From: Andrea Righi <arighi@nvidia.com>
Date: Tue, 1 Jul 2025 06:08:45 +0000 (+0200)
Subject: selftests/sched_ext: Fix exit selftest hang on UP
X-Git-Tag: v6.16-rc7~15^2~2
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=7980ad7e4ca80f6c255f4473fba82a475342035a;p=thirdparty%2Fkernel%2Flinux.git

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 9451782689de1..ee25824b1cbe6 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;