From: utzoo!decvax!harpo!eagle!mhtsa!alice!rabbit!pjw Newsgroups: net.unix-wizards Title: 4.1bsd/up.c bug Article-I.D.: rabbit.1079 Posted: Fri Jan 28 10:11:31 1983 Received: Sat Jan 29 03:12:49 1983 There is a bug in the up.c disk controller (bsd4.1) which may affect you if you run a uda-50 and at least two more unibus disks on a different controller. If one of the disks is seeking and the other tries to read but lacks some unibus resource (in ubago()), the read is left on the wrong queue. When the seek completes, the interrupt is attributed to the (unstarted read), leaving the unibus's queue a mess. The uda gets into this only because it can have several io's outstanding, and so have acquired all the buffered data paths (3 on a 750). There are two simple patches. One is for the uda never to ask for a buffered data path. The other, which I use, is to modify upustart()/up.c not to overlap seeks. The third would be to actually fix the bug. (hey berkeley?)