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Date: Mon, 6 Oct 2014 10:38:29 +0400 From: Vladimir Davydov <vdavydov@...allels.com> To: Michal Hocko <mhocko@...e.cz> CC: Johannes Weiner <hannes@...xchg.org>, <linux-mm@...ck.org>, Greg Thelen <gthelen@...gle.com>, Dave Hansen <dave@...1.net>, <cgroups@...r.kernel.org>, <linux-kernel@...r.kernel.org> Subject: Re: [patch 1/3] mm: memcontrol: lockless page counters On Fri, Oct 03, 2014 at 05:41:34PM +0200, Michal Hocko wrote: > 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. Thank you for the info, now it's clear to me. Thanks, Vladimir -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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