Subject: Re: ingres and atomicity
To: None <>
From: der Mouse <mouse@Rodents.Montreal.QC.CA>
List: tech-userlevel
Date: 06/14/2005 23:24:48
>>> I know, but I'm a userland program, so I need a kernel service.
>> may need an architecture-dependent service, but that
>> doesn't necessarily mean a kernel service.  A routine [from] an OS
>> library such as libc might do as well.
> I see.  I've been assuming that atomic memory operations are
> privileged instructions available only to the kernel.  You and Jason
> are telling me that assumption doesn't hold across CPU architectures.

Right.  Sometimes it does, but sometimes not (eg, the VAX has some
half-dozen instructions which are totally nonprivileged but are
specifically defined to interlock properly against other CPUs in a MP
system, and which cannot be interrupted partly done even on when UP,
and which are thus useful in cases like this).

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