netdev, sched/wait: Fix sleeping inside wait event

rtnl_lock_unregistering*() take rtnl_lock() -- a mutex -- inside a
wait loop. The wait loop relies on current->state to function, but so
does mutex_lock(), nesting them makes for the inner to destroy the
outer state.

Fix this using the new wait_woken() bits.

Reported-by: Fengguang Wu <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Acked-by: David S. Miller <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Cong Wang <[email protected]>
Cc: David Gibson <[email protected]>
Cc: Eric Biederman <[email protected]>
Cc: Eric Dumazet <[email protected]>
Cc: Jamal Hadi Salim <[email protected]>
Cc: Jerry Chu <[email protected]>
Cc: Jiri Pirko <[email protected]>
Cc: John Fastabend <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Nicolas Dichtel <[email protected]>
Cc: [email protected] <[email protected]>
Cc: stephen hemminger <[email protected]>
Cc: Tom Gundersen <[email protected]>
Cc: Tom Herbert <[email protected]>
Cc: Veaceslav Falico <[email protected]>
Cc: Vlad Yasevich <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

Author: Peter Zijlstra

net/core/dev.c

@@ -7196,11 +7196,10 @@ static void __net_exit rtnl_lock_unregistering(struct list_head *net_list)
 	 */
 	struct net *net;
 	bool unregistering;
-	DEFINE_WAIT(wait);
+	DEFINE_WAIT_FUNC(wait, woken_wake_function);
 
+	add_wait_queue(&netdev_unregistering_wq, &wait);
 	for (;;) {
-		prepare_to_wait(&netdev_unregistering_wq, &wait,
-				TASK_UNINTERRUPTIBLE);
 		unregistering = false;
 		rtnl_lock();
 		list_for_each_entry(net, net_list, exit_list) {
@@ -7212,9 +7211,10 @@ static void __net_exit rtnl_lock_unregistering(struct list_head *net_list)
 		if (!unregistering)
 			break;
 		__rtnl_unlock();
-		schedule();
+
+		wait_woken(&wait, TASK_UNINTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
 	}
-	finish_wait(&netdev_unregistering_wq, &wait);
+	remove_wait_queue(&netdev_unregistering_wq, &wait);
 }
 
 static void __net_exit default_device_exit_batch(struct list_head *net_list)

net/core/rtnetlink.c

@@ -365,11 +365,10 @@ static void rtnl_lock_unregistering_all(void)
 {
 	struct net *net;
 	bool unregistering;
-	DEFINE_WAIT(wait);
+	DEFINE_WAIT_FUNC(wait, woken_wake_function);
 
+	add_wait_queue(&netdev_unregistering_wq, &wait);
 	for (;;) {
-		prepare_to_wait(&netdev_unregistering_wq, &wait,
-				TASK_UNINTERRUPTIBLE);
 		unregistering = false;
 		rtnl_lock();
 		for_each_net(net) {
@@ -381,9 +380,10 @@ static void rtnl_lock_unregistering_all(void)
 		if (!unregistering)
 			break;
 		__rtnl_unlock();
-		schedule();
+
+		wait_woken(&wait, TASK_UNINTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
 	}
-	finish_wait(&netdev_unregistering_wq, &wait);
+	remove_wait_queue(&netdev_unregistering_wq, &wait);
 }
 
 /**