From: CRDGW2::CRDGW2::MRGATE::"SMTP::CRVAX.SRI.COM::RELAY-INFO-VAX" 29-AUG-1989 08:47 To: MRGATE::"ARISIA::EVERHART" Subj: SNAP & WATCH, user beware! Message-Id: <8908291241.AA21340@crdgw1.ge.com> Received: From KL.SRI.COM by CRVAX.SRI.COM with TCP; Tue, 29 AUG 89 05:18:46 PDT Received: from drcvax.af.mil by KL.SRI.COM with TCP; Tue, 29 Aug 89 05:08:41 PDT Date: 29 Aug 89 07:54:00 EST From: "Daniel J. Graham" Subject: SNAP & WATCH, user beware! To: "info-vax" Hi all, Before I send off part 3 of SNAP, I want to clearly state a difficulty that some kind soul pointed out to me. As you know, the old MACRO device SETIPL for privileged code has been replaced with what are called "spinlocks." There are two places in this program where MACRO routines used to use SETIPL calls: LIB_DEFAULT_DIR, the macro routine that SNAP uses to find out the default directory of the observed process, it must execute an AST within the context of the user's process to translate SYS$DISK. The second instance is in the program WATCH, which observes another's terminal input/output. Both of these routines have had some spinlocks implemented, but they still have SETIPL calls too. I am no MACRO whix, and can't debug them further than they have already been. Other programmers, far better than I have attempted to do so, with no success. We just can't seem to get them to operate without those generated warnings. This is both a caution and a plea: Many have used SMAP/WATCH on MP systems, with no crashes. This does NOT mean that it cannot cause one. If two competing processes attempt to grap a structure, the system will most likely crash. Because it hasen't happened, doesn't mean it won't. I repeat, however, that I k,now of no crashes of MP systems yet... Now the plea: Is there anyone willing to take the two modules, LIB_DEFAULT_DIR.MAR and WATCH.MAR and try to exorcise the SETIPLs? If so, just wait a day or so and all parts of SNAP with the routines will have been posted. I wrote neither of the MACRO routines, and have no pride relative to their being modified. I'll accept anyone's assistance. Have fun all, part 3 of 8 follows in a little while. Dan Graham