Hi, Had couple of questions about socket. Socket maintains few queues : Write, Receive, Error, backlog and Prequeue(tcp_opt) tcp_v4_rcv makes a decision as to where the packet needs to be tailed. What exactly is a Prequeue? <I assume that the ucopy struct of socket represents the User Space memory and is for the direct access of the user. > How is this queue used? Why is it important that the number of socket users have to be ZERO (socket_lock_t lock.users =0) for the tcp_preque to be called? When can lock.users = 0? There should be atleaset one thread which is using the socket right? Why should ucopy.task be not NULL for tcp_prequeue to process packet? If its null, it return 0 and tcp_v4_rcv, anyway calls tcp_v4_do_rcv anyway on the packets! and tcp_prequeue is doing EXACTLY the same thing...It adds the skb into prequeue and it loops till the end of the queue and calls tcp_v4_do_rcv for every member of the queue!!! And in the process_preque, why is it necessary that the ucopy.memory > socket->rcvbuf for the packets to be dequeued from Prequeue to hand it over to tcp_v4_do_rcv? And why is it important that the total headcount of Prequeue to be 1 AND ucopy.memory <= socket->rcvbuf, to wake up all threads which are sleeping on 'listen' call? If there is one thread for the socket(lock.users), then tcp_prequeue wont be called from tcp_v4_rcv. Then, how can it wake up all the threads in the sleep queue through wake_up_interruptable(sock->sleep)? Please explain. Any help with explanation of tcp_prequeue and the different queues like Prequeue and backlog queue will be greatly appreciated. Thank you for time and effort. Regards, Anu -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ IRC Channel: irc.openprojects.net / #kernelnewbies Web Page: http://www.kernelnewbies.org/
