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From: LaMont Jones <lamont@security.hp.com>
To: Matthew Wilcox <Matthew.Wilcox@genedata.com>
Cc: parisc-linux@thepuffingroup.com, lamont@security.hp.com
Subject: Re: [parisc-linux] xchg implementation
Date: Mon, 01 Nov 1999 14:03:05 -0700	[thread overview]
Message-ID: <19991101210305.75FA118708@security.hp.com> (raw)
In-Reply-To: Your message of "Sun, 31 Oct 1999 19:37:39 +0100." <19991031193739.V516@mencheca.ch.genedata.com>

> This is a uniprocessor optimisation of the xchg() case where it's _not_
> exchanging with zero.  What I need is a spare CR register.  As far as I
> can see from the comments, CR28-30 are currently reserved; leaving CRs
> 24, 25 and 31 available.  Unless someone's using one of them without
> documenting it somewhere...?  That really does need to be written down
> somewhere.

IIRC, CR24 and 25 are readable from user space (not writable), and can be
quite useful for thread specific data, thread id, etc...  It might do to
leave them available for such a use.

lamont

  reply	other threads:[~1999-11-01 21:02 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
1999-10-31 18:37 [parisc-linux] xchg implementation Matthew Wilcox
1999-11-01 21:03 ` LaMont Jones [this message]
1999-11-02  8:53   ` Matthew Wilcox
1999-11-02 14:10     ` LaMont Jones
1999-11-06 19:22     ` Philipp Rumpf

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