From: pbonzini@redhat.com (Paolo Bonzini)
Subject: [ltt-dev] [URCU PATCH] caa: do not generate code for rmb/wmb on x86_64, rmb on i686
Date: Mon, 05 Sep 2011 17:15:19 +0200 [thread overview]
Message-ID: <4E64E787.2040208@redhat.com> (raw)
In-Reply-To: <BLU0-SMTP648D3439671501BF3EC1AE961D0@phx.gbl>
On 09/05/2011 05:12 PM, Mathieu Desnoyers wrote:
>> In userspace we can assume no accesses to write-combining memory occur,
>> > and also that there are no non-temporal load/stores (people would presumably
>> > write those with assembly or intrinsics and put appropriate lfence/sfence
>> > manually). So rmb and wmb are no-ops on x86.
>
> What about memory barriers for DMA with devices ? For these, we might
> want to define cmm_wmb/rmb and cmm_smp_wmb/rmb differently (keep the
> fences for DMA accesses).
Yes, splitting wmb/rmb and smp_wmb/rmb makes sense.
Paolo
next prev parent reply other threads:[~2011-09-05 15:15 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-05 11:27 Paolo Bonzini
2011-09-05 15:12 ` Mathieu Desnoyers
[not found] ` <BLU0-SMTP648D3439671501BF3EC1AE961D0@phx.gbl>
2011-09-05 15:15 ` Paolo Bonzini [this message]
2011-09-05 15:32 ` Mathieu Desnoyers
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