Removing entries from cpumap and devmap, goes through a number of
syncronization steps to make sure no new xdp_frames can be enqueued.
But there is a small chance, that xdp_frames remains which have not
been flushed/processed yet. Flushing these during teardown, happens
from RCU context and not as usual under RX NAPI context.
The optimization introduced in commt 389ab7f01af9 ("xdp: introduce
xdp_return_frame_rx_napi"), missed that the flush operation can also
be called from RCU context. Thus, we cannot always use the
xdp_return_frame_rx_napi call, which take advantage of the protection
provided by XDP RX running under NAPI protection.
The samples/bpf xdp_redirect_cpu have a --stress-mode, that is
adjusted to easier reproduce (verified by Red Hat QA).
---
Jesper Dangaard Brouer (3):
xdp: fix bug in cpumap teardown code path
samples/bpf: xdp_redirect_cpu adjustment to reproduce teardown race easier
xdp: fix bug in devmap teardown code path
kernel/bpf/cpumap.c | 15 +++++++++------
kernel/bpf/devmap.c | 14 +++++++++-----
samples/bpf/xdp_redirect_cpu_kern.c | 2 +-
samples/bpf/xdp_redirect_cpu_user.c | 4 ++--
4 files changed, 21 insertions(+), 14 deletions(-)
--
