.
> > 
> > The goal of this patchset is to remove the architecture specific files
> > for rwsem-xadd to make it easer to add enhancements in the later rwsem
> > patches. It also removes the legacy rwsem-spinlock.c file and make all
> > the architectures use one single implementation of rwsem - rwsem-xadd.c.
> > 
> > Waiman Long (3):
> >   locking/rwsem: Remove arch specific rwsem files
> >   locking/rwsem: Remove rwsem-spinlock.c & use rwsem-xadd.c for all
> >     archs
> >   locking/rwsem: Optimize down_read_trylock()
> 
> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> 
> with the caveat that I'm happy to exchange patch 3 back to my earlier
> suggestion in case Will expesses concerns wrt the ARM64 performance of
> Linus' suggestion.

Right, the current proposal doesn't work well for us, unfortunately. Which
was your earlier suggestion?

Will