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Re: PATCH: Always use ll/sc for mips

To: "Maciej W. Rozycki" <macro@ds2.pg.gda.pl>
Subject: Re: PATCH: Always use ll/sc for mips
From: "H. J. Lu" <hjl@lucon.org>
Date: Wed, 17 Jul 2002 08:01:57 -0700
Cc: Ulrich Drepper <drepper@redhat.com>, linux-mips@oss.sgi.com, GNU C Library <libc-alpha@sources.redhat.com>
In-reply-to: <Pine.GSO.3.96.1020717095946.13355C-100000@delta.ds2.pg.gda.pl>; from macro@ds2.pg.gda.pl on Wed, Jul 17, 2002 at 10:31:13AM +0200
References: <20020716084208.A21699@lucon.org> <Pine.GSO.3.96.1020717095946.13355C-100000@delta.ds2.pg.gda.pl>
Sender: owner-linux-mips@oss.sgi.com
User-agent: Mutt/1.2.5.1i
On Wed, Jul 17, 2002 at 10:31:13AM +0200, Maciej W. Rozycki wrote:
> On Tue, 16 Jul 2002, H. J. Lu wrote:
> 
> > >  It sucks performance-wise with no visible gain, so I don't think it is
> > > really desireable.  Since the no-ll/sc case is handled correctly, I see no
> > 
> > Only <sys/tas.h> is covered by the kernel interface. But it doesn't
> > cover atomicity.h in glibc and libstdc++.
> 
>  Even if nobody bothered fixing these, that doesn't mean some other code
> is useless.  If you don't want to implement these with _test_and_set(),
> then just put equivalent ll/sc code there, which will work thanks to the
> emulation.  Depending on the operation it may even be faster than
> _test_and_set() as ll/sc provides a generic way to perform atomic
> operations, while using _test_and_set() might require a spinlock. 
> 

I am not against reversing the sysdeps/unix/sysv/linux/mips/sys/tas.h
change. But I am not so excited about it to do it myself.


H.J.


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