the attached patch fixes long scheduling latencies caused by backlog
triggered by __release_sock(). That code only executes in process
context, and we've made the backlog queue private already at this point
so it is safe to do a cond_resched_softirq().

This patch has been in the -VP patchset for some time.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

--- linux/net/core/sock.c.orig	
+++ linux/net/core/sock.c	
@@ -933,6 +933,15 @@ void __release_sock(struct sock *sk)
 
 			skb->next = NULL;
 			sk->sk_backlog_rcv(sk, skb);
+
+			/*
+			 * We are in process context here with softirqs
+			 * disabled, use cond_resched_softirq() to preempt.
+			 * This is safe to do because we've taken the backlog
+			 * queue private:
+			 */
+			cond_resched_softirq();
+
 			skb = next;
 		} while (skb != NULL);