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From: Will Deacon <will.deacon@arm.com>
To: Jason Low <jason.low2@hp.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	linux-kernel@vger.kernel.org, mingo@redhat.com,
	paulmck@linux.vnet.ibm.com, terry.rudd@hpe.com,
	waiman.long@hpe.com, boqun.feng@gmail.com, dave@stgolabs.net,
	kbuild test robot <lkp@intel.com>,
	kbuild-all@01.org
Subject: Re: [PATCH v2] MCS spinlock: Use smp_cond_load_acquire()
Date: Wed, 13 Apr 2016 18:43:04 +0100	[thread overview]
Message-ID: <20160413174302.GC21722@arm.com> (raw)
In-Reply-To: <1460516537.2709.7.camel@j-VirtualBox>

On Tue, Apr 12, 2016 at 08:02:17PM -0700, Jason Low wrote:
> For qspinlocks on ARM64, we would like to use WFE instead
> of purely spinning. Qspinlocks internally have lock
> contenders spin on an MCS lock.
> 
> Update arch_mcs_spin_lock_contended() such that it uses
> the new smp_cond_load_acquire() so that ARM64 can also
> override this spin loop with its own implementation using WFE.
> 
> On x86, it can also cheaper to use this than spinning on
> smp_load_acquire().
> 
> Signed-off-by: Jason Low <jason.low2@hp.com>

FWIW, we just override arch_mcs_spin_lock_contended entirely for arch/arm/
and use wfe there so we could do the same for arm64 in mainline already.

Will

  reply	other threads:[~2016-04-13 17:43 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-04-13  3:02 [PATCH v2] MCS spinlock: Use smp_cond_load_acquire() Jason Low
2016-04-13 17:43 ` Will Deacon [this message]
2016-04-13 20:49   ` Jason Low
2016-04-14  8:53     ` Will Deacon

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