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Re: To see me always changes
Posted:
Feb 17, 2013 10:44 AM
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On Feb 17, 10:16 am, Shmuel (Seymour J.) Metz
<spamt...@library.lspace.org.invalid> wrote:
> In <DmJ5SKFdRQph-pn2-Iu4uIsOT7...@209-142-179-216.dyn.centurytel.net>,
> on 02/14/2013
> at 01:46 PM, wil...@nospam.pobox.com (Will Janoschka) said:
>
> >Then your thread safe code cannot call itself from within itself
>
> What gives you that idea? A procedure that is recursive and reentrant
> will generaly have local data on the stack, but that has nothing to do
> with making copies of other data.
Very interesting, and entirely not clear to me personally. I read and
I read, but I only remain confused regards this reentrancy. Recursion,
not a problem for me.
> >a local copy must be made for anything that changes changing
> >global data until final return from current instantiation would
> >cause computation that is circular.
>
> There is no such requirement, and no circularity. There is a
> requirement that changes to global data be serialized, but that
> applies whether it is done in the middle or just prior to return.
I was advised that global variables, because statics ought be safe,
are trouble for reentrant code. Can you please provide a short sample
list of which types of codes are reentrant. I understand printf is
one. I guess this issue is primarily relevant to event driven logic?
> >For example any part of an general interrupt routine that can be
> >interrupted must be reentrant. global variables can be used if
> >not changed in this instantiation.
>
> Interrupt routines often change global data, e.g., dispatch queues.
> BTW, they normally need to be reentrant even if they are
> noninterruptible, because there may be more than one processor.
I really need a good reference for interrupts and race conditions
logic. Any suggestions? Like Doctor McCoy would shout "I'm a reverse
engineer, not a computer scientist, DAMN IT?! Just feed me the answer
already... Tia."
> --
> Shmuel (Seymour J.) Metz, SysProg and JOAT <http://patriot.net/~shmuel>
>
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