How to solve the Resource temporarily unavailable issue in RHEL6?

Situation:

While switching from one user to other user, getting below error. Still we have entry in limits.conf  (special case)

[root@testserver ~]#  su - testuser

su: cannot set user id: Resource temporarily unavailable

Solution:

[root@testserver ~]# cd /etc/security/limits.d/

[root@testserver limits.d]# ls -l
total 4
-rw-r--r-- 1 root root 191 Mar 23  2017 90-nproc.conf

[root@testserver limits.d]# cat 90-nproc.conf
# Default limit for number of user's processes to prevent
# accidental fork bombs.
# See rhbz #432903 for reasoning.

*            soft    nproc     1024
root       soft    nproc     unlimited

Take the backup & add the below entry

testuser    soft    nproc     327679

[root@testserver limits.d]# cp -p 90-nproc.conf 90-nproc.conf.org

[root@testserver limits.d]# cat 90-nproc.conf
# Default limit for number of user's processes to prevent
# accidental fork bombs.
# See rhbz #432903 for reasoning.

*               soft    nproc     1024
root          soft    nproc     unlimited
testuser    soft    nproc     327679

Now able to switch

root@testserver limits.d]# su - testuser

Current version is 034.008.001.001 with 10.3.6.0.170718-JDK1.7U111

-bash-4.1$

Hope it helps