Re: [PATCH] batman-adv: Avoid double-rtnl_lock ELP metric worker

[Sven Eckelmann <sven@narfation.org>]

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On Monday, 16 February 2026 20:05:55 CET Sven Eckelmann wrote:
> batadv_v_elp_get_throughput() might be called when the RTNL lock is already
> held. This could be problematic when the work queue item is canceled via
> cancel_delayed_work_sync() in batadv_v_elp_iface_disable(). In this case,
> an rtnl_lock() would cause a deadlock.
> 
> To avoid this, rtnl_trylock() was used in this function to skip the
> retrieval of the ethtool information in case the RTNL lock was already
> held.
> 
> But for cfg80211 interfaces, batadv_get_real_netdev() was called - which
> also uses rtnl_lock(). The approach for __ethtool_get_link_ksettings() must
> also be used instead and the lockless version __batadv_get_real_netdev()
> has to called.
> 
> Fixes: 405d49a20a20 ("batman-adv: Drop unmanaged ELP metric worker")
> Signed-off-by: Sven Eckelmann <sven@narfation.org>
> ---
>  net/batman-adv/bat_v_elp.c      | 10 +++++++++-
>  net/batman-adv/hard-interface.c |  8 ++++----
>  net/batman-adv/hard-interface.h |  1 +
>  3 files changed, 14 insertions(+), 5 deletions(-)


Via github [1]:

Reported-by: Christian Schmidbauer <github@grische.xyz>
Tested-by: Sören Skaarup <freifunk_nordm4nn@gmx.de>

Regards,
	Sven

[1] https://github.com/freifunkMUC/site-ffm/issues/776#issuecomment-3920865984

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