On 2/11/26 20:18, Petr Oros wrote:
Three driver callbacks schedule a reset and wait for its completion: ndo_change_mtu(), ethtool set_ringparam(), and ethtool set_channels().Waiting for reset in ndo_change_mtu() and set_ringparam() was added by commit c2ed2403f12c ("iavf: Wait for reset in callbacks which trigger it") to fix a race condition where adding an interface to bonding immediately after MTU or ring parameter change failed because the interface was still in __RESETTING state. The same commit also added waiting in iavf_set_priv_flags(), which was later removed by commit 53844673d555 ("iavf: kill "legacy-rx" for good"). Waiting in set_channels() was introduced earlier by commit 4e5e6b5d9d13 ("iavf: Fix return of set the new channel count") to ensure the PF has enough time to complete the VF reset when changing channel count, and to return correct error codes to userspace. Commit ef490bbb2267 ("iavf: Add net_shaper_ops support") added net_shaper_ops to iavf, which required reset_task to use _locked NAPI variants (napi_enable_locked, napi_disable_locked) that need the netdev instance lock. Later, commit 7e4d784f5810 ("net: hold netdev instance lock during rtnetlink operations") and commit 2bcf4772e45a ("net: ethtool: try to protect all callback with netdev instance lock") started holding the netdev instance lock during ndo and ethtool callbacks for drivers with net_shaper_ops. Finally, commit 120f28a6f314 ("iavf: get rid of the crit lock") replaced the driver's crit_lock with netdev_lock in reset_task, causing incorrect behavior: the callback holds netdev_lock and waits for reset_task, but reset_task needs the same lock: Thread 1 (callback) Thread 2 (reset_task) ------------------- --------------------- netdev_lock() [blocked on workqueue] ndo_change_mtu() or ethtool op iavf_schedule_reset() iavf_wait_for_reset() iavf_reset_task() waiting... netdev_lock() <- blocked This does not strictly deadlock because iavf_wait_for_reset() uses wait_event_interruptible_timeout() with a 5-second timeout. The wait eventually times out, the callback returns an error to userspace, and after the lock is released reset_task completes the reset. This leads to incorrect behavior: userspace sees an error even though the configuration change silently takes effect after the timeout. Fix this by extracting the reset logic from iavf_reset_task() into a new iavf_reset_step() function that expects netdev_lock to be already held. The three callbacks now call iavf_reset_step() directly instead of scheduling the work and waiting, performing the reset synchronously in the caller's context which already holds netdev_lock. This eliminates both the incorrect error reporting and the need for iavf_wait_for_reset(), which is removed along with the now-unused reset_waitqueue. The workqueue-based iavf_reset_task() becomes a thin wrapper that acquires netdev_lock and calls iavf_reset_step(), preserving its use for PF-initiated resets. The callbacks may block for several seconds while iavf_reset_step() polls hardware registers, but this is acceptable since netdev_lock is a per-device mutex and only serializes operations on the same interface. v3: - Remove netif_running() guard from iavf_set_channels(). Unlike set_ringparam where descriptor counts are picked up by iavf_open() directly, num_req_queues is only consumed during iavf_reinit_interrupt_scheme() in the reset path. Skipping the reset on a down device would silently discard the channel count change. - Remove dead reset_waitqueue code (struct field, init, and all wake_up calls) since iavf_wait_for_reset() was the only consumer. Fixes: 120f28a6f314 ("iavf: get rid of the crit lock") Reviewed-by: Jacob Keller <[email protected]> Signed-off-by: Petr Oros <[email protected]> --- drivers/net/ethernet/intel/iavf/iavf.h | 3 +- .../net/ethernet/intel/iavf/iavf_ethtool.c | 19 ++--- drivers/net/ethernet/intel/iavf/iavf_main.c | 77 ++++++------------- .../net/ethernet/intel/iavf/iavf_virtchnl.c | 1 - 4 files changed, 31 insertions(+), 69 deletions(-)
thank you for improving on your v2, next time please post as top-level (instead of In-reply-to), to get more traction earlier Reviewed-by: Przemek Kitszel <[email protected]>
