net/i40e: Fix concurrency issues between config flow and XSK
Use synchronize_rcu to wait until the XSK wakeup function finishes before destroying the resources it uses: 1. i40e_down already calls synchronize_rcu. On i40e_down either __I40E_VSI_DOWN or __I40E_CONFIG_BUSY is set. Check the latter in i40e_xsk_wakeup (the former is already checked there). 2. After switching the XDP program, call synchronize_rcu to let i40e_xsk_wakeup exit before the XDP program is freed. 3. Changing the number of channels brings the interface down (see i40e_prep_for_reset and i40e_pf_quiesce_all_vsi). 4. Disabling UMEM sets __I40E_CONFIG_BUSY, too. Signed-off-by:Maxim Mikityanskiy <maximmi@mellanox.com> Signed-off-by:
Björn Töpel <bjorn.topel@intel.com> Signed-off-by:
Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20191217162023.16011-4-maximmi@mellanox.com
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