From: himel@mips.UUCP (Mark I. Himelstein)
Subject: Re: Microsoft OS/2 -- Ideal for Ada
Date: Wed, 17-Jun-87 00:14:51 EDT [thread overview]
Date: Wed Jun 17 00:14:51 1987
Message-ID: <459@gumby.UUCP> (raw)
In-Reply-To: 1624@aw.sei.cmu.edu
In article <1624@aw.sei.cmu.edu> firth@bd.sei.cmu.edu.UUCP writes:
...
>I agree that it is inappropriate to map Ada tasks into Unix processes.
>For one thing, the overhead is insupportable.
I agree too mainly due the horrible overhead of unix processes and the
shared nature of the ada memory model.
>Unfortunately, the alternative doesn't work either. Two serious
>problems
I presume you mean multi-tasks within one unix process.
>(a) Unix does not provide asynchronous IO to a process. If one Ada task
> does a read() from the terminal, the whole program blocks. And you
> thought polling died out in the '60s?
BSD UNIX provides full asynchronous IO. This is done with ioctl's and fcntl's
and setting up a signal handler for SIGIO.
>(b) A large number of Unix system calls are not reentrant. If one Ada
> task is suspended in a malloc(), chaos can ensue.
Since Ada tasks would share memory, allocating from a shared heap like malloc
represents a critical region and other tasks should be blocked.
Mark I. Himelstein
decwrl!mips!himel
next prev parent reply other threads:[~1987-06-17 4:14 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
1987-06-13 0:06 Microsoft OS/2 -- Ideal for Ada Herm Fischer
1987-06-15 11:40 ` martillo
1987-06-16 12:50 ` Robert Firth
1987-06-16 22:24 ` martillo
1987-06-17 4:14 ` Mark I. Himelstein [this message]
1987-06-17 22:13 ` Yakim Martillo
-- strict thread matches above, loose matches on Subject: below --
1987-06-17 16:28 "VAXR::IVANOVIC"
1987-06-19 11:33 ` martillo
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