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From: karlton@sgi.com (Phil Karlton)
Newsgroups: comp.windows.x
Subject: Re: Problem with Signals
Message-ID: <4826@odin.SGI.COM>
Date: 2 Mar 90 21:09:29 GMT
References: <132399@sun.Eng.Sun.COM> <9002281729.AA02895@wilkins.bcm.tmc.edu>
Sender: news@odin.SGI.COM
Reply-To: karlton@sgi.com
Organization: Silicon Graphics, WorkGroup Products Division
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This is what happened to VMS as the result of X (if memory serves me
right). The LockDisplay and UnlockDisplay macro invocations that
surround every Xlib routine were defined to set or clear a particular
bit in the client's address space. (This is a relatively cheap
operation.) Then the OS was changed so that if the bit was set the AST
was not delivered to the process until the bit was cleared. This
prevents the "interrupt" routines from running while a partial X request
was in an I/O buffer. I am not going to hold my breath until all of the
various UNIX vendors add a similar feature.

One might consider merely using a different X connection for
communicating with the server while in any interrupt routine. Adequate
support within the intrinsics for dealing with mulitple connections and
reentrancy would be necessary to make this viable for Xt based clients.

PK