From: pbonzini@redhat.com (Paolo Bonzini)
Subject: [ltt-dev] [URCU PATCH] cmm: provide lightweight rmb/wmb on PPC
Date: Wed, 21 Sep 2011 09:20:08 +0200 [thread overview]
Message-ID: <4E799028.1010707@redhat.com> (raw)
In-Reply-To: <20110920165115.GA2955@Krystal>
On 09/20/2011 06:51 PM, Mathieu Desnoyers wrote:
>> > I think you're right. "eieio;lwsync" is good for rmb, lwsync is good for
>> > wmb/smp_rmb/smp_wmb.
> I'm not convinced that the "eieio; lwsync" combo would provide the
> ordering we're looking for for cmm_rmb(). AFAIK, eieio orders,
> separately, a) cacheable stores and b) loads and stores to non-cacheable
> memory. AFAIK, lwsync orders cacheable memory ops, but not loads with
> respect to previous stores. So basically, this combo lacks ordering of
> non-cacheable memory accesses with respect to cachable memory accesses.
Yeah, better safe than sorry.
> Why would lwsync be good for cmm_wmb ? Does it order non-cacheable
> writes ?
The manuals say non-cacheable writes are always ordered.
Paolo
next prev parent reply other threads:[~2011-09-21 7:20 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-20 7:12 Paolo Bonzini
2011-09-20 16:31 ` Mathieu Desnoyers
2011-09-20 16:39 ` Paolo Bonzini
2011-09-20 16:51 ` Mathieu Desnoyers
2011-09-21 7:20 ` Paolo Bonzini [this message]
2011-09-21 23:43 ` Paul E. McKenney
2011-09-21 23:42 ` Paul E. McKenney
2011-09-22 8:42 ` [ltt-dev] [PATCH v2] cmm: provide lightweight smp_rmb/smp_wmb " Paolo Bonzini
2011-09-22 9:10 ` Mathieu Desnoyers
2011-09-22 14:49 ` Paul E. McKenney
2011-09-22 14:57 ` Mathieu Desnoyers
2011-09-22 15:26 ` Paul E. McKenney
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