top: where to find process state descriptions (i.e. STATE usem)?

Dan Nelson dnelson at
Mon Feb 7 19:05:23 UTC 2011

In the last episode (Feb 07), O. Hartmann said:
> Try to find docs about the process states shown in top, but I can't find
> any hint for explanations what the abbrev.  do mean.
> I have a problem with a scientific program using OpenMP showing STATE
> 'usem' in top.  Problem: the small program is much slower on a dual or
> four core CPU using OpenMP than using only a single core (single thread
> never show state 'usem' in top).

STATEs that aren't in caps are either wait channels or mutexes, and their
initialization is scattered all over the kernel.  There isn't one
comprehensive index.  "usem" sounds like maybe a semaphore operation?  A
quick grep of the kernel doesn't show any strings starting with "usem",
though.  Maybe if you run "procstat -k <pid>" on one of those processes you
can narrow down what part of the kernel it's waiting in.

	Dan Nelson
	dnelson at

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