[PATCH] kunit: tool: skip stty when stdin is not a tty

[Shuvam Pandey <shuvampandey1@gmail.com>]

run_kernel() cleanup and signal_handler() invoke stty unconditionally.
When stdin is not a tty (for example in CI or unit tests), this writes
noise to stderr.

Call stty only when stdin is a tty.

Add regression tests for these paths:
- run_kernel() with non-tty stdin
- signal_handler() with non-tty stdin
- signal_handler() with tty stdin

Signed-off-by: Shuvam Pandey <shuvampandey1@gmail.com>
---
 tools/testing/kunit/kunit_kernel.py    | 10 ++++--
 tools/testing/kunit/kunit_tool_test.py | 42 ++++++++++++++++++++++++++
 2 files changed, 50 insertions(+), 2 deletions(-)

diff --git a/tools/testing/kunit/kunit_kernel.py b/tools/testing/kunit/kunit_kernel.py
index 260d8d9aa1db..6f49b184a6fb 100644
--- a/tools/testing/kunit/kunit_kernel.py
+++ b/tools/testing/kunit/kunit_kernel.py
@@ -345,6 +345,12 @@ class LinuxSourceTree:
 			return False
 		return self.validate_config(build_dir)
 
+	def _restore_terminal_if_tty(self) -> None:
+		# stty requires a controlling terminal; skip headless runs.
+		if sys.stdin is None or not sys.stdin.isatty():
+			return
+		subprocess.call(['stty', 'sane'])
+
 	def run_kernel(self, args: Optional[List[str]]=None, build_dir: str='', filter_glob: str='', filter: str='', filter_action: Optional[str]=None, timeout: Optional[int]=None) -> Iterator[str]:
 		if not args:
 			args = []
@@ -384,8 +390,8 @@ class LinuxSourceTree:
 			process.stdout.close()
 
 			waiter.join()
-			subprocess.call(['stty', 'sane'])
+			self._restore_terminal_if_tty()
 
 	def signal_handler(self, unused_sig: int, unused_frame: Optional[FrameType]) -> None:
 		logging.error('Build interruption occurred. Cleaning console.')
-		subprocess.call(['stty', 'sane'])
+		self._restore_terminal_if_tty()
diff --git a/tools/testing/kunit/kunit_tool_test.py b/tools/testing/kunit/kunit_tool_test.py
index b67408147c1f..201d5245a9f4 100755
--- a/tools/testing/kunit/kunit_tool_test.py
+++ b/tools/testing/kunit/kunit_tool_test.py
@@ -503,6 +503,48 @@ class LinuxSourceTreeTest(unittest.TestCase):
 			with open(kunit_kernel.get_outfile_path(build_dir), 'rt') as outfile:
 				self.assertEqual(outfile.read(), 'hi\nbye\n', msg='Missing some output')
 
+	def test_run_kernel_skips_terminal_reset_without_tty(self):
+		def fake_start(unused_args, unused_build_dir):
+			return subprocess.Popen(['printf', 'KTAP version 1\n'],
+						text=True, stdout=subprocess.PIPE)
+
+		non_tty_stdin = mock.Mock()
+		non_tty_stdin.isatty.return_value = False
+
+		with tempfile.TemporaryDirectory('') as build_dir:
+			tree = kunit_kernel.LinuxSourceTree(build_dir, kunitconfig_paths=[os.devnull])
+			with mock.patch.object(tree._ops, 'start', side_effect=fake_start), \
+			     mock.patch.object(kunit_kernel.sys, 'stdin', non_tty_stdin), \
+			     mock.patch.object(kunit_kernel.subprocess, 'call') as mock_call:
+				for _ in tree.run_kernel(build_dir=build_dir):
+					pass
+
+				mock_call.assert_not_called()
+
+	def test_signal_handler_skips_terminal_reset_without_tty(self):
+		non_tty_stdin = mock.Mock()
+		non_tty_stdin.isatty.return_value = False
+		tree = kunit_kernel.LinuxSourceTree('', kunitconfig_paths=[os.devnull])
+
+		with mock.patch.object(kunit_kernel.sys, 'stdin', non_tty_stdin), \
+		     mock.patch.object(kunit_kernel.subprocess, 'call') as mock_call, \
+		     mock.patch.object(kunit_kernel.logging, 'error') as mock_error:
+			tree.signal_handler(signal.SIGINT, None)
+			mock_error.assert_called_once()
+			mock_call.assert_not_called()
+
+	def test_signal_handler_resets_terminal_with_tty(self):
+		tty_stdin = mock.Mock()
+		tty_stdin.isatty.return_value = True
+		tree = kunit_kernel.LinuxSourceTree('', kunitconfig_paths=[os.devnull])
+
+		with mock.patch.object(kunit_kernel.sys, 'stdin', tty_stdin), \
+		     mock.patch.object(kunit_kernel.subprocess, 'call') as mock_call, \
+		     mock.patch.object(kunit_kernel.logging, 'error') as mock_error:
+			tree.signal_handler(signal.SIGINT, None)
+			mock_error.assert_called_once()
+			mock_call.assert_called_once_with(['stty', 'sane'])
+
 	def test_build_reconfig_no_config(self):
 		with tempfile.TemporaryDirectory('') as build_dir:
 			with open(kunit_kernel.get_kunitconfig_path(build_dir), 'w') as f:

base-commit: a75cb869a8ccc88b0bc7a44e1597d9c7995c56e5
-- 
2.50.0