From 49c64ffb2fd996af4c82007196c61e17d74cb1ab Mon Sep 17 00:00:00 2001 From: Tianyi Chen Date: Sun, 6 Sep 2026 21:55:22 +0800 Subject: selftests/sched_ext: Handle CPU hotplug write failures toggle_online_status() logs failed CPU state changes but discards the write result. The hotplug tests can consequently wait indefinitely for a scheduler exit that the failed operation never triggered. Return the write result and stop both hotplug tests when a required CPU state change fails. Release the acquired scheduler resources on these paths and let the existing cleanup callback retry restoring CPU1. Also fail the test when its normal CPU restoration fails. Tested in a two-vCPU VM running a kernel built from the same source as the selftests. Injecting EIO with strace into each of the ten CPU state writes makes the fixed test return 1, with CPU1 online and sched_ext disabled after cleanup. The original test does not finish within three seconds when either of the first two writes fails. Normal hotplug tests pass before and after the change. Making the online file read-only also produces a failure without hanging. Fixes: a5db7817af78 ("sched_ext: Add selftests") Assisted-by: LLM Signed-off-by: Tianyi Chen Signed-off-by: Tejun Heo --- tools/testing/selftests/sched_ext/hotplug.c | 34 +++++++++++++++++++---------- 1 file changed, 23 insertions(+), 11 deletions(-) diff --git a/tools/testing/selftests/sched_ext/hotplug.c b/tools/testing/selftests/sched_ext/hotplug.c index 0cfbb111a2d0..10b8d42bd89b 100644 --- a/tools/testing/selftests/sched_ext/hotplug.c +++ b/tools/testing/selftests/sched_ext/hotplug.c @@ -21,15 +21,17 @@ static bool is_cpu_online(void) return file_read_long(online_path) > 0; } -static void toggle_online_status(bool online) +static int toggle_online_status(bool online) { long val = online ? 1 : 0; int ret; ret = file_write_long(online_path, val); if (ret != 0) - fprintf(stderr, "Failed to bring CPU %s (%s)", + fprintf(stderr, "Failed to bring CPU %s (%s)\n", online ? "online" : "offline", strerror(errno)); + + return ret; } static enum scx_test_status setup(void **ctx) @@ -44,6 +46,7 @@ static enum scx_test_status test_hotplug(bool onlining, bool cbs_defined) { struct hotplug *skel; struct bpf_link *link; + enum scx_test_status status = SCX_TEST_FAIL; long kind, code; SCX_ASSERT(is_cpu_online()); @@ -54,8 +57,8 @@ static enum scx_test_status test_hotplug(bool onlining, bool cbs_defined) SCX_FAIL_IF(hotplug__load(skel), "Failed to load skel"); /* Testing the offline -> online path, so go offline before starting */ - if (onlining) - toggle_online_status(0); + if (onlining && toggle_online_status(0)) + goto out_destroy_skel; if (cbs_defined) { kind = SCX_KIND_VAL(SCX_EXIT_UNREG_BPF); @@ -79,7 +82,8 @@ static enum scx_test_status test_hotplug(bool onlining, bool cbs_defined) return SCX_TEST_FAIL; } - toggle_online_status(onlining ? 1 : 0); + if (toggle_online_status(onlining ? 1 : 0)) + goto out_destroy_link; while (!UEI_EXITED(skel, uei)) sched_yield(); @@ -87,20 +91,23 @@ static enum scx_test_status test_hotplug(bool onlining, bool cbs_defined) SCX_EQ(skel->data->uei.kind, kind); SCX_EQ(UEI_REPORT(skel, uei), code); - if (!onlining) - toggle_online_status(1); + if (!onlining && toggle_online_status(1)) + goto out_destroy_link; + status = SCX_TEST_PASS; +out_destroy_link: bpf_link__destroy(link); +out_destroy_skel: hotplug__destroy(skel); - return SCX_TEST_PASS; + return status; } static enum scx_test_status test_hotplug_attach(void) { struct hotplug *skel; struct bpf_link *link; - enum scx_test_status status = SCX_TEST_PASS; + enum scx_test_status status = SCX_TEST_FAIL; long kind, code; SCX_ASSERT(is_cpu_online()); @@ -115,10 +122,12 @@ static enum scx_test_status test_hotplug_attach(void) * Take the CPU offline to increment the global hotplug seq, which * should cause attach to fail due to us setting the hotplug seq above */ - toggle_online_status(0); + if (toggle_online_status(0)) + goto out_destroy_skel; link = bpf_map__attach_struct_ops(skel->maps.hotplug_nocb_ops); - toggle_online_status(1); + if (toggle_online_status(1)) + goto out_destroy_link; SCX_ASSERT(link); while (!UEI_EXITED(skel, uei)) @@ -130,7 +139,10 @@ static enum scx_test_status test_hotplug_attach(void) SCX_EQ(skel->data->uei.kind, kind); SCX_EQ(UEI_REPORT(skel, uei), code); + status = SCX_TEST_PASS; +out_destroy_link: bpf_link__destroy(link); +out_destroy_skel: hotplug__destroy(skel); return status; -- cgit v1.2.3