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Message-ID: <4E948E48.60205@cavium.com>
Date:   Tue, 11 Oct 2011 11:43:20 -0700
From:   David Daney <david.daney@cavium.com>
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To:     Joe Buehler <aspam@cox.net>
CC:     linux-mips@linux-mips.org
Subject: Re: using mprotect to write to .text
References: <loom.20111010T215444-70@post.gmane.org> <4E9470A1.8020309@cavium.com> <4E947D8A.9090409@cox.net> <4E948593.6030604@cavium.com> <4E948C62.3000802@cox.net>
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Two points you may not be aware of:

1) cacheflush() clears all hazards.

2) There are no hazards on Octeon.


On 10/11/2011 11:35 AM, Joe Buehler wrote:
> David Daney wrote:
>
>> I cannot parse the meaning out of these last two sentences.  The
>> cacheflush() system call both exists and works.  You want to change it?
>
> Let me rewind a bit.  I have a multithreaded binary running on multiple
> physical CPUs.  As part of a debugging mechanism, I want to make changes
> to .text from a thread dedicated to the purpose.  This requires at the
> least icache flushes on all CPUs but also hazard avoidance measures on
> all CPUs.  So I understand anyway.
>
> The cacheflush call will do the flush but not the hazard avoidance.  In
> order to solve my particular issue I am thinking about adding the hazard
> avoidance into cacheflush for my particular application.  It is not a
> question of cacheflush being wrong, but of extending it to meet my
> needs.  In fact, it seems like a useful change -- it will allow an
> application to do exactly what I want to do, and easily so, and would
> seem a logical place for the functionality to reside.
>
> Sorry if I seem a bit muddled -- this is extremely low level and not
> what I deal with day to day.
>
> Joe Buehler
>