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Re: [avr-libc-dev] Should cli() imply a memory barrier?

From: Paulo Marques
Subject: Re: [avr-libc-dev] Should cli() imply a memory barrier?
Date: Tue, 08 Jun 2010 20:23:23 +0100
User-agent: Thunderbird (X11/20090817)

Bob Paddock wrote:
>> This raises the question: Some years ago, a discussion about whether
>> cli() should include a memory barrier ended with an agreement that
>> it's not needed.
> cli() should produce code of "least surprise".  Most people are
> surprised when they find their explicitly placed cli() has been
> (re)moved by code reordering.
> atomic.h should be mentioned if the documentation route is the one
> chosen.  Seems like there is some overlap here?

I agree with the "least surprise" argument, and that we should mention
atomic.h in the documentation.

One thing we could do for the programmers that want to use the "raw" cli
version and know what they are doing is to keep a "__cli" or "__raw_cli"
version (or some other name) that just emits a single "cli" instruction.

Paulo Marques
Software Development Department - Grupo PIE, S.A.
Phone: +351 252 290600, Fax: +351 252 290601
Web: www.grupopie.com

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