RLIMIT_SIGPENDING (since Linux 2.6.8)
Specifies the limit on the number of signals that may be queued for the real user ID of the calling process. Both standard and real-time signals are counted for the purpose
of checking this limit. However, the limit is enforced only for sigqueue(3); it is always possible to use kill(2) to queue one instance of any of the signals that are not
already queued to the process.
to get over this: