Date: Wed, 16 Feb 2011 15:39:53 -0500
From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: David Daney <ddaney@caviumnetworks.com>
Cc: Roland McGrath <roland@redhat.com>, Mark Wielaard <mjw@redhat.com>,
        Stefan Hajnoczi <stefanha@gmail.com>,
        "Frank Ch. Eigler" <fche@redhat.com>,
        Julien Desfossez <julien.desfossez@polymtl.ca>,
        dominique.toupin@ericsson.com, ltt-dev@lists.casi.polymtl.ca,
        systemtap@sources.redhat.com, linux-kernel@vger.kernel.org,
        Jason Baron <jbaron@redhat.com>, hpa@zytor.com, rostedt@goodmis.org,
        mingo@elte.hu, tglx@linutronix.de, andi@firstfloor.org, rth@redhat.com,
        masami.hiramatsu.pt@hitachi.com, fweisbec@gmail.com, avi@redhat.com,
        davem@davemloft.net, sam@ravnborg.org, michael@ellerman.id.au,
        Peter Zijlstra <peterz@infradead.org>
Subject: Re: Porting "jump labels" to userspace
Message-ID: <20110216203953.GB2015@Krystal>
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* David Daney (ddaney@caviumnetworks.com) wrote:
> On 02/16/2011 12:04 PM, Roland McGrath wrote:
>> IMHO there is not really so much to the in-kernel implementation that it's
>> worth attempting to reuse the code in userland.  Pretty much all the work
>> is in the details of the implementation that would naturally differ a lot
>> in a different context.  If you understand the mechanism and the machine
>> details, then implementing it well for a userland context is not a big deal
>> and is cleaner to do from scratch than shoe-horning kernel-centric code
>> into a wildly different context.
>>
>
> Good point.
>
> Certainly the details of maintaining instruction cache coherency may be  
> different in userspace.

Indeed, the arch-specific parts will need some extra care (which might, in the
worse case scenario, require to suspend a whole process during the update), but
the generic code in jump_label.c and jump_label.h could certainly be reused.

Thanks,

Mathieu

>
> David Daney

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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