From: Michal Hocko <mhocko@suse.cz>
To: Vladimir Davydov <vdavydov@parallels.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>,
linux-mm@kvack.org, Greg Thelen <gthelen@google.com>,
Dave Hansen <dave@sr71.net>,
cgroups@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [patch 1/3] mm: memcontrol: lockless page counters
Date: Fri, 3 Oct 2014 17:41:34 +0200 [thread overview]
Message-ID: <20141003154134.GG4816@dhcp22.suse.cz> (raw)
In-Reply-To: <20141003153623.GA1162@esperanza>
On Fri 03-10-14 19:36:23, Vladimir Davydov wrote:
> On Thu, Oct 02, 2014 at 08:07:48AM -0400, Johannes Weiner wrote:
[...]
> > The barriers are implied in change-return atomics, which is why there
> > is an xchg. But it's clear that this needs to be documented. This?:
>
> With the comments it looks correct to me, but I wonder if we can always
> rely on implicit memory barriers issued by atomic ops. Are there any
> archs where it doesn't hold?
xchg is explcitly mentioned in Documentation/memory-barriers.txt so it
is expected to be barrier on all archs. Besides that not all atomic ops
imply memory barriers. Only those that "modifies some state in memory
and returns information about the state" do.
--
Michal Hocko
SUSE Labs
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next prev parent reply other threads:[~2014-10-03 15:41 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-24 15:43 [patch 0/3] mm: memcontrol: lockless page counters v2 Johannes Weiner
2014-09-24 15:43 ` [patch 1/3] mm: memcontrol: lockless page counters Johannes Weiner
2014-09-26 10:31 ` Vladimir Davydov
2014-10-02 12:07 ` Johannes Weiner
2014-10-03 15:36 ` Vladimir Davydov
2014-10-03 15:41 ` Michal Hocko [this message]
2014-10-06 6:38 ` Vladimir Davydov
2014-09-30 11:06 ` Michal Hocko
2014-10-02 15:01 ` Johannes Weiner
2014-10-02 19:52 ` Johannes Weiner
2014-10-03 15:44 ` Michal Hocko
2014-10-03 14:50 ` Michal Hocko
2014-10-07 15:15 ` Michal Hocko
2014-10-08 12:31 ` Johannes Weiner
2014-09-24 15:43 ` [patch 2/3] mm: hugetlb_controller: convert to " Johannes Weiner
2014-09-26 11:25 ` Vladimir Davydov
2014-10-07 15:21 ` Michal Hocko
2014-10-08 12:39 ` Johannes Weiner
2014-09-24 15:43 ` [patch 3/3] kernel: res_counter: remove the unused API Johannes Weiner
2014-09-26 11:27 ` Vladimir Davydov
2014-10-07 15:26 ` Michal Hocko
2014-10-14 1:46 [patch 0/3] mm: memcontrol: lockless page counters v3 Johannes Weiner
2014-10-14 1:46 ` [patch 1/3] mm: memcontrol: lockless page counters Johannes Weiner
2014-10-14 15:56 ` Michal Hocko
2014-10-14 16:33 ` Johannes Weiner
2014-10-15 9:40 ` Michal Hocko
2014-10-17 7:47 ` Vladimir Davydov
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