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bpf: Remove redundant synchronize_rcu.

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bpf_free_used_maps() or close(map_fd) will trigger map_free callback.
bpf_free_used_maps() is called after bpf prog is no longer executing:
bpf_prog_put->call_rcu->bpf_prog_free->bpf_free_used_maps.
Hence there is no need to call synchronize_rcu() to protect map elements.

Note that hash_of_maps and array_of_maps update/delete inner maps via
sys_bpf() that calls maybe_wait_bpf_programs() and synchronize_rcu().

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Link: https://lore.kernel.org/bpf/20200630043343.53195-2-alexei.starovoitov@gmail.com
This commit is contained in:
Alexei Starovoitov 2020-06-29 21:33:39 -07:00
parent 8c18311067
commit bba1dc0b55
7 changed files with 3 additions and 38 deletions
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2
kernel/bpf/reuseport_array.c
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@ -96,8 +96,6 @@ static void reuseport_array_free(struct bpf_map *map)
struct sock *sk;
u32 i;
synchronize_rcu();
/*
* ops->map_*_elem() will not be able to access this
* array now. Hence, this function only races with