With the inital implementation we missed to implement a skb backlog
queue . The result is that socket receive processing tossed packets.
Since AF_IUCV connections are working synchronously it leads to
connection hangs. Problems with read, close and select also occured.

Using a skb backlog queue is fixing all of these problems .

Signed-off-by: Jennifer Hunt <jenhunt@us.ibm.com>
Signed-off-by: Frank Pavlic <fpavlic@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Calling smp_call_function can lead to a deadlock if it is called
from tasklet context. 
Fixing this deadlock requires to move the smp_call_function from the
tasklet context to a work queue. To do that queue the path pending
interrupts to a separate list and move the path cleanup out of
iucv_path_sever to iucv_path_connect and iucv_path_pending.
This creates a new requirement for iucv_path_connect: it may not be
called from tasklet context anymore. 
Also fixed compile problem for CONFIG_HOTPLUG_CPU=n and
another one when walking the cpu_online mask. When doing this, 
we must disable cpu hotplug.

Signed-off-by: Frank Pavlic <fpavlic@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

From: Jennifer Hunt <jenhunt@us.ibm.com>

This patch adds AF_IUCV socket support.

Signed-off-by: Frank Pavlic <fpavlic@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Add rewritten IUCV base code to net/iucv.

Signed-off-by: Frank Pavlic <fpavlic@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>