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Date: Thu, 14 Feb 2019 12:12:11 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Subject: Re: [PATCH v4 2/3] locking/rwsem: Remove rwsem-spinlock.c & use
 rwsem-xadd.c for all archs
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On Thu, Feb 14, 2019 at 11:54:47AM +0100, Geert Uytterhoeven wrote:
> On Wed, Feb 13, 2019 at 11:01 PM Waiman Long <longman@redhat.com> wrote:
> > Currently, we have two different implementation of rwsem:
> >  1) CONFIG_RWSEM_GENERIC_SPINLOCK (rwsem-spinlock.c)
> >  2) CONFIG_RWSEM_XCHGADD_ALGORITHM (rwsem-xadd.c)
> >
> > As we are going to use a single generic implementation for rwsem-xadd.c
> > and no architecture-specific code will be needed, there is no point
> > in keeping two different implementations of rwsem. In most cases, the
> > performance of rwsem-spinlock.c will be worse. It also doesn't get all
> > the performance tuning and optimizations that had been implemented in
> > rwsem-xadd.c over the years.
> >
> > For simplication, we are going to remove rwsem-spinlock.c and make all
> > architectures use a single implementation of rwsem - rwsem-xadd.c.
> >
> > All references to RWSEM_GENERIC_SPINLOCK and RWSEM_XCHGADD_ALGORITHM
> > in the code are removed.
> >
> > Suggested-by: Peter Zijlstra <peterz@infradead.org>
> > Signed-off-by: Waiman Long <longman@redhat.com>
> 
> Note that this conflicts with "[PATCH 03/11] kernel/locks: consolidate
> RWSEM_GENERIC_* options"
> https://lore.kernel.org/lkml/20190213174005.28785-4-hch@lst.de/

*sigh*.. of that never was Cc'ed to locking people :/