[PATCH net-next 1/2] net: transition netdev reg state earlier in run_todo

In prep for unregistering netdevs out of order move the netdev
state validation and change outside of the loop.

While at it modernize this code and use WARN() instead of
pr_err() + dump_stack().

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 net/core/dev.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 909fb3815910..2749776e2dd2 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c

@@ -9906,6 +9906,7 @@ static void netdev_wait_allrefs(struct net_device *dev)
  */
 void netdev_run_todo(void)
 {
+       struct net_device *dev, *tmp;
        struct list_head list;
 #ifdef CONFIG_LOCKDEP
        struct list_head unlink_list;

@@ -9926,24 +9927,23 @@ void netdev_run_todo(void)

        __rtnl_unlock();

-
        /* Wait for rcu callbacks to finish before next phase */
        if (!list_empty(&list))
                rcu_barrier();

-       while (!list_empty(&list)) {
-               struct net_device *dev
-                       = list_first_entry(&list, struct net_device, todo_list);
-               list_del(&dev->todo_list);
-
+       list_for_each_entry_safe(dev, tmp, &list, todo_list) {
                if (unlikely(dev->reg_state != NETREG_UNREGISTERING)) {
-                       pr_err("network todo '%s' but state %d\n",
-                              dev->name, dev->reg_state);
-                       dump_stack();
+                       netdev_WARN(dev, "run_todo but not unregistering\n");
+                       list_del(&dev->todo_list);
                        continue;
                }

                dev->reg_state = NETREG_UNREGISTERED;
+       }
+
+       while (!list_empty(&list)) {
+               dev = list_first_entry(&list, struct net_device, todo_list);
+               list_del(&dev->todo_list);

                netdev_wait_allrefs(dev);

--

2.34.1

Sprinkle for each loops to allow netdevices to be unregistered
out of order, as their refs are released.

This prevents problems caused by dependencies between netdevs
which want to release references in their ->priv_destructor.
See commit d6ff94afd90b ("vlan: move dev_put into vlan_dev_uninit")
for example.

Eric has removed the only known ordering requirement in
commit c002496babfd ("Merge branch 'ipv6-loopback'")
so let's try this and see if anything explodes...

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 net/core/dev.c | 64 +++++++++++++++++++++++++++++---------------------
 1 file changed, 37 insertions(+), 27 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 2749776e2dd2..05fa867f1878 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c

@@ -9811,8 +9811,8 @@ int netdev_unregister_timeout_secs __read_mostly = 10;
 #define WAIT_REFS_MIN_MSECS 1
 #define WAIT_REFS_MAX_MSECS 250
 /**
- * netdev_wait_allrefs - wait until all references are gone.
- * @dev: target net_device
+ * netdev_wait_allrefs_any - wait until all references are gone.
+ * @list: list of net_devices to wait on
  *
  * This is called when unregistering network devices.
  *

@@ -9822,37 +9822,45 @@ int netdev_unregister_timeout_secs __read_mostly = 10;
  * We can get stuck here if buggy protocols don't correctly
  * call dev_put.
  */
-static void netdev_wait_allrefs(struct net_device *dev)
+static struct net_device *netdev_wait_allrefs_any(struct list_head *list)
 {
        unsigned long rebroadcast_time, warning_time;
-       int wait = 0, refcnt;
+       struct net_device *dev;
+       int wait = 0;

-       linkwatch_forget_dev(dev);
+       list_for_each_entry(dev, list, todo_list)
+               linkwatch_forget_dev(dev);

        rebroadcast_time = warning_time = jiffies;
-       refcnt = netdev_refcnt_read(dev);

-       while (refcnt != 1) {
+       list_for_each_entry(dev, list, todo_list)
+               if (netdev_refcnt_read(dev) == 1)
+                       return dev;
+
+       while (true) {
                if (time_after(jiffies, rebroadcast_time + 1 * HZ)) {
                        rtnl_lock();

                        /* Rebroadcast unregister notification */
-                       call_netdevice_notifiers(NETDEV_UNREGISTER, dev);
+                       list_for_each_entry(dev, list, todo_list)
+                               call_netdevice_notifiers(NETDEV_UNREGISTER, dev);

