@@ -1160,6 +1160,20 @@ static int rx_queue_add_kobject(struct net_device *dev, int index)
struct kobject *kobj = &queue->kobj;
int error = 0;
+ /* Rx queues are cleared in rx_queue_release to allow later
+ * re-registration. This is triggered when their kobj refcount is
+ * dropped.
+ *
+ * If a queue is removed while both a read (or write) operation and a
+ * the re-addition of the same queue are pending (waiting on rntl_lock)
+ * it might happen that the re-addition will execute before the read,
+ * making the initial removal to never happen (queue's kobj refcount
+ * won't drop enough because of the pending read). In such rare case,
+ * return to allow the removal operation to complete.
+ */
+ if (unlikely(kobj->state_initialized))
+ return -EAGAIN;
+
/* Kobject_put later will trigger rx_queue_release call which
* decreases dev refcount: Take that reference here
*/
@@ -1775,6 +1789,20 @@ static int netdev_queue_add_kobject(struct net_device *dev, int index)
struct kobject *kobj = &queue->kobj;
int error = 0;
+ /* Tx queues are cleared in netdev_queue_release to allow later
+ * re-registration. This is triggered when their kobj refcount is
+ * dropped.
+ *
+ * If a queue is removed while both a read (or write) operation and a
+ * the re-addition of the same queue are pending (waiting on rntl_lock)
+ * it might happen that the re-addition will execute before the read,
+ * making the initial removal to never happen (queue's kobj refcount
+ * won't drop enough because of the pending read). In such rare case,
+ * return to allow the removal operation to complete.
+ */
+ if (unlikely(kobj->state_initialized))
+ return -EAGAIN;
+
/* Kobject_put later will trigger netdev_queue_release call
* which decreases dev refcount: Take that reference here
*/
With the (upcoming) removal of the rtnl_trylock/restart_syscall logic and because of how Tx/Rx queues are implemented (and their requirements), it might happen that a queue is re-added before having the chance to be cleared. In such rare case, do not complete the queue addition operation. Signed-off-by: Antoine Tenart <atenart@kernel.org> --- net/core/net-sysfs.c | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+)