Stopped processes with negative priority

[Barry Margolin]

>From time to time I notice stopped processes with negative priority
(perhaps always -5, in case this is significant) on our Sun-4's (running
SunOS 4.1.1, but I think I remember seeing this in earlier SunOS releases
as well).  I generally notice it because any process with a negative
priority is included in the load average, and the load sometimes gets
pinned at 1.5-2 even though no processes are running hard.  If I send the
process a SIGCONT it immediately stops again, but this time with a positive
priority, so the load goes down to a reasonable level.

I suspect that the problem may be a kernel race condition.  The processes
in this state always seem to be full screen programs.  I suspect what's
happening is that the program catches SIGTSTP, resets tty modes, and then
sends itself a SIGSTOP to stop itself for real.  Maybe the process is being
stopped before the kernel has restored the priority.

Is this indicative of a real problem?  Are these processes using any more
system resources than ordinary stopped processes?  If they're counted in
the load average, then I assume this means that they're sitting on the
active process queue, so are they increasing the scheduler overhead?
-- 
Barry Margolin, Thinking Machines Corp.

barmar at think.com
{uunet,harvard}!think!barmar