id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
224	Fix Scheduler for Procs Required	Eric Swenson	Eric Swenson	"The  scheduler  (pxss.alm)  has  a  bug  whereby  it  can  preempt  the  wrong  process  when  a  ready-to-run process has limited the set of processors it can run on. When a waiting process is notified that it can run again, the scheduler searches for a process to preempt. However, it doesn’t take into account the fact that the processor on which a candidate process is running might not be in the set of processors to which the now-ready process is restricted. It chooses the first running process to preempt, and once it has preempted it, it considers its task done. When the scheduler attempts to find a process to schedule on the preempted process’ processor, it cannot schedule the ready process on this processor, so another process is scheduled. If no such process can be found, the idle process for this processor is chosen. The now-ready process must wait  until  to  be  scheduled,  while  some  process  running  on  one  of  its  limited  set  of  CPUs  exhausts  its quantum.

The ticket is described in detail in: https://s3.amazonaws.com/eswenson-multics/public/mcrs/MCR10054.pdf"	defect	closed	major	MR12.7	Hardcore	MR12.6e	fixed