Can't create threads in threadpool (errno=11)

Hello all,

I am running a RHEL 6.4 server with 10.0.14-MariaDB having 67G of RAM.

Often i am getting error in the mysqld.log file as,
141209 17:27:19 [ERROR] Can't create threads in threadpool (errno=11).
141209 17:27:19 [Note] Threadpool has been blocked for 32 seconds

i have googled this,some suggessted to change the limits in /etc/security/limits.conf.i did as below.
mysql soft nofile 10240
mysql hard nofile 40960
mysql soft nproc 10240
mysql hard nproc 40960
even i have changed the threads and max connections as below:
thread_pool_max_threads 4000

On shell if i type $perror 11, it shows "OS error code 11: Resource temporarily unavailable"
please help me.what i have to do.it increases the server load.

Thanks in advance.