On Mon, Jul 26, 2021 at 8:19 AM Martynas Pumputis <m@xxxxxxxxx> wrote:
>
> When loading in parallel multiple programs which use the same to-be
> pinned map, it is possible that two instances of the loader will call
> bpf_object__create_maps() at the same time. If the map doesn't exist
> when both instances call bpf_object__reuse_map(), then one of the
> instances will fail with EEXIST when calling bpf_map__pin().
>
> Fix the race by retrying reusing a map if bpf_map__pin() returns
> EEXIST. The fix is similar to the one in iproute2: e4c4685fd6e4 ("bpf:
> Fix race condition with map pinning").
>
> Before retrying the pinning, we don't do any special cleaning of an
> internal map state. The closer code inspection revealed that it's not
> required:
>
> - bpf_object__create_map(): map->inner_map is destroyed after a
> successful call, map->fd is closed if pinning fails.
> - bpf_object__populate_internal_map(): created map elements is
> destroyed upon close(map->fd).
> - init_map_slots(): slots are freed after their initialization.
>
> Cc: Joe Stringer <joe@xxxxxxxxxxx>
> Signed-off-by: Martynas Pumputis <m@xxxxxxxxx>
> ---
Applied to bpf-next, thanks.
> tools/lib/bpf/libbpf.c | 15 ++++++++++++++-
> 1 file changed, 14 insertions(+), 1 deletion(-)
>
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