tree 16fc7bc990fa47cccb62bdb34cb23bd3c26b7a50
parent cfc1fbb079b265bf69d4ceba590a2e2c1a1cde33
author Eric Dumazet <eric.dumazet@gmail.com> 1272490548 -0700
committer David S. Miller <davem@davemloft.net> 1272490548 -0700

net: speedup udp receive path

Since commit 95766fff ([UDP]: Add memory accounting.), 
each received packet needs one extra sock_lock()/sock_release() pair.

This added latency because of possible backlog handling. Then later,
ticket spinlocks added yet another latency source in case of DDOS.

This patch introduces lock_sock_bh() and unlock_sock_bh()
synchronization primitives, avoiding one atomic operation and backlog
processing.

skb_free_datagram_locked() uses them instead of full blown
lock_sock()/release_sock(). skb is orphaned inside locked section for
proper socket memory reclaim, and finally freed outside of it.

UDP receive path now take the socket spinlock only once.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>