Path: utzoo!utgpu!water!watmath!clyde!rutgers!ucla-cs!zen!ucbvax!TAMSIGMA.BITNET!RSD1901
From: RSD1901@TAMSIGMA.BITNET (Shane Davis)
Newsgroups: comp.os.vms
Subject: AST interrupts and process state
Message-ID: <8801121623.AA23046@ucbvax.Berkeley.EDU>
Date: 11 Jan 88 21:43:00 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The ARPA Internet
Lines: 40

Hello again,

In lieu of a VMS Internals book (the one I had been using was borrowed and
the one from whom I borrowed it has taken a position elsewhere), I must
ask this question of the Info-VAX list.

Can a process in Local Event Flag Wait (LEF) state be interrupted by AST's
generated by $QIO requests? I do not want to complicate my program by nesting
hibernations and am not entirely sure if $WAKEing one hibernation will leave
the other pending hibernate intact or if it will wake the process altogether.
What I need to do is issue a $QIO to a mailbox and have its AST routine (as
given by the astadr parameter to the $QIO) interrupt the process for a short
time to let the sender of the mailbox message know that a resource is
unavailable while waiting for another QIO read request to a network (EXOS
TCP/IP is the software) to complete, signalling that a remote server has been
restarted. After the notification of the server restart has been received, the
program will then go back into HIB and wait for subsequent requests since the
resource is again available.

The routine in which all this is happening will also be entered from an AST
processing routine that was started while the process was under one $HIBER.
Thus, when the server is again reachable, the process should reenter HIB.
If I do use $HIBER to wait for the network QIO to complete, will a $WAKE
also elimintae the original $HIBER or only the one entered to wait for the
network?

The approach I'm using now is to use $SYNCH to wait for the network QIO to
complete, but writes to the forementioned mailbox must be processed even while
waiting for the network resource. So, after all this confusing explanation, I'll
restate my main question: can a process waiting for a single event flag be
interrupted by AST's? If not, will nested hibernations and wake-ups work?

After all this, I will probably just put a flag logical name in LNM$SYSTEM and
have it indicate to the mailbox message senders whether the resource is or is
not available.

Thanks in advance, and I hope you can think straight after my attempt at an
explanation of my dilemma. Please send responses to XPMAINT@TAMVENUS.BITNET.

--Shane Davis