On Fri, Aug 08, 2025 at 05:12:05PM -0700, Jakub Kicinski wrote:
> The following order of calls currently deadlocks if:
> - device has threaded=1; and
> - NAPI has persistent config with threaded=0.
>
> netif_napi_add_weight_config()
> dev->threaded == 1
> napi_kthread_create()
>
> napi_enable()
> napi_restore_config()
> napi_set_threaded(0)
> napi_stop_kthread()
> while (NAPIF_STATE_SCHED)
> msleep(20)
>
> We deadlock because disabled NAPI has STATE_SCHED set.
> Creating a thread in netif_napi_add() just to destroy it in
> napi_disable() is fairly ugly in the first place. Let's read
> both the device config and the NAPI config in netif_napi_add().
>
> Fixes: e6d76268813d ("net: Update threaded state in napi config in
> netif_set_threaded")
> Signed-off-by: Jakub Kicinski <k...@kernel.org>
> ---
> net/core/dev.h | 8 ++++++++
> net/core/dev.c | 5 +++--
> 2 files changed, 11 insertions(+), 2 deletions(-)
>
Reviewed-by: Joe Damato <j...@dama.to>
