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selftests/bpf: Fix map_kptr test failure

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On my arm64 machine, I get the following failure:
  ...
  tester_init:PASS:tester_log_buf 0 nsec
  process_subtest:PASS:obj_open_mem 0 nsec
  process_subtest:PASS:specs_alloc 0 nsec
  serial_test_map_kptr:PASS:rcu_tasks_trace_gp__open_and_load 0 nsec
  ...
  test_map_kptr_success:PASS:map_kptr__open_and_load 0 nsec
  test_map_kptr_success:PASS:test_map_kptr_ref1 refcount 0 nsec
  test_map_kptr_success:FAIL:test_map_kptr_ref1 retval unexpected error: 2 (errno 2)
  test_map_kptr_success:PASS:test_map_kptr_ref2 refcount 0 nsec
  test_map_kptr_success:FAIL:test_map_kptr_ref2 retval unexpected error: 1 (errno 2)
  ...
  #201/21  map_kptr/success-map:FAIL

In serial_test_map_kptr(), before test_map_kptr_success(), one
kern_sync_rcu() is used to have some delay for freeing the map.
But in my environment, one kern_sync_rcu() seems not enough and
caused the test failure.

In bpf_map_free_in_work() in syscall.c, the queue time for
  queue_work(system_dfl_wq, &map->work)
may be longer than expected. This may cause the test failure
since test_map_kptr_success() expects all previous maps having been freed.

Since it is not clear how long queue_work() time takes, a bpf prog
is added to count the reference after bpf_kfunc_call_test_acquire().
If the number of references is 2 (for initial ref and the one just
acquired), all previous maps should have been released. This will
resolve the above 'retval unexpected error' issue.

Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/bpf/20260116052245.3692405-1-yonghong.song@linux.dev
This commit is contained in:
Yonghong Song 2026-01-15 21:22:45 -08:00 committed by Andrii Nakryiko
parent 47d440d0a5
commit efad162f5a
2 changed files with 41 additions and 0 deletions
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23
tools/testing/selftests/bpf/prog_tests/map_kptr.c
View File

@ -131,6 +131,25 @@ static int kern_sync_rcu_tasks_trace(struct rcu_tasks_trace_gp *rcu)
return 0;
}
static void wait_for_map_release(void)
{
LIBBPF_OPTS(bpf_test_run_opts, lopts);
struct map_kptr *skel;
int ret;
skel = map_kptr__open_and_load();
if (!ASSERT_OK_PTR(skel, "map_kptr__open_and_load"))
return;
do {
ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.count_ref), &lopts);
ASSERT_OK(ret, "count_ref ret");
ASSERT_OK(lopts.retval, "count_ref retval");
} while (skel->bss->num_of_refs != 2);
map_kptr__destroy(skel);
}
void serial_test_map_kptr(void)
{
struct rcu_tasks_trace_gp *skel;
@ -148,11 +167,15 @@ void serial_test_map_kptr(void)
ASSERT_OK(kern_sync_rcu_tasks_trace(skel), "sync rcu_tasks_trace");
ASSERT_OK(kern_sync_rcu(), "sync rcu");
wait_for_map_release();
/* Observe refcount dropping to 1 on bpf_map_free_deferred */
test_map_kptr_success(false);
ASSERT_OK(kern_sync_rcu_tasks_trace(skel), "sync rcu_tasks_trace");
ASSERT_OK(kern_sync_rcu(), "sync rcu");
wait_for_map_release();
/* Observe refcount dropping to 1 on synchronous delete elem */
test_map_kptr_success(true);
}

18
tools/testing/selftests/bpf/progs/map_kptr.c
View File

@ -487,6 +487,24 @@ int test_map_kptr_ref3(struct __sk_buff *ctx)
return 0;
}
int num_of_refs;
SEC("syscall")
int count_ref(void *ctx)
{
struct prog_test_ref_kfunc *p;
unsigned long arg = 0;
p = bpf_kfunc_call_test_acquire(&arg);
if (!p)
return 1;
num_of_refs = p->cnt.refs.counter;
bpf_kfunc_call_test_release(p);
return 0;
}
SEC("syscall")
int test_ls_map_kptr_ref1(void *ctx)
{