Subject: Re: ingres and atomicity
To: None <tech-userlevel@NetBSD.org>
From: der Mouse <mouse@Rodents.Montreal.QC.CA>
Date: 06/14/2005 23:24:48
>>> I know, but I'm a userland program, so I need a kernel service.
>> No...you 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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