On Wed, 03 Jun 2015 12:42:28 +0200, Grzegorz Dwornicki said:

Server callend the recv function and waits for the data from client soo its blocked in wait_queue. The socket is in nonblocking state. Can this proces/thread be unblocked on demand?

Umm... according to the manpage for 'man 2 recv': If no messages are available at the socket, the receive calls wait for a message to arrive, unless the socket is nonblocking (see fcntl(2)), in which case the value -1 is returned and the external variable errno is set to EAGAIN or EWOULDBLOCK. The receive calls normally return any data available, up to the requested amount, rather than waiting for receipt of the full amount requested. So if the socket really *is* nonblocking, I'm not seeing how it would end up blocked. If it sits in that state for long enough, you might want to do a 'cat /proc/NNN/stack' to see where in the kernel it is. But first, I'd double check that the socket is in fact non-blocking. Did you remember to do something like this: rc = socket(AF_INET,SOCK_whatever|SOCK_NONBLOCK,protocol); if (rc < 0) { /* whine about failure */ };