There have been extensive discussions on this over the last two
years or so [that I've been aware of] on this list about whether such an
animal can even exist in the strict sense of "real-time". While it probably
can't in general(i.e. it can't be totally deterministic), under some
circumstances it's feasible. These would include those instances when the
total memory requirements are predictable and limited but then I fail to see
the difference between what you propose under those circumstances and a
simple parcel-out-preallocated-memory routine.
The real problem with a rt_malloc() -- as I see it -- is the
question of where would it get its memory from. The only possible solution
would be to write something that sits on top of ordinary kmalloc(). But the
fundamental problems -- which Victor can, and has, explain better than I --
is that if there's no in-core memory available, you'd have to swap something
to disk to free up memory so then you'd have to write a rt_disk_driver and
... Pretty soon you've completely rewritten the whole kernel and you have
no one to do the alpha testing except yourself and who do you turn to if
there's a problem. In summary, I don't see this as a practical alternative.
Norm
-----Original Message-----
From: Ken Emmons, Jr. [mailto:[EMAIL PROTECTED]]
Sent: Friday, December 07, 2001 10:04 AM
To: [EMAIL PROTECTED]
Subject: Re: RE: [rtl] malloc, timers, and crashes.
Hello,
It has been pointed out that kernel calls(including kmalloc) cannot be
called from within RT. That is kind of what I expected after finding this
bug, but I was hopping that there would be some solution for having an
equivelent of a malloc() call. I was thinking of writing a rt_malloc()
function.
What do you folks think about this? Has anyone else written it yet??
~Ken
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