Executing the test_maps binary on platforms with extremely high core counts may cause intermittent assertion failures in test_update_delete() (called via test_map_parallel()). This can occur because bpf_map_update_elem() under some circumstances (specifically in this case while performing bpf_map_update_elem() with BPF_NOEXIST on a BPF_MAP_TYPE_HASH with its map_flags set to BPF_F_NO_PREALLOC) can return an E2BIG error code i.e. error -7 7 tools/testing/selftests/bpf/test_maps.c:#: void test_update_delete(unsigned int, void *): Assertion `err == 0' failed. tools/testing/selftests/bpf/test_maps.c:#: void __run_parallel(unsigned int, void (*)(unsigned int, void *), void *): Assertion `status == 0' failed. As it turns out, is_map_full() which is called from alloc_htab_elem() can take on a conservative approach when htab->use_percpu_counter is true (which is the case here because the percpu_counter is used when a BPF_MAP_TYPE_HASH is created with its map_flags set to BPF_F_NO_PREALLOC). This conservative approach approach prioritizes preventing over-allocation and potential issues that could arise from possibly exceeding htab->map.max_entries in highly concurrent environments, even if it means slightly under-utilizing the htab map's capacity. Given that bpf_map_update_elem() from test_update_delete() can return E2BIG, update can_retry() such that it also accounts for the E2BIG error code (specifically only when running with map_flags being set to BPF_F_NO_PREALLOC). The retry loop will allow the global count belonging to the percpu_counter to become synchronized and better reflect the current htab map's capacity. Signed-off-by: Matt Bobrowski --- tools/testing/selftests/bpf/test_maps.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/bpf/test_maps.c b/tools/testing/selftests/bpf/test_maps.c index 3fae9ce46ca9..ccc5acd55ff9 100644 --- a/tools/testing/selftests/bpf/test_maps.c +++ b/tools/testing/selftests/bpf/test_maps.c @@ -1399,7 +1399,8 @@ static void test_map_stress(void) static bool can_retry(int err) { return (err == EAGAIN || err == EBUSY || - (err == ENOMEM && map_opts.map_flags == BPF_F_NO_PREALLOC)); + ((err == ENOMEM || err == E2BIG) && + map_opts.map_flags == BPF_F_NO_PREALLOC)); } int map_update_retriable(int map_fd, const void *key, const void *value, int flags, int attempts, -- 2.51.2.1041.gc1ab5b90ca-goog