John Hall wrote: > John Hall wrote: > > > I think you'll find that the JCB is only updated when a task > > switch occurs... > > > > When a TRAP#n is executed, the PC and SP are saved on the > > supervisor stack, hence WL's earlier comment... > > Oops! PC and SR, of course :-) > > In supervisor mode, the job's SP is in the USP... > > > > Now I can forsee there might be a problem if the calling job is > > > in SV mode when it makes the Open call, as it would first have > > > to exit SV mode before it could set up jobs, open channels and > > > things, but it must sooner or later exit that mode, and the > > > execution will procede as described. > > > > This is wrong, for the above reason. > > Correction. This would work, so long as the job's PC could be found > on the supervisor stack by the driver code...
...which, of course, it couldn't if the job had entered supervisor mode via TRAP#0 :-( (Time to stop talking to myself and have a beer, I think!) John _______________________________________________ QL-Users Mailing List http://www.q-v-d.demon.co.uk/smsqe.htm
