I resolved this problem from these steps:
1) restarting your EC2 instance.
2) sudo service httpd restart
3) sudo chown -R mysql:mysql /var/lib/mysql
4) Change the innodb_buffer_pool_size option inside /etc/my.cnf from 128 (can be different) to 500M. If you have not innodb_buffer_pool_size option in your /etc/my.cnf, add innodb_buffer_pool_size=500M in [mysqld] section.