selftests/sched_ext: Fix exit selftest hang on UP
On single-CPU systems, ops.select_cpu() is never called, causing the
EXIT_SELECT_CPU test case to wait indefinitely.
Avoid the stall by skipping this specific sub-test when only one CPU is
available.
Reported-by: Phil Auld <pauld@redhat.com>
Fixes: a5db7817af780 ("sched_ext: Add selftests")
Signed-off-by: Andrea Righi <arighi@nvidia.com>
Reviewed-by: Phil Auld <pauld@redhat.com>
Tested-by: Phil Auld <pauld@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
diff --git a/tools/testing/selftests/sched_ext/exit.c b/tools/testing/selftests/sched_ext/exit.c
index 9451782..ee25824 100644
--- a/tools/testing/selftests/sched_ext/exit.c
+++ b/tools/testing/selftests/sched_ext/exit.c
@@ -22,6 +22,14 @@ static enum scx_test_status run(void *ctx)
struct bpf_link *link;
char buf[16];
+ /*
+ * On single-CPU systems, ops.select_cpu() is never
+ * invoked, so skip this test to avoid getting stuck
+ * indefinitely.
+ */
+ if (tc == EXIT_SELECT_CPU && libbpf_num_possible_cpus() == 1)
+ continue;
+
skel = exit__open();
SCX_ENUM_INIT(skel);
skel->rodata->exit_point = tc;
