linux-kernel - [PATCH sched_ext/for-6.13-fixes] sched_ext: Fix dsq_local

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Message-ID: <Z2tNK2oFDX1OPp8C@slm.duckdns.org>
Date: Tue, 24 Dec 2024 14:09:15 -1000
From: Tejun Heo <tj@...nel.org>
To: Ihor Solodrai <ihor.solodrai@...me>
Cc: David Vernet <void@...ifault.com>, sched-ext@...a.com,
	kernel-team@...a.com, linux-kernel@...r.kernel.org,
	bpf <bpf@...r.kernel.org>
Subject: [PATCH sched_ext/for-6.13-fixes] sched_ext: Fix dsq_local_on selftest

The dsp_local_on selftest expects the scheduler to fail by trying to
schedule an e.g. CPU-affine task to the wrong CPU. However, this isn't
guaranteed to happen in the 1 second window that the test is running.
Besides, it's odd to have this particular exception path tested when there
are no other tests that verify that the interface is working at all - e.g.
the test would pass if dsp_local_on interface is completely broken and fails
on any attempt.

Flip the test so that it verifies that the feature works. While at it, fix a
typo in the info message.

Signed-off-by: Tejun Heo <tj@...nel.org>
Reported-by: Ihor Solodrai <ihor.solodrai@...me>
Link: http://lkml.kernel.org/r/Z1n9v7Z6iNJ-wKmq@slm.duckdns.org
---
 tools/testing/selftests/sched_ext/dsp_local_on.bpf.c |    5 ++++-
 tools/testing/selftests/sched_ext/dsp_local_on.c     |    5 +++--
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/sched_ext/dsp_local_on.bpf.c b/tools/testing/selftests/sched_ext/dsp_local_on.bpf.c
index 6325bf76f47e..fbda6bf54671 100644
--- a/tools/testing/selftests/sched_ext/dsp_local_on.bpf.c
+++ b/tools/testing/selftests/sched_ext/dsp_local_on.bpf.c
@@ -43,7 +43,10 @@ void BPF_STRUCT_OPS(dsp_local_on_dispatch, s32 cpu, struct task_struct *prev)
 	if (!p)
 		return;
 
-	target = bpf_get_prandom_u32() % nr_cpus;
+	if (p->nr_cpus_allowed == nr_cpus)
+		target = bpf_get_prandom_u32() % nr_cpus;
+	else
+		target = scx_bpf_task_cpu(p);
 
 	scx_bpf_dsq_insert(p, SCX_DSQ_LOCAL_ON | target, SCX_SLICE_DFL, 0);
 	bpf_task_release(p);
diff --git a/tools/testing/selftests/sched_ext/dsp_local_on.c b/tools/testing/selftests/sched_ext/dsp_local_on.c
index 472851b56854..0ff27e57fe43 100644
--- a/tools/testing/selftests/sched_ext/dsp_local_on.c
+++ b/tools/testing/selftests/sched_ext/dsp_local_on.c
@@ -34,9 +34,10 @@ static enum scx_test_status run(void *ctx)
 	/* Just sleeping is fine, plenty of scheduling events happening */
 	sleep(1);
 
-	SCX_EQ(skel->data->uei.kind, EXIT_KIND(SCX_EXIT_ERROR));
 	bpf_link__destroy(link);
 
+	SCX_EQ(skel->data->uei.kind, EXIT_KIND(SCX_EXIT_UNREG));
+
 	return SCX_TEST_PASS;
 }
 
@@ -50,7 +51,7 @@ static void cleanup(void *ctx)
 struct scx_test dsp_local_on = {
 	.name = "dsp_local_on",
 	.description = "Verify we can directly dispatch tasks to a local DSQs "
-		       "from osp.dispatch()",
+		       "from ops.dispatch()",
 	.setup = setup,
 	.run = run,
 	.cleanup = cleanup,