From: Will Deacon <will.deacon@arm.com>
To: Ingo Molnar <mingo@kernel.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
mark.rutland@arm.com, snitzer@redhat.com,
thor.thayer@linux.intel.com, viro@zeniv.linux.org.uk,
davem@davemloft.net, shuah@kernel.org, mpe@ellerman.id.au,
tj@kernel.org, torvalds@linux-foundation.org
Subject: Re: [PATCH 17/19] locking/barriers: Kill lockless_dereference
Date: Tue, 24 Oct 2017 10:44:35 +0100 [thread overview]
Message-ID: <20171024094435.GC17909@arm.com> (raw)
In-Reply-To: <20171024093104.rukpl26fukj7bxvg@gmail.com>
On Tue, Oct 24, 2017 at 11:31:04AM +0200, Ingo Molnar wrote:
>
> * Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote:
>
> > From: Will Deacon <will.deacon@arm.com>
> >
> > lockless_dereference is a nice idea, but its gained little traction in
> > kernel code since it's introduction three years ago. This is partly
>
> s/its/it
> s/it's/its
Crikey, no idea what happened there!
> > because it's a pain to type, but also because using READ_ONCE instead
> > will work correctly on all architectures apart from Alpha, which is a
> > fully supported but somewhat niche architecture these days.
> >
> > This patch moves smp_read_barrier_depends() (a NOP on all architectures
> > other than Alpha) from lockless_dereference into READ_ONCE, converts
> > the few actual users over to READ_ONCE and then finally removes
> > lockless_dereference altogether.
>
> Nit: if we refer to smp_read_barrier_depends() with parentheses (which is the nice
> thing to do for function-alike symbols), then we should do the same with
> READ_ONCE() and lockless_dereference() as well.
>
> Also, could we please split this into three patches:
>
> #1: Add smp_read_barrier_depends() to READ_ONCE()
> #2: Convert all lockless_dereference() users to READ_ONCE()
> #3: Remove the now unused lockless_dereference() API
>
> to make it easier to analyze if bisected to, should any problems arise?
Sure, I'll do that now.
Will
next prev parent reply other threads:[~2017-10-24 9:44 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-23 21:04 [GIT PULL de-alpha] Make core code not need to know about Alpha for v4.15 Paul E. McKenney
2017-10-23 21:07 ` [PATCH 01/19] dm integrity: Kill off ACCESS_ONCE() Paul E. McKenney
2017-10-23 21:07 ` Paul E. McKenney
2017-10-23 21:07 ` [PATCH 02/19] EDAC, altera: " Paul E. McKenney
2017-10-23 21:07 ` Paul E. McKenney
2017-10-23 21:07 ` [PATCH 03/19] firmware/ivc: " Paul E. McKenney
2017-10-23 21:07 ` Paul E. McKenney
2017-10-23 21:07 ` [PATCH 04/19] fs: dcache: " Paul E. McKenney
2017-10-23 21:07 ` Paul E. McKenney
2017-10-23 21:07 ` [PATCH 05/19] fs: ncpfs: " Paul E. McKenney
2017-10-23 21:07 ` [PATCH 06/19] media: dvb_ringbuffer: " Paul E. McKenney
2017-10-23 21:07 ` Paul E. McKenney
2017-10-23 21:07 ` [PATCH 07/19] net: netlink/netfilter: " Paul E. McKenney
2017-10-23 21:07 ` [PATCH 08/19] net/ipv4/tcp_input.c: " Paul E. McKenney
2017-10-23 21:07 ` Paul E. McKenney
2017-10-23 21:07 ` [PATCH 09/19] net: average: " Paul E. McKenney
2017-10-24 5:58 ` Johannes Berg
2017-10-24 5:58 ` Johannes Berg
2017-10-24 9:34 ` Ingo Molnar
2017-10-24 9:34 ` Ingo Molnar
2017-10-24 13:49 ` Paul E. McKenney
2017-10-23 21:07 ` [PATCH 10/19] samples: mic/mpssd/mpssd.c: " Paul E. McKenney
2017-10-23 21:07 ` [PATCH 11/19] selftests/powerpc: " Paul E. McKenney
2017-10-23 21:07 ` Paul E. McKenney
2017-10-23 21:07 ` [PATCH 12/19] workqueue: " Paul E. McKenney
2017-10-23 21:07 ` [PATCH 13/19] rcutorture: formal: Prepare for ACCESS_ONCE() removal Paul E. McKenney
2017-10-23 21:07 ` [PATCH 14/19] doc: filesystems: Kill off ACCESS_ONCE() Paul E. McKenney
2017-10-23 21:07 ` [PATCH 15/19] mm: " Paul E. McKenney
2017-10-23 21:07 ` [PATCH 16/19] linux/compiler.h: Split into compiler.h and compiler-types.h Paul E. McKenney
2017-10-23 21:07 ` Paul E. McKenney
2017-10-24 9:25 ` Ingo Molnar
2017-10-24 9:30 ` Will Deacon
2017-10-24 9:30 ` Will Deacon
2017-10-24 9:52 ` Ingo Molnar
2017-10-24 9:52 ` Ingo Molnar
2017-10-23 21:07 ` [PATCH 17/19] locking/barriers: Kill lockless_dereference Paul E. McKenney
2017-10-23 21:07 ` Paul E. McKenney
2017-10-24 9:31 ` Ingo Molnar
2017-10-24 9:31 ` Ingo Molnar
2017-10-24 9:44 ` Will Deacon [this message]
2017-10-24 9:44 ` Will Deacon
2017-10-24 9:54 ` Ingo Molnar
2017-10-24 9:54 ` Ingo Molnar
2017-10-24 10:23 ` Will Deacon
2017-10-23 21:07 ` [PATCH 18/19] alpha: atomics: Add smp_read_barrier_depends() to release/relaxed atomics Paul E. McKenney
2017-10-23 21:07 ` [PATCH 19/19] COCCINELLE: treewide: kill off ACCESS_ONCE() Paul E. McKenney
2017-10-24 9:32 ` [GIT PULL de-alpha] Make core code not need to know about Alpha for v4.15 Ingo Molnar
2017-10-24 9:32 ` Ingo Molnar
2017-10-25 8:45 ` Ingo Molnar
2017-10-25 8:54 ` Paul E. McKenney
2017-10-25 9:04 ` Ingo Molnar
2017-10-25 9:04 ` Ingo Molnar
2017-10-25 13:18 ` Paul E. McKenney
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