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| author |   Johannes Berg <johannes.berg@intel.com> | 2022-04-04 11:38:47 +0200 |
|---|---|---|
| committer |   Jakub Kicinski <kuba@kernel.org> | 2022-04-05 14:28:16 -0700 |
| commit | 0b5c21bbc01e92745ca1ca4f6fd87d878fa3ea5e (patch) | |
| tree | 19ea9604000ede608a0b28759213424cd3fc4cbb /include/linux/netdevice.h | |
| parent | mlxsw: spectrum_router: simplify list unwinding (diff) | |
| download | linux-dev-0b5c21bbc01e92745ca1ca4f6fd87d878fa3ea5e.tar.xz linux-dev-0b5c21bbc01e92745ca1ca4f6fd87d878fa3ea5e.zip | |
net: ensure net_todo_list is processed quickly
In [1], Will raised a potential issue that the cfg80211 code,
which does (from a locking perspective)
rtnl_lock()
wiphy_lock()
rtnl_unlock()
might be suspectible to ABBA deadlocks, because rtnl_unlock()
calls netdev_run_todo(), which might end up calling rtnl_lock()
again, which could then deadlock (see the comment in the code
added here for the scenario).
Some back and forth and thinking ensued, but clearly this can't
happen if the net_todo_list is empty at the rtnl_unlock() here.
Clearly, the code here cannot actually put an entry on it, and
all other users of rtnl_unlock() will empty it since that will
always go through netdev_run_todo(), emptying the list.
So the only other way to get there would be to add to the list
and then unlock the RTNL without going through rtnl_unlock(),
which is only possible through __rtnl_unlock(). However, this
isn't exported and not used in many places, and none of them
seem to be able to unregister before using it.
Therefore, add a WARN_ON() in the code to ensure this invariant
won't be broken, so that the cfg80211 (or any similar) code
stays safe.
[1] https://lore.kernel.org/r/Yjzpo3TfZxtKPMAG@google.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Link: https://lore.kernel.org/r/20220404113847.0ee02e4a70da.Ic73d206e217db20fd22dcec14fe5442ca732804b@changeid
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'include/linux/netdevice.h')
| -rw-r--r-- | include/linux/netdevice.h | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 59e27a2b7bf0..b6a1e7f643da 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -3894,7 +3894,8 @@ void dev_queue_xmit_nit(struct sk_buff *skb, struct net_device *dev); extern int netdev_budget; extern unsigned int netdev_budget_usecs; -/* Called by rtnetlink.c:rtnl_unlock() */ +/* Used by rtnetlink.c:__rtnl_unlock()/rtnl_unlock() */ +extern struct list_head net_todo_list; void netdev_run_todo(void); static inline void __dev_put(struct net_device *dev) |