From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org, mingo@kernel.org,
laijs@cn.fujitsu.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de,
rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
darren@dvhart.com, fweisbec@gmail.com, sbw@mit.edu,
Linux-Arch <linux-arch@vger.kernel.org>,
Ingo Molnar <mingo@redhat.com>, Oleg Nesterov <oleg@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
benh@kernel.crashing.org
Subject: Re: [PATCH v5 tip/core/locking 6/7] locking: Add an smp_mb__after_unlock_lock() for UNLOCK+LOCK barrier
Date: Tue, 10 Dec 2013 09:17:18 -0800 [thread overview]
Message-ID: <20131210171718.GS4208@linux.vnet.ibm.com> (raw)
In-Reply-To: <20131210123726.GE13532@twins.programming.kicks-ass.net>
On Tue, Dec 10, 2013 at 01:37:26PM +0100, Peter Zijlstra wrote:
> On Mon, Dec 09, 2013 at 05:28:02PM -0800, Paul E. McKenney wrote:
> > diff --git a/arch/powerpc/include/asm/barrier.h b/arch/powerpc/include/asm/barrier.h
> > index f89da808ce31..abf645799991 100644
> > --- a/arch/powerpc/include/asm/barrier.h
> > +++ b/arch/powerpc/include/asm/barrier.h
> > @@ -84,4 +84,6 @@ do { \
> > ___p1; \
> > })
> >
> > +#define smp_mb__after_unlock_lock() do { } while (0)
> > +
> > #endif /* _ASM_POWERPC_BARRIER_H */
>
> Didn't ben said ppc actually violates the current unlock+lock assumtion
> and therefore this barrier woulnd't actually be a nop on ppc
Last I knew, I was saying that it did in theory, but wasn't able to
demonstrate it in practice. But yes, I would be more comfortable with
it being smp_mb().
Ben?
Thanx, Paul
next prev parent reply other threads:[~2013-12-10 17:17 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-10 1:27 [PATCH v5 tip/core/locking] Memory-barrier documentation updates + smp_mb__after_unlock_lock() Paul E. McKenney
2013-12-10 1:27 ` [PATCH v5 tip/core/locking 1/7] Documentation/memory-barriers.txt: Add needed ACCESS_ONCE() calls to memory-barriers.txt Paul E. McKenney
2013-12-10 1:27 ` [PATCH v5 tip/core/locking 2/7] Documentation/memory-barriers.txt: Add long atomic examples " Paul E. McKenney
2013-12-10 1:27 ` [PATCH v5 tip/core/locking 3/7] Documentation/memory-barriers.txt: Prohibit speculative writes Paul E. McKenney
2013-12-10 1:28 ` [PATCH v5 tip/core/locking 4/7] Documentation/memory-barriers.txt: Document ACCESS_ONCE() Paul E. McKenney
2013-12-10 1:28 ` [PATCH v5 tip/core/locking 5/7] Documentation/memory-barriers.txt: Downgrade UNLOCK+LOCK Paul E. McKenney
2013-12-10 1:32 ` Josh Triplett
2013-12-10 5:19 ` Paul E. McKenney
2013-12-10 13:14 ` Peter Zijlstra
2013-12-10 17:12 ` Paul E. McKenney
2013-12-10 17:25 ` Peter Zijlstra
2013-12-10 17:43 ` Josh Triplett
2013-12-10 18:05 ` Paul E. McKenney
2013-12-10 17:49 ` Paul E. McKenney
2013-12-10 17:43 ` Peter Zijlstra
2013-12-10 18:49 ` Paul E. McKenney
2013-12-10 16:44 ` Oleg Nesterov
2013-12-10 17:15 ` Paul E. McKenney
2013-12-10 17:35 ` Oleg Nesterov
2013-12-10 1:28 ` [PATCH v5 tip/core/locking 6/7] locking: Add an smp_mb__after_unlock_lock() for UNLOCK+LOCK barrier Paul E. McKenney
2013-12-10 1:34 ` Josh Triplett
2013-12-10 5:26 ` Paul E. McKenney
2013-12-10 18:53 ` Paul E. McKenney
2013-12-10 12:37 ` Peter Zijlstra
2013-12-10 17:17 ` Paul E. McKenney [this message]
2013-12-10 17:45 ` Josh Triplett
2013-12-10 20:11 ` Paul E. McKenney
2013-12-10 17:04 ` Oleg Nesterov
2013-12-10 17:18 ` Paul E. McKenney
2013-12-10 17:32 ` Oleg Nesterov
2013-12-10 1:28 ` [PATCH v5 tip/core/locking 7/7] rcu: Apply smp_mb__after_unlock_lock() to preserve grace periods Paul E. McKenney
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