linux-mips
[Top] [All Lists]

Re: [libc-alpha] Re: PATCH: Fix ll/sc for mips

To: kaz@ashi.footprints.net
Subject: Re: [libc-alpha] Re: PATCH: Fix ll/sc for mips
From: Hiroyuki Machida <machida@sm.sony.co.jp>
Date: Fri, 01 Feb 2002 13:59:03 +0900 (JST)
Cc: hjl@lucon.org, macro@ds2.pg.gda.pl, libc-alpha@sources.redhat.com, linux-mips@oss.sgi.com
In-reply-to: <Pine.LNX.4.33.0201311952440.2305-100000@ashi.FootPrints.net>
References: <20020201.123523.50041631.machida@sm.sony.co.jp> <Pine.LNX.4.33.0201311952440.2305-100000@ashi.FootPrints.net>
Sender: owner-linux-mips@oss.sgi.com
From: Kaz Kylheku <kaz@ashi.footprints.net>
Subject: Re: [libc-alpha] Re: PATCH: Fix ll/sc for mips
Date: Thu, 31 Jan 2002 20:02:25 -0800 (PST)

> On Fri, 1 Feb 2002, Hiroyuki Machida wrote:
> > Please note that "sc" may fail even if nobody write the
> > variable. (See P.211 "8.4.2 Load-Linked/Sotre-Conditional" of "See 
> > MIPS RUN" for more detail.) 
> > So, after your patch applied, compare_and_swap() may fail, even if
> > *p is equal to oldval.
> 
> I can't think of anything that will break because of this, as long
> as the compare_and_swap eventually succeeds on some subsequent trial.
> If the atomic operation has to abort for some reason other than *p being
> unequal to oldval, that should be cool.

I mean that this patch breaks the spec of compare_and_swap().

In most case, this patch may works as Kaz said. If this patch have
no side-effect to any application, it's ok to apply the patch. But
we can't know how to use compare_and_swap() in all aplications in a
whole world. So we have to follow the spec.  


---
Hiroyuki Machida
Sony Corp.

<Prev in Thread] Current Thread [Next in Thread>