Occasionally, with './test_progs -j' on my vm, I will hit the
following failure:
test_cgrp_local_storage:PASS:join_cgroup /cgrp_local_storage 0 nsec
test_cgroup_iter_sleepable:PASS:skel_open 0 nsec
test_cgroup_iter_sleepable:PASS:skel_load 0 nsec
test_cgroup_iter_sleepable:PASS:attach_iter 0 nsec
test_cgroup_iter_sleepable:PASS:iter_create 0 nsec
test_cgroup_iter_sleepable:FAIL:cgroup_id unexpected cgroup_id: actual 1 != expected 2812
#48/5 cgrp_local_storage/cgroup_iter_sleepable:FAIL
#48 cgrp_local_storage:FAIL
Finally, I decided to do some investigation since the test is introduced
by myself. It turns out the reason is due to cgroup_fd with value 0.
In cgroup_iter, a cgroup_fd of value 0 means the root cgroup.
/* from cgroup_iter.c */
if (fd)
cgrp = cgroup_v1v2_get_from_fd(fd);
else if (id)
cgrp = cgroup_get_from_id(id);
else /* walk the entire hierarchy by default. */
cgrp = cgroup_get_from_path("/");
That is why we got cgroup_id 1 instead of expected 2812.
Why we got a cgroup_fd 0? Nobody should really touch 'stdin' (fd 0) in test_progs.
I traced 'close' syscall with stack trace and found the root cause,
which is a bug in bpf_obj_pinning.c. Basically, the code closed fd 0
although it should not. Fixing the bug in bpf_obj_pinning.c
also resolved the above cgroup_iter_sleepable subtest failure.
Fixes: 3b22f98e5a05 ("selftests/bpf: Add path_fd-based BPF_OBJ_PIN and BPF_OBJ_GET tests")
Signed-off-by: Yonghong Song <yonghong.song@xxxxxxxxx>
---
tools/testing/selftests/bpf/prog_tests/bpf_obj_pinning.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_obj_pinning.c b/tools/testing/selftests/bpf/prog_tests/bpf_obj_pinning.c
index 31f1e815f671..ee0458a5ce78 100644
--- a/tools/testing/selftests/bpf/prog_tests/bpf_obj_pinning.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_obj_pinning.c
@@ -8,6 +8,7 @@
#include <linux/unistd.h>
#include <linux/mount.h>
#include <sys/syscall.h>
+#include "bpf/libbpf_internal.h"
static inline int sys_fsopen(const char *fsname, unsigned flags)
{
@@ -155,7 +156,7 @@ static void validate_pin(int map_fd, const char *map_name, int src_value,
ASSERT_OK(err, "obj_pin");
/* cleanup */
- if (pin_opts.path_fd >= 0)
+ if (path_kind == PATH_FD_REL && pin_opts.path_fd >= 0)
close(pin_opts.path_fd);
if (old_cwd[0])
ASSERT_OK(chdir(old_cwd), "restore_cwd");
@@ -220,7 +221,7 @@ static void validate_get(int map_fd, const char *map_name, int src_value,
goto cleanup;
/* cleanup */
- if (get_opts.path_fd >= 0)
+ if (path_kind == PATH_FD_REL && get_opts.path_fd >= 0)
close(get_opts.path_fd);
if (old_cwd[0])
ASSERT_OK(chdir(old_cwd), "restore_cwd");
--
2.34.1
