EINVALThe value that was passed in the epoll event length parameter is invalid. ENFILEEPOLLPRI or EPOLLONESHOT cannot be specified with EPOLLEXCLUSIVE. ENFILEAn epoll file cannot be watched exclusively. EINFILEA file is either being modified or is already exclusively watched. ...
In kernel versions before 2.6.9, the EPOLL_CTL_DEL operation required a non-null pointer in event, even though this argument is ignored. Since Linux 2.6.9, event can be specified as NULL when using EPOLL_CTL_DEL. Applications that need to be portable to kernels before 2.6.9 should specif...