From owner-freebsd-hackers  Wed Jan 31 23:48:23 2001
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Date: Wed, 31 Jan 2001 23:47:31 -0800
From: Julian Elischer <julian@elischer.org>
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To: John Baldwin <jhb@FreeBSD.org>
Cc: Matthew Emmerton <matt@gsicomp.on.ca>,
	freebsd-hackers@FreeBSD.org
Subject: Re: Atomic bit operations
References: <XFMail.010131151628.jhb@FreeBSD.org>
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John Baldwin wrote:
> 
> On 31-Jan-01 Matthew Emmerton wrote:
> > Hi all,
> >
> > I've taken a look around for an implementation of atomic bit operations in
> > FreeBSD (similar to Linux' asm/bitopt.h, which include clear_bit() and
> > test_and_set_bit()) but haven't found any.  The only thing I've found are
> > the atomic clear/set/add/sub routines in machine/atomic.h.
> >
> > Do we have an implementation of atomic bit operations, and if we don't,
> > would we like some?
> 
> Erm, atomic_set() sets's bits, and atomic_clear() clear's bits.  Anything else
> you might need can be done with atomic_cmpset() anyways.  Also, atomic
> operations are very hard to debug, esp. to check for race conditions, so there
> direct use is discouraged.  Instead, use a higher level primitive such as a
> mutex or other appropriate lock.  There is also talk of a potential abstract
> refcount type so that simple reference counts can be optimized, though that has
> been shot down thus far.

by who?? I really want this....

> 
> > --
> > Matt Emmerton
> 
> --
> 
> John Baldwin <jhb@FreeBSD.org> -- http://www.FreeBSD.org/~jhb/
> PGP Key: http://www.baldwin.cx/~john/pgpkey.asc
> "Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/
> 
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-- 
      __--_|\  Julian Elischer
     /       \ julian@elischer.org
    (   OZ    ) World tour 2000-2001
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            v


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