[Python-checkins] cpython (merge 3.4 -> default): (Merge 3.4) Python issue #21645, Tulip issue 192: Rewrite signal handling
victor.stinner
python-checkins at python.org
Thu Jul 17 22:49:26 CEST 2014
http://hg.python.org/cpython/rev/2176496951a4
changeset: 91720:2176496951a4
parent: 91718:84f9bf424720
parent: 91719:c4f053f1b47f
user: Victor Stinner <victor.stinner at gmail.com>
date: Thu Jul 17 22:45:42 2014 +0200
summary:
(Merge 3.4) Python issue #21645, Tulip issue 192: Rewrite signal handling
Since Python 3.3, the C signal handler writes the signal number into the wakeup
file descriptor and then schedules the Python call using Py_AddPendingCall().
asyncio uses the wakeup file descriptor to wake up the event loop, and relies
on Py_AddPendingCall() to schedule the final callback with call_soon().
If the C signal handler is called in a thread different than the thread of the
event loop, the loop is awaken but Py_AddPendingCall() was not called yet. In
this case, the event loop has nothing to do and go to sleep again.
Py_AddPendingCall() is called while the event loop is sleeping again and so the
final callback is not scheduled immediatly.
This patch changes how asyncio handles signals. Instead of relying on
Py_AddPendingCall() and the wakeup file descriptor, asyncio now only relies on
the wakeup file descriptor. asyncio reads signal numbers from the wakeup file
descriptor to call its signal handler.
files:
Lib/asyncio/proactor_events.py | 2 +-
Lib/asyncio/selector_events.py | 6 ++-
Lib/asyncio/unix_events.py | 20 +++++++++-
Lib/test/test_asyncio/test_proactor_events.py | 2 +-
Lib/test/test_asyncio/test_unix_events.py | 4 +-
5 files changed, 27 insertions(+), 7 deletions(-)
diff --git a/Lib/asyncio/proactor_events.py b/Lib/asyncio/proactor_events.py
--- a/Lib/asyncio/proactor_events.py
+++ b/Lib/asyncio/proactor_events.py
@@ -443,7 +443,7 @@
f.add_done_callback(self._loop_self_reading)
def _write_to_self(self):
- self._csock.send(b'x')
+ self._csock.send(b'\0')
def _start_serving(self, protocol_factory, sock, ssl=None, server=None):
if ssl:
diff --git a/Lib/asyncio/selector_events.py b/Lib/asyncio/selector_events.py
--- a/Lib/asyncio/selector_events.py
+++ b/Lib/asyncio/selector_events.py
@@ -94,12 +94,16 @@
self._internal_fds += 1
self.add_reader(self._ssock.fileno(), self._read_from_self)
+ def _process_self_data(self, data):
+ pass
+
def _read_from_self(self):
while True:
try:
data = self._ssock.recv(4096)
if not data:
break
+ self._process_self_data(data)
except InterruptedError:
continue
except BlockingIOError:
@@ -114,7 +118,7 @@
csock = self._csock
if csock is not None:
try:
- csock.send(b'x')
+ csock.send(b'\0')
except OSError:
pass
diff --git a/Lib/asyncio/unix_events.py b/Lib/asyncio/unix_events.py
--- a/Lib/asyncio/unix_events.py
+++ b/Lib/asyncio/unix_events.py
@@ -31,6 +31,11 @@
raise ImportError('Signals are not really supported on Windows')
+def _sighandler_noop(signum, frame):
+ """Dummy signal handler."""
+ pass
+
+
class _UnixSelectorEventLoop(selector_events.BaseSelectorEventLoop):
"""Unix event loop.
@@ -49,6 +54,13 @@
for sig in list(self._signal_handlers):
self.remove_signal_handler(sig)
+ def _process_self_data(self, data):
+ for signum in data:
+ if not signum:
+ # ignore null bytes written by _write_to_self()
+ continue
+ self._handle_signal(signum)
+
def add_signal_handler(self, sig, callback, *args):
"""Add a handler for a signal. UNIX only.
@@ -69,7 +81,11 @@
self._signal_handlers[sig] = handle
try:
- signal.signal(sig, self._handle_signal)
+ # Register a dummy signal handler to ask Python to write the signal
+ # number in the wakup file descriptor. _process_self_data() will
+ # read signal numbers from this file descriptor to handle signals.
+ signal.signal(sig, _sighandler_noop)
+
# Set SA_RESTART to limit EINTR occurrences.
signal.siginterrupt(sig, False)
except OSError as exc:
@@ -85,7 +101,7 @@
else:
raise
- def _handle_signal(self, sig, arg):
+ def _handle_signal(self, sig):
"""Internal helper that is the actual signal handler."""
handle = self._signal_handlers.get(sig)
if handle is None:
diff --git a/Lib/test/test_asyncio/test_proactor_events.py b/Lib/test/test_asyncio/test_proactor_events.py
--- a/Lib/test/test_asyncio/test_proactor_events.py
+++ b/Lib/test/test_asyncio/test_proactor_events.py
@@ -435,7 +435,7 @@
def test_write_to_self(self):
self.loop._write_to_self()
- self.csock.send.assert_called_with(b'x')
+ self.csock.send.assert_called_with(b'\0')
def test_process_events(self):
self.loop._process_events([])
diff --git a/Lib/test/test_asyncio/test_unix_events.py b/Lib/test/test_asyncio/test_unix_events.py
--- a/Lib/test/test_asyncio/test_unix_events.py
+++ b/Lib/test/test_asyncio/test_unix_events.py
@@ -42,7 +42,7 @@
ValueError, self.loop._check_signal, signal.NSIG + 1)
def test_handle_signal_no_handler(self):
- self.loop._handle_signal(signal.NSIG + 1, ())
+ self.loop._handle_signal(signal.NSIG + 1)
def test_handle_signal_cancelled_handler(self):
h = asyncio.Handle(mock.Mock(), (),
@@ -50,7 +50,7 @@
h.cancel()
self.loop._signal_handlers[signal.NSIG + 1] = h
self.loop.remove_signal_handler = mock.Mock()
- self.loop._handle_signal(signal.NSIG + 1, ())
+ self.loop._handle_signal(signal.NSIG + 1)
self.loop.remove_signal_handler.assert_called_with(signal.NSIG + 1)
@mock.patch('asyncio.unix_events.signal')
--
Repository URL: http://hg.python.org/cpython
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