test: bound CPU vocoder reference threads (#8347)

Signed-off-by: andyluo7 <andy.luo@amd.com>

tests/model_executor/models/cosyvoice3/test_cosyvoice3_f0_weight_norm.py

@@ -10,6 +10,7 @@ from torch.nn.utils import parametrize
 from vllm_omni.model_executor.models.cosyvoice3.code2wav_core import hifigan
 
 pytestmark = [
+    pytest.mark.usefixtures("single_threaded_cpu"),
     pytest.mark.core_model,
     pytest.mark.filterwarnings("ignore:.*weight_norm.*:FutureWarning"),
 ]

tests/model_executor/models/cosyvoice3/test_cosyvoice3_hift_weight_norm.py

@@ -10,6 +10,7 @@ from torch.nn.utils import parametrize
 from vllm_omni.model_executor.models.cosyvoice3.code2wav_core import hifigan
 
 pytestmark = [
+    pytest.mark.usefixtures("single_threaded_cpu"),
     pytest.mark.core_model,
     pytest.mark.cpu,
     # The legacy weight_norm API warns on construction; the "legacy" params

tests/model_executor/models/cosyvoice3/test_cosyvoice3_incremental_hift.py

@@ -31,9 +31,8 @@ from vllm_omni.model_executor.models.cosyvoice3.code2wav_core.hifigan import (
     _wrapped_slice,
 )
 from vllm_omni.model_executor.models.cosyvoice3.cosyvoice3_code2wav import CosyVoice3Code2Wav
-from vllm_omni.platforms import current_omni_platform
 
-pytestmark = [pytest.mark.core_model, pytest.mark.cpu]
+pytestmark = [pytest.mark.core_model, pytest.mark.cpu, pytest.mark.usefixtures("single_threaded_cpu")]
 
 CHUNK_LEN = 24
 TOTAL_MEL = 96
@@ -341,10 +340,6 @@ def test_incremental_hift_matches_reference_for_voiced_f0(config):
 
 @pytest.mark.parametrize("config", CONFIGS)
 @pytest.mark.parametrize("first_len,step_len", [(10, 6), (10, 3), (20, 3), (10, 1)])
-@pytest.mark.skipif(
-    current_omni_platform.is_rocm(),
-    reason="exhaustive CPU reference matrix exceeds the AMD CI time budget",
-)
 def test_incremental_hift_matches_reference_for_voiced_f0_small_chunks(config, first_len, step_len):
     """Same as test_incremental_hift_matches_reference_for_voiced_f0, but with small,
     sub-receptive-field chunk sizes (down to 1 mel frame) instead of the uniform