                        __rtnl_unlock();
                        rcu_barrier();
                        rtnl_lock();

-                       if (test_bit(__LINK_STATE_LINKWATCH_PENDING,
-                                    &dev->state)) {
-                               /* We must not have linkwatch events
-                                * pending on unregister. If this
-                                * happens, we simply run the queue
-                                * unscheduled, resulting in a noop
-                                * for this device.
-                                */
-                               linkwatch_run_queue();
-                       }
+                       list_for_each_entry(dev, list, todo_list)
+                               if (test_bit(__LINK_STATE_LINKWATCH_PENDING,
+                                            &dev->state)) {
+                                       /* We must not have linkwatch events
+                                        * pending on unregister. If this
+                                        * happens, we simply run the queue
+                                        * unscheduled, resulting in a noop
+                                        * for this device.
+                                        */
+                                       linkwatch_run_queue();
+                                       break;
+                               }

                        __rtnl_unlock();

@@ -9867,14 +9875,18 @@ static void netdev_wait_allrefs(struct net_device *dev)
                        wait = min(wait << 1, WAIT_REFS_MAX_MSECS);
                }

-               refcnt = netdev_refcnt_read(dev);
+               list_for_each_entry(dev, list, todo_list)
+                       if (netdev_refcnt_read(dev) == 1)
+                               return dev;

-               if (refcnt != 1 &&
-                   time_after(jiffies, warning_time +
+               if (time_after(jiffies, warning_time +
                               netdev_unregister_timeout_secs * HZ)) {
-                       pr_emerg("unregister_netdevice: waiting for %s to become free. Usage count = %d\n",
-                                dev->name, refcnt);
-                       ref_tracker_dir_print(&dev->refcnt_tracker, 10);
+                       list_for_each_entry(dev, list, todo_list) {
+                               pr_emerg("unregister_netdevice: waiting for %s to become free. Usage count = %d\n",
+                                        dev->name, netdev_refcnt_read(dev));
+                               ref_tracker_dir_print(&dev->refcnt_tracker, 10);
+                       }
+
                        warning_time = jiffies;
                }
        }

@@ -9942,11 +9954,9 @@ void netdev_run_todo(void)
        }

        while (!list_empty(&list)) {
-               dev = list_first_entry(&list, struct net_device, todo_list);
+               dev = netdev_wait_allrefs_any(&list);
                list_del(&dev->todo_list);

-               netdev_wait_allrefs(dev);
-
                /* paranoia */
                BUG_ON(netdev_refcnt_read(dev) != 1);
                BUG_ON(!list_empty(&dev->ptype_all));
--

2.34.1

Sprinkle for each loops to allow netdevices to be unregistered
out of order, as their refs are released.

This prevents problems caused by dependencies between netdevs
which want to release references in their ->priv_destructor.
See commit d6ff94afd90b ("vlan: move dev_put into vlan_dev_uninit")
for example.

Eric has removed the only known ordering requirement in
commit c002496babfd ("Merge branch 'ipv6-loopback'")
so let's try this and see if anything explodes...

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 net/core/dev.c | 64 +++++++++++++++++++++++++++++---------------------
 1 file changed, 37 insertions(+), 27 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 2749776e2dd2..05fa867f1878 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c

@@ -9811,8 +9811,8 @@ int netdev_unregister_timeout_secs __read_mostly = 10;
 #define WAIT_REFS_MIN_MSECS 1
 #define WAIT_REFS_MAX_MSECS 250
 /**
- * netdev_wait_allrefs - wait until all references are gone.
- * @dev: target net_device
+ * netdev_wait_allrefs_any - wait until all references are gone.
+ * @list: list of net_devices to wait on
  *
  * This is called when unregistering network devices.
  *

@@ -9822,37 +9822,45 @@ int netdev_unregister_timeout_secs __read_mostly = 10;
  * We can get stuck here if buggy protocols don't correctly
  * call dev_put.
  */
-static void netdev_wait_allrefs(struct net_device *dev)
+static struct net_device *netdev_wait_allrefs_any(struct list_head *list)
 {
        unsigned long rebroadcast_time, warning_time;
-       int wait = 0, refcnt;
+       struct net_device *dev;
+       int wait = 0;

-       linkwatch_forget_dev(dev);