id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
249	"Random ""Unexpected IOM status"" messages in ci-kit ""psl -syserr"""	canthony	Eric Swenson	"
{{{
03:09:28 1000135  5 disk_control: Unexpected IOM status 400000000000000000000000 for dska (channel A11).
}}}

The number and timing of the messages vary from run to run, suggesting a race condition.

Running ci-kit in a single CPU configuration results in no messages, suggesting that the race condition is in Multics and not the simulator.

The message is generated by procedure check_stat in disk_control.pl1. check_stat is called by two procedures: ""run"" and ""disk_inter"".

The ""run"" procedure contains the comment:

{{{
/* Poll for disk completion.  This is required for allocation lock checks, and
   during run_locks from page control, since both are run masked, and this
   polling is the only way we would see disk completion.  This race hazard
   on normal 15-seconds run_locks will produce some interrupts without
   terminate status, but you can't win them all.  It may also produce some
   situations of interrupt wile not active. */
}}}

It is not known that this is the source of the message."	defect	new	minor		Hardcore