[PATCH 6.6 321/322] selftests/bpf: Remove flaky test_btf_id test

Greg Kroah-Hartman
2024-02-03T04:15:22Z

From: Yonghong Song <yonghong.song@linux.dev>

commit 56925f389e152dcb8d093435d43b78a310539c23 upstream.

With previous patch, one of subtests in test_btf_id becomes
flaky and may fail. The following is a failing example:

Error: #26 btf
Error: #26/174 btf/BTF ID
Error: #26/174 btf/BTF ID
btf_raw_create:PASS:check 0 nsec
btf_raw_create:PASS:check 0 nsec
test_btf_id:PASS:check 0 nsec
...
test_btf_id:PASS:check 0 nsec
test_btf_id:FAIL:check BTF lingersdo_test_get_info:FAIL:check failed: -1

The test tries to prove a btf_id not available after the map is closed.
But btf_id is freed only after workqueue and a rcu grace period, compared
to previous case just after a rcu grade period.
Depending on system workload, workqueue could take quite some time
to execute function bpf_map_free_deferred() which may cause the test failure.
Instead of adding arbitrary delays, let us remove the logic to
check btf_id availability after map is closed.

Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20231214203820.1469402-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Samasth Norway Ananda <samasth.norway.ananda@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
tools/testing/selftests/bpf/prog_tests/btf.c | 5 -----
1 file changed, 5 deletions(-)

--- a/tools/testing/selftests/bpf/prog_tests/btf.c
+++ b/tools/testing/selftests/bpf/prog_tests/btf.c
@@ -4630,11 +4630,6 @@ static int test_btf_id(unsigned int test
/* The map holds the last ref to BTF and its btf_id */
close(map_fd);
map_fd = -1;
- btf_fd[0] = bpf_btf_get_fd_by_id(map_info.btf_id);
- if (CHECK(btf_fd[0] >= 0, "BTF lingers")) {
- err = -1;
- goto done;
- }

fprintf(stderr, "OK");