[AF_IUCV]: Avoid deadlock between iucv_path_connect and tasklet.
An iucv deadlock may occur, where one CPU is spinning on the
iucv_table_lock for iucv_tasklet_fn(), while another CPU is holding
the iucv_table_lock for an iucv_path_connect() and is waiting for
the first CPU in an smp_call_function.
Solution: replace spin_lock in iucv_tasklet_fn by spin_trylock and
reschedule tasklet in case of non-granted lock.
Signed-off-by: Ursula Braun <braunu@de.ibm.com>
Acked-by: Frank Pavlic <fpavlic@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/iucv/iucv.c b/net/iucv/iucv.c
index b733306..ad5150b 100644
--- a/net/iucv/iucv.c
+++ b/net/iucv/iucv.c
@@ -1494,7 +1494,10 @@
struct iucv_irq_list *p, *n;
/* Serialize tasklet, iucv_path_sever and iucv_path_connect. */
- spin_lock(&iucv_table_lock);
+ if (!spin_trylock(&iucv_table_lock)) {
+ tasklet_schedule(&iucv_tasklet);
+ return;
+ }
iucv_active_cpu = smp_processor_id();
spin_lock_irq(&iucv_queue_lock);