Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cornell!batcomputer!itsgw!steinmetz!davidsen
From: davidsen@steinmetz.ge.com (William E. Davidsen Jr)
Newsgroups: comp.unix.xenix
Subject: Re: system lockup
Keywords: bug?
Message-ID: <13161@steinmetz.ge.com>
Date: 16 Feb 89 18:43:59 GMT
References: <60@estinc.UUCP>
Reply-To: davidsen@crdos1.UUCP (bill davidsen)
Organization: General Electric CRD, Schenectady, NY
Lines: 34

In article <60@estinc.UUCP> fnf@estinc.UUCP (Fred Fish) writes:

| 	static char buf [1024 * 1024];
| 
| 	main ()
| 	{
| 		write (0, buf, sizeof (buf));
| 	}
| 
| Can anyone else confirm similar symptoms?

  You're right! All of my programs which write huge arrary to the
keyboard don't work under Xenix! Seriously, I think there are two
problems here, one of which is you're trying to write to an input file.
If that hangs your system it's a bug. 

Begin unsupported hypothesis
____________________________

  When you are writing a huge, uninitialized, array, I *believe* that it
is not paged from the disk but created and zeroed on the fly on demand.
This could get the CPU very busy in kernel and hang the system until
done. If you don't have a lot of memory you will probably start paging
some of the newly created pages out. There may well be a problem in
doing a write which gets a page fault while setting up the i/o.

  I borrowed a system at work to try this, and it did not hang anything.
I was able to change to other virtual screens, etc. I'm not sure what
writing to the keyboard does, but it didn't hurt anything. Xenix/386
v2.3.1 on a Dell325.
-- 
	bill davidsen		(wedu@ge-crd.arpa)
  {uunet | philabs}!steinmetz!crdos1!davidsen
"Stupidity, like virtue, is its own reward" -me