Question: yep, i know that question was asked many times, but unfortunately i didn't find the complete answer on it.

so, how to limit the number of simultaneous processes per user?

i found two solutions:

1. using pam\_limits. in that case i need to configure /etc/security/limits.conf file. unfortunately, this solution works only for pam aware applications, that is it's not universal.
2. using ulimit called from $HOME/profile. unfortunately it doens't work in all cases too. i tried to set "ulimit -u 100" and then launched in the same shell "stress --vm 200 --vm--bytes 100". application was successfully launched and i got more than 200 processes under user root.

i need to build a robust system, so solutions which work only in some cases are inappropriate.

Answer: 
A kernel security patch [grsecurity](http://grsecurity.net/) has a feature called `Enforce RLMIT_NPROC on execs`. When enabled, it enforces per-user limits to be system-wide instead of per-login (or worse, as you have observed).
You can set up limits in `/etc/security/limits.conf`