From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Jan Beulich <JBeulich@suse.com>,
xen-devel <xen-devel@lists.xenproject.org>
Subject: Re: [PATCH v2 6/6] x86/time: relax barriers
Date: Wed, 3 Aug 2016 14:11:23 +0100 [thread overview]
Message-ID: <3f4588c1-587d-aa6d-253c-1944c1c7b061@citrix.com> (raw)
In-Reply-To: <57A2080202000078001023AA@prv-mh.provo.novell.com>
On 03/08/16 14:04, Jan Beulich wrote:
> On x86 there's no need for full barriers in loops waiting for some
> memory location to change. Nor do we need full barriers between two
> reads and two writes - SMP ones fully suffice (and I actually think
> they could in fact be dropped, since atomic_*() operations should
> already provide enough ordering).
Missing a SoB,
Which "ones" are you referring to? atomic_*() is only ordered with
respect to the atomic_t used.
Overall, I think the change is correct, so Reviewed-by: Andrew Cooper
<andrew.cooper3@citrix.com>
There are definitely more mis-uses of mandatory barriers in Xen,
although I haven't done a full audit yet.
~Andrew
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next prev parent reply other threads:[~2016-08-03 13:11 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-03 12:55 [PATCH v2 0/6] x86/time: improve cross-CPU clock monotonicity (and more) Jan Beulich
2016-08-03 13:00 ` [PATCH v2 1/6] x86/time: calibrate TSC against platform timer Jan Beulich
2016-08-03 13:07 ` Andrew Cooper
2016-08-03 13:00 ` [PATCH v2 2/6] x86/time: correctly honor late clearing of TSC related feature flags Jan Beulich
2016-08-17 13:41 ` Ping: " Jan Beulich
2016-08-03 13:01 ` [PATCH v2 3/6] x86/time: support 32-bit wide ACPI PM timer Jan Beulich
2016-08-03 13:02 ` [PATCH v2 4/6] x86/time: fold recurring code Jan Beulich
2016-08-03 13:03 ` [PATCH v2 5/6] x86/time: group time stamps into a structure Jan Beulich
2016-08-03 13:04 ` [PATCH v2 6/6] x86/time: relax barriers Jan Beulich
2016-08-03 13:11 ` Andrew Cooper [this message]
2016-08-03 13:22 ` Jan Beulich
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