st_ops_assoc_in_timer_no_uref runs .test_1, which starts a timer to
call it again 500ms later, drops every reference to the struct_ops map,
and expects the timer callback to find no struct_ops associated with
its program anymore.
The association goes away only when the last reference to the map is
dropped. syscall_prog holds one through its own association and drops
it only when it is freed, in a work item after an RCU tasks trace grace
period. With other tests running in parallel, that can take longer than
500ms, and the callback still reaches the struct_ops and gets MAP_MAGIC
instead of -1.
Have the timer callback restart the timer until the map is gone, as it
does for st_ops_assoc_in_timer_free. Calling the struct_ops through the
association until then is safe, as the map is freed only after a grace
period that follows clearing the association.
st_ops_assoc_in_timer_no_uref run 100 times with test_progs -j32 running
in the background, on a KASAN kernel with the fix, x86_64 VM with 32
vCPUs, before and after this patch:
before after
outcome 1 of 100 failed (MAP_MAGIC) 0 of 100 failed (MAP_MAGIC)
Fixes: 0e841d19263a ("selftests/bpf: Test getting associated struct_ops in
timer callback")
Signed-off-by: Qiliang Yuan <[email protected]>
---
tools/testing/selftests/bpf/prog_tests/test_struct_ops_assoc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/testing/selftests/bpf/prog_tests/test_struct_ops_assoc.c
b/tools/testing/selftests/bpf/prog_tests/test_struct_ops_assoc.c
index 9d56e8cb5675a..435653cb7c908 100644
--- a/tools/testing/selftests/bpf/prog_tests/test_struct_ops_assoc.c
+++ b/tools/testing/selftests/bpf/prog_tests/test_struct_ops_assoc.c
@@ -187,7 +187,7 @@ static void run_st_ops_assoc_in_timer_no_uref(int timer_ns,
int wait_map_free,
static void test_st_ops_assoc_in_timer_no_uref(void)
{
- run_st_ops_assoc_in_timer_no_uref(500000000, 0, 0);
+ run_st_ops_assoc_in_timer_no_uref(500000000, 1, 0);
}
/*
--
2.43.0
