sfc: Remove rcu_read_lock() around XDP program invocation
authorToke Høiland-Jørgensen <toke@redhat.com>
Thu, 24 Jun 2021 16:06:06 +0000 (18:06 +0200)
committerDaniel Borkmann <daniel@iogearbox.net>
Thu, 24 Jun 2021 17:46:01 +0000 (19:46 +0200)
commit4eb14e3fc6197b7205069ed4e2b31eafa11a0697
treea31ac8a2c2aa564c0f4f781edbc83aeeff7ed2e9
parent4415db6ca85ae57830a83290388f2b9dfa5f237f
sfc: Remove rcu_read_lock() around XDP program invocation

The sfc driver has rcu_read_lock()/rcu_read_unlock() pairs around XDP
program invocations. However, the actual lifetime of the objects referred
by the XDP program invocation is longer, all the way through to the call to
xdp_do_flush(), making the scope of the rcu_read_lock() too small. This
turns out to be harmless because it all happens in a single NAPI poll
cycle (and thus under local_bh_disable()), but it makes the rcu_read_lock()
misleading.

Rather than extend the scope of the rcu_read_lock(), just get rid of it
entirely. With the addition of RCU annotations to the XDP_REDIRECT map
types that take bh execution into account, lockdep even understands this to
be safe, so there's really no reason to keep it around.

Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Edward Cree <ecree.xilinx@gmail.com>
Cc: Martin Habets <habetsm.xilinx@gmail.com>
Link: https://lore.kernel.org/bpf/20210624160609.292325-17-toke@redhat.com
drivers/net/ethernet/sfc/rx.c