Thread (305 messages) 305 messages, 27 authors, 2007-09-11

Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures

From: Herbert Xu <herbert@gondor.apana.org.au>
Date: 2007-08-16 02:10:17
Also in: linux-arch, lkml

On Thu, Aug 16, 2007 at 07:45:44AM +0530, Satyam Sharma wrote:
Completely agreed, again. To summarize again (had done so about ~100 mails
earlier in this thread too :-) ...

atomic_{read,set}_volatile() -- guarantees volatility also along with
atomicity (the two _are_ different concepts after all, irrespective of
whether callsites normally want one with the other or not)

atomic_{read,set}_nonvolatile() -- only guarantees atomicity, compiler
free to elid / coalesce / optimize such accesses, can keep the object
in question cached in a local register, leads to smaller text, etc.

As to which one should be the default atomic_read() is a question of
whether majority of callsites (more weightage to important / hot
codepaths, lesser to obscure callsites) want a particular behaviour.

Do we have a consensus here? (hoping against hope, probably :-)
I can certainly agree with this.

But I have to say that I still don't know of a single place
where one would actually use the volatile variant.

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} [off-list ref]
Home Page: http://gondor.apana.org.au/~herbert/
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