Issue #8407: The signal handler writes the signal number as a single byte
instead of a nul byte into the wakeup file descriptor. So it is possible to
wait more than one signal and know which signals were raised.
diff --git a/Doc/library/signal.rst b/Doc/library/signal.rst
index 473eda2..68a5d2c 100644
--- a/Doc/library/signal.rst
+++ b/Doc/library/signal.rst
@@ -262,13 +262,17 @@
.. function:: set_wakeup_fd(fd)
- Set the wakeup fd to *fd*. When a signal is received, a ``'\0'`` byte is
- written to the fd. This can be used by a library to wakeup a poll or select
- call, allowing the signal to be fully processed.
+ Set the wakeup file descriptor to *fd*. When a signal is received, the
+ signal number is written as a single byte into the fd. This can be used by
+ a library to wakeup a poll or select call, allowing the signal to be fully
+ processed.
The old wakeup fd is returned. *fd* must be non-blocking. It is up to the
library to remove any bytes before calling poll or select again.
+ Use for example ``struct.unpack('%uB' % len(data), data)`` to decode the
+ signal numbers list.
+
When threads are enabled, this function can only be called from the main thread;
attempting to call it from other threads will cause a :exc:`ValueError`
exception to be raised.
diff --git a/Doc/whatsnew/3.3.rst b/Doc/whatsnew/3.3.rst
index 14f06af..37f96ce 100644
--- a/Doc/whatsnew/3.3.rst
+++ b/Doc/whatsnew/3.3.rst
@@ -131,6 +131,10 @@
* :func:`~signal.sigpending`: examine pending functions ;
* :func:`~signal.sigwait`: wait a signal.
+* The signal handler writes the signal number as a single byte instead of
+ a nul byte into the wakeup file descriptor. So it is possible to wait more
+ than one signal and know which signals were raised.
+
Optimizations
=============
diff --git a/Lib/test/test_signal.py b/Lib/test/test_signal.py
index c1054ed..80b9744 100644
--- a/Lib/test/test_signal.py
+++ b/Lib/test/test_signal.py
@@ -5,6 +5,7 @@
import pickle
import select
import signal
+import struct
import subprocess
import traceback
import sys, os, time, errno
@@ -236,6 +237,11 @@
TIMEOUT_FULL = 10
TIMEOUT_HALF = 5
+ def check_signum(self, *signals):
+ data = os.read(self.read, len(signals)+1)
+ raised = struct.unpack('%uB' % len(data), data)
+ self.assertSequenceEqual(raised, signals)
+
def test_wakeup_fd_early(self):
import select
@@ -249,6 +255,7 @@
select.select([self.read], [], [], self.TIMEOUT_FULL)
after_time = time.time()
self.assertTrue(after_time - mid_time < self.TIMEOUT_HALF)
+ self.check_signum(signal.SIGALRM)
def test_wakeup_fd_during(self):
import select
@@ -260,6 +267,14 @@
[self.read], [], [], self.TIMEOUT_FULL)
after_time = time.time()
self.assertTrue(after_time - before_time < self.TIMEOUT_HALF)
+ self.check_signum(signal.SIGALRM)
+
+ def test_signum(self):
+ old_handler = signal.signal(signal.SIGUSR1, lambda x,y:None)
+ self.addCleanup(signal.signal, signal.SIGUSR1, old_handler)
+ os.kill(os.getpid(), signal.SIGUSR1)
+ os.kill(os.getpid(), signal.SIGALRM)
+ self.check_signum(signal.SIGUSR1, signal.SIGALRM)
def setUