From: Yonghong Song yonghong.song@linux.dev

[ Upstream commit 56925f389e152dcb8d093435d43b78a310539c23 ]

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 [Samasth: backport for 6.6.y] Signed-off-by: Samasth Norway Ananda samasth.norway.ananda@oracle.com --- Above patch is a fix for 59e5791f59dd ("bpf: Fix a race condition between btf_put() and map_free()"). While the commit causing the error is present in 6.6.y the fix is not present. --- 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 92d51f377fe5..0c0881c7eb1a 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");