Subject:
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Re: signals / legOS internals
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Newsgroups:
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lugnet.robotics.rcx.legos
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Date:
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Wed, 23 Jun 1999 21:15:32 GMT
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Viewed:
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1065 times
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Ola Liljedahl wrote:
> Why signals?!?
Because they are useful at times, and Markus directed me to implement them. I
think the upcoming network code is going to use them, too (at least, that's
what I heard). Just 'cause they're there doesn't mean you have to use them.
> Unix-style asynchronous signals is the last feature I would
> ever want to implement or use. Brain-dead and very dangerous
> "feature".
How do you figure?
> As you write; "The problem is that a signal can
> happen at any time".
Yes, they can. What is the problem, from the user's prospective, with that?
My issue dealt specifically with not polluting the stack when servicing a
software interrupt within the task scheduler in the kernel. It turned out to
be a non-problem, but it did jog my memory with regard to the need to goose
the SP in my hand-written signal handler wrapper.
> You shouldn't pass this problem on to the
> application writer, it should be handled in the kernel
That is where I am implementing it. The application writer need only deal
with the API, assuming they choose to use signals at all. The API will be
familiar to anyone who has used POSIX signals.
> and
> reliable (synchronous) mechanisms (for instance semaphores,
> message queues or OSE style message passing) should be presented
> to the application.
We have semaphores.
Please enlighten me WRT OSE style message passing. The TLA is unfamiliar to
me.
I brought up message/event queues awhile back, and there was some argument
against them. I lost.
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Message has 1 Reply:
 | | RE: signals / legOS internals
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| (...) Ummmmm, I don't want to speak for Markus, but most embedded kernels (and I use a lot of them) use the term signal and semaphore interchangably. I'm willing to bet a couple of bricks that the intent is to implement semaphores to facilitate (...) (25 years ago, 23-Jun-99, to lugnet.robotics.rcx.legos)
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Message is in Reply To:
| | Re: signals / legOS internals
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| (...) Why signals?!? Unix-style asynchronous signals is the last feature I would ever want to implement or use. Brain-dead and very dangerous "feature". As you write; "The problem is that a signal can happen at any time". You shouldn't pass this (...) (25 years ago, 23-Jun-99, to lugnet.robotics.rcx.legos)
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