linux-kernel - Re: [PATCH v4 1/3] make jump_labels wait while updates are in place

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Message-ID: <1335535630.28106.209.camel@gandalf.stny.rr.com>
Date:	Fri, 27 Apr 2012 10:07:10 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Jason Baron <jbaron@...hat.com>
Cc:	Glauber Costa <glommer@...allels.com>, cgroups@...r.kernel.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	Li Zefan <lizefan@...wei.com>, Tejun Heo <tj@...nel.org>,
	kamezawa.hiroyu@...fujitsu.com, linux-mm@...ck.org,
	devel@...nvz.org, Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.cz>, Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH v4 1/3] make jump_labels wait while updates are in place

On Fri, 2012-04-27 at 09:53 -0400, Jason Baron wrote:

> Right, for x86 which uses stop_machine currently, we guarantee that all
> cpus are going to see the updated code, before the inc of key->enabled.
> However, other arches (sparc, mips, powerpc, for example), seem to be
> using much lighter weight updates, which I hope are ok :)

And x86 will soon be removing stop_machine() from its path too. But all
archs should perform some kind of memory sync after patching code. Thus
the update should be treated as if a memory barrier was added after it,
and before the inc.

-- Steve


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