Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!utgpu!water!watnot!watmath!clyde!rutgers!ames!ucbcad!ucbvax!YALE.ARPA!LEICHTER-JERRY From: LEICHTER-JERRY@YALE.ARPA.UUCP Newsgroups: mod.computers.vax Subject: Re: Processes in a RWAST state Message-ID: <8703170506.AA04532@ucbvax.Berkeley.EDU> Date: Tue, 17-Mar-87 00:06:44 EST Article-I.D.: ucbvax.8703170506.AA04532 Posted: Tue Mar 17 00:06:44 1987 Date-Received: Wed, 18-Mar-87 03:20:43 EST Sender: daemon@ucbvax.BERKELEY.EDU Reply-To: Distribution: world Organization: The ARPA Internet Lines: 37 Approved: info-vax@sri-kl.arpa [W]hen I'm debugging some new hardware and software, sometimes a process will get into an RWAST state and DCL cannot kill it. I spoke to the DEC folks in Colorado and they confirmed that reboot is the only option here (I had been using STOP/ID=nnn, which gives no error message, but doesn't do anything either). Can anyone give me a more favorable second opinion? Is rebooting the only option to getting rid of a process in the RWAST state? If so, why does DEC allow VMS to create processes that it can't delete? RWAST is a kind of a catch-all wait state: It means the process needs some resource that it currently can't get, but it is expected that the delivery of an AST will make some of that resource available. A common example occurs when a process issues a QIO for buffered I/O but already has as many outstand- ing buffered I/O requests as it is allowed (BIOlm). A completely different example occurs when a process that has ACP/XQP work outstanding is deleted; it will wait in RWAST state until that work completes. Not all RWAST processes are undeletable. The example you cite involving the TK50 is probably undeletable because it is waiting for the mag tape ACP to finish the operation it requested, which will never happen. VMS can't delete the process because it would leave the ACP confused. (The ACP might possibly be taught to deal with that, but in the case of XQP operations, which are really taking place within the process, deleting the process while the XQP is busy stands a good chance of corrupting a disk.) There will always be cases in any operating system in which a process hangs while in a some state - such as holding some important resource like a low- level disk structure, which it may or may not have modified into some inter- mediate state - in which it cannot be safely deleted. Such a "dead" process often isn't really doing anything harmful - it's just that the OS can't be SURE, so has to assume the worst. It costs you very little to just leave the RWAST (or whatever) process alone; in most cases, you don't HAVE to re- boot. -- Jerry -------