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thunderx: Remove rcu_read_lock() around XDP program invocation

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The thunderx 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>
Cc: Sunil Goutham <sgoutham@marvell.com>
Cc: linux-arm-kernel@lists.infradead.org
Link: https://lore.kernel.org/bpf/20210624160609.292325-10-toke@redhat.com
This commit is contained in:
Toke Høiland-Jørgensen 2021-06-24 18:05:59 +02:00 committed by Daniel Borkmann
parent 158c1399fc
commit 36baafe347
1 changed files with 0 additions and 2 deletions
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2
drivers/net/ethernet/cavium/thunder/nicvf_main.c
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@ -555,9 +555,7 @@ static inline bool nicvf_xdp_rx(struct nicvf *nic, struct bpf_prog *prog,
xdp_prepare_buff(&xdp, hard_start, data - hard_start, len, false);
orig_data = xdp.data;
rcu_read_lock();
action = bpf_prog_run_xdp(prog, &xdp);
rcu_read_unlock();
len = xdp.data_end - xdp.data;
/* Check if XDP program has changed headers */