From: Jakub Kicinski Date: Tue, 9 Jun 2026 17:13:08 +0000 (-0700) Subject: Merge branch 'net-ethtool-let-ops-locked-drivers-run-without-rtnl_lock' X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3abbe30231441f1fbb3305e9854c56a34650af53;p=thirdparty%2Flinux.git Merge branch 'net-ethtool-let-ops-locked-drivers-run-without-rtnl_lock' Jakub Kicinski says: ==================== net: ethtool: let ops locked drivers run without rtnl_lock With the ethtool_get_link_ksettings() situation hopefully ironed out the previous series (commit 6a5d837f0ce2) let's return to the main part of the series. We have been slowly moving towards removing the rtnl_lock dependency in driver ops since the concept of "ops-locked" drivers have been introduced last year. Since last year will take the netdev instance lock before invoking any ndo or ethtool op of "ops-locked" drivers. We dipped our toes into rtnl_lock-less ops with the queue binding API. Queue stats, NAPI, and other netdev-netlink objects are also queried without holding rtnl_lock already. It's time to take the next logical step and lift the requirement from ethtool ops. The direct motivation for this patchset is that ethtool ops often involve communicating with device FW, and may take a long time to complete. Aggressive polling of device state on machines with 10+ NICs have been shown to significantly increase rtnl_lock pressure. There's a handful of areas which still need rtnl_lock (see below). I decided to convert everything to rtnl_lock-less by default, and add a set of flags which let the drivers request rtnl_lock to still be taken. I don't love this, but I'm worried that opt-in would be even more confusing. Known issues / exclusions: - qdiscs - qdisc configuration currently assumes rtnl_lock, this is mostly impacting set_channels callback. qdisc config is probably the easiest one of the exclusions to tackle, it's fairly self-contained. - features - even tho feature changes are (correctly) plumbed to the driver thru ndos they are part of ethtool uAPI. ethtool itself calls netdev_features_change() if it has spotted device feature change before vs after to the callback. Some drivers also call netdev_features_change() directly in response to various changes, e.g. setting priv flags. Since features have to propagate to upper and lower devices anything that touches features is quite hard to move from under rtnl_lock. - phylink - phylink and SFP depend on rtnl_lock today, I suspect that this is purely for historic reasons. I started poking at it and don't really see a need for a global lock. But accessing the netdev instance lock from the SFP entry points will require some attention from the phylink folks. - phydev - similar to phylink, looks quite doable. But no ops-locked driver currently has a phydev (fbnic only uses phylink) so phydev related paths retain a ASSERT_RTNL() for now. Tested on mlx5, bnxt and fbnic. ==================== Link: https://patch.msgid.link/20260605002912.3456868-1-kuba@kernel.org Signed-off-by: Jakub Kicinski --- 3abbe30231441f1fbb3305e9854c56a34650af53