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Description of problem:
When there is at least one process in the system running that has many
open file descriptors and many threads lsof -nP takes a a lot of time
to run and produces huge output.

Version-Release number of selected component (if applicable):
lsof-4.87-4.el7.x86_64

How reproducible: Always

Steps to Reproduce:
1. lsof -nP

Actual results:
Takes a long time to traverse all threads of all processes.

Expected results:
Only traverse processes, unless -K flag is given.

Created attachment 1267267 [details]
Sample program to illustrate the problem.

Created attachment 1267268 [details]
Patch to only list threads/tasks if the -K flag is given.

Example running standard and patches lsof in an EL7 desktop session:

Standard EL7 lsof:
$) time lsof -nP | wc -c
14117646

real	0m1.430s
user	0m0.648s
sys	0m0.789s
$) ./fd-and-threads &
[1] 30452
$) time lsof -nP | wc -c
75110357

real	0m13.096s
user	0m4.128s
sys	0m8.968s
$) 

Patched lsof:
$) time lsof -nP | wc -c
1748246

real	0m0.214s
user	0m0.087s
sys	0m0.131s
$) ./fd-and-threads &
[1] 31585
$) time lsof -nP | wc -c
1822372

real	0m0.247s
user	0m0.087s
sys	0m0.162s
$) time lsof -nPK | wc -c
68403949

real	0m12.946s
user	0m4.125s
sys	0m8.828s
$)

Created attachment 1399440 [details]
Proposed backport patch

Patch to ignore threads if -Ki flag is given. Change backported from upstream. lsof always displayed threads by default (documented in manpage).

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2018:3046