ifb: fix rcu_sched self-detected stalls

[ Upstream commit 440d57b ]

According to the commit 16b0dc2
(dummy: fix rcu_sched self-detected stalls)

Eric Dumazet fix the problem in dummy, but the ifb will occur the
same problem like the dummy modules.

Trying to "modprobe ifb numifbs=30000" triggers :

INFO: rcu_sched self-detected stall on CPU

After this splat, RTNL is locked and reboot is needed.

We must call cond_resched() to avoid this, even holding RTNL.

Signed-off-by: Ding Tianhong <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

drivers/net/ifb.c

@@ -33,6 +33,7 @@
 #include <linux/etherdevice.h>
 #include <linux/init.h>
 #include <linux/moduleparam.h>
+#include <linux/sched.h>
 #include <net/pkt_sched.h>
 #include <net/net_namespace.h>
 
@@ -252,8 +253,10 @@ static int __init ifb_init_module(void)
 	rtnl_lock();
 	err = __rtnl_link_register(&ifb_link_ops);
 
-	for (i = 0; i < numifbs && !err; i++)
+	for (i = 0; i < numifbs && !err; i++) {
 		err = ifb_init_one(i);
+		cond_resched();
+	}
 	if (err)
 		__rtnl_link_unregister(&ifb_link_ops);
 	rtnl_unlock();