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Date:      Fri, 10 Feb 1995 12:04:12 -0600
From:      Mark Tinguely <tinguely@plains.nodak.edu>
To:        peter@bonkers.taronga.com, terry@cs.weber.edu
Cc:        davidg@Root.COM, hackers@FreeBSD.org, jmb@kryten.atinc.com
Subject:   Re: MIT SHM X11 extensions? (fwd)
Message-ID:  <199502101804.AA23116@plains.NoDak.edu>

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Terry says:

> Uh, why is ETXTBUSY still around?

because no one has taken the time to fix it right. I agree it should go.

  > What else would you do if you opened a currently running executable for
  > writing?

Terry also says:

>  Actually, you could fault the whole image to swap and close the
>  reference to the file -- and just allow the write, with never an
>  ETXTBUSY to be seen.

or keep the file in the filesystem and the vnode pager can refer to the correct
vnode of text. the debate could be should we keep the swap backstore
requirements small (local drives are small NFS servers are big or the local
machines drives are getting bigger and can handle it).  my bias is small swap
backstore, big filesystems containing text.

(of course the filesystem switch-a-roo response to the problem has difficulties
when (time sequence):
 open execute
 open write (save old file -- any new executes will use this)
 close write
 open execute (should use new executable)
 open write (backup vnode pointer being used what now? make the backup
 	     vnode pointer an array?)
 ...

we talked about this before on the net. the one consideration is should
all executables be in swap, so that we can restart the apps where we stopped
(notebook memory saver philosophy). or very least all NFS on swap because
they are too dump to figure about writes.

it would be stupid to re-work ETXTBUSY and then change it again. the underlining
questions have not been solved, so nothing has been done.

--mark.



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