From: "Paul E. McKenney" <paulmck@linux•vnet.ibm.com>
To: Michael Ellerman <mpe@ellerman•id.au>
Cc: Ingo Molnar <mingo@kernel•org>,
boqun.feng@linux•vnet.ibm.com, bobby.prani@gmail•com,
peterz@infradead•org, fweisbec@gmail•com, dvhart@linux•intel.com,
jiangshanlai@gmail•com, linux-kernel@vger•kernel.org,
rostedt@goodmis•org, josh@joshtriplett•org, dhowells@redhat•com,
edumazet@google•com, mathieu.desnoyers@efficios•com,
oleg@redhat•com, dipankar@in•ibm.com, will.deacon@arm•com,
akpm@linux-foundation•org, linuxppc-dev@lists•ozlabs.org,
tglx@linutronix•de
Subject: Re: [PATCH tip/core/rcu 2/3] srcu: Force full grace-period ordering
Date: Mon, 23 Jan 2017 18:45:28 -0800 [thread overview]
Message-ID: <20170124024528.GG28085@linux.vnet.ibm.com> (raw)
In-Reply-To: <87efzub3fw.fsf@concordia.ellerman.id.au>
On Mon, Jan 23, 2017 at 07:12:03PM +1100, Michael Ellerman wrote:
> "Paul E. McKenney" <paulmck@linux•vnet.ibm.com> writes:
>
> > On Sat, Jan 14, 2017 at 11:54:17AM -0800, Paul E. McKenney wrote:
> >> On Sat, Jan 14, 2017 at 10:35:50AM +0100, Ingo Molnar wrote:
> >> > * Paul E. McKenney <paulmck@linux•vnet.ibm.com> wrote:
> >
> > [ . . . ]
> >
> >> > > + */
> >> > > +#ifdef CONFIG_PPC
> >> > > +#define smp_mb__after_unlock_lock() smp_mb() /* Full ordering for lock. */
> >> > > +#else /* #ifdef CONFIG_PPC */
> >> > > +#define smp_mb__after_unlock_lock() do { } while (0)
> >> > > +#endif /* #else #ifdef CONFIG_PPC */
> >> >
> >> > Yeah, so I realize that this was pre-existing code, but putting CONFIG_$ARCH
> >> > #ifdefs into generic headers is generally frowned upon.
> >> >
> >> > The canonical approach would be either to define a helper Kconfig variable that
> >> > can be set by PPC (but other architectures don't need to set it), or to expose a
> >> > suitable macro (function) for architectures to define in their barrier.h arch
> >> > header file.
> >>
> >> Very well, I will add a separate commit for this. 4.11 OK?
> >
> > Does the patch below seem reasonable?
> >
> > Thanx, Paul
> >
> > ------------------------------------------------------------------------
> >
> > commit 271c0601237c41a279f975563e13837bace0df03
> > Author: Paul E. McKenney <paulmck@linux•vnet.ibm.com>
> > Date: Sat Jan 14 13:32:50 2017 -0800
> >
> > rcu: Make arch select smp_mb__after_unlock_lock() strength
> >
> > The definition of smp_mb__after_unlock_lock() is currently smp_mb()
> > for CONFIG_PPC and a no-op otherwise. It would be better to instead
> > provide an architecture-selectable Kconfig option, and select the
> > strength of smp_mb__after_unlock_lock() based on that option. This
> > commit therefore creates CONFIG_ARCH_WEAK_RELACQ, has PPC select it,
> > and bases the definition of smp_mb__after_unlock_lock() on this new
> > CONFIG_ARCH_WEAK_RELACQ Kconfig option.
> >
> > Reported-by: Ingo Molnar <mingo@kernel•org>
> > Signed-off-by: Paul E. McKenney <paulmck@linux•vnet.ibm.com>
> > Cc: Peter Zijlstra <peterz@infradead•org>
> > Cc: Will Deacon <will.deacon@arm•com>
> > Cc: Boqun Feng <boqun.feng@linux•vnet.ibm.com>
> > Cc: Benjamin Herrenschmidt <benh@kernel•crashing.org>
> > Cc: Paul Mackerras <paulus@samba•org>
> > Cc: Michael Ellerman <mpe@ellerman•id.au>
> > Cc: <linuxppc-dev@lists•ozlabs.org>
>
> Personally I'd call it ARCH_WEAK_RELEASE_ACQUIRE, which is longer but
> clearer I think. But it's not a big deal, so which ever you prefer.
ARCH_WEAK_RELEASE_ACQUIRE it is!
> Acked-by: Michael Ellerman <mpe@ellerman•id.au>
Applied, thank you!
Thanx, Paul
prev parent reply other threads:[~2017-01-24 2:45 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20170114091941.GA22961@linux.vnet.ibm.com>
[not found] ` <1484385601-23379-2-git-send-email-paulmck@linux.vnet.ibm.com>
[not found] ` <20170114093550.GB14970@gmail.com>
[not found] ` <20170114195417.GW5238@linux.vnet.ibm.com>
2017-01-14 21:41 ` [PATCH tip/core/rcu 2/3] srcu: Force full grace-period ordering Paul E. McKenney
2017-01-15 7:11 ` Ingo Molnar
2017-01-15 7:40 ` Paul E. McKenney
2017-01-15 7:57 ` Ingo Molnar
2017-01-15 9:24 ` Paul E. McKenney
2017-01-15 9:40 ` Ingo Molnar
2017-01-15 19:45 ` Paul E. McKenney
2017-01-16 6:56 ` Ingo Molnar
2017-01-23 8:12 ` Michael Ellerman
2017-01-24 2:45 ` Paul E. McKenney [this message]
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