[PATCH bpf-next v6 2/2] selftests/bpf: Remove flaky test_btf_id test

[Yonghong Song <yonghong.song@linux.dev>]

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>
---
 tools/testing/selftests/bpf/prog_tests/btf.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/btf.c b/tools/testing/selftests/bpf/prog_tests/btf.c
index 8fb4a04fbbc0..816145bcb647 100644
--- 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_num)
 	/* 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");
 
-- 
2.34.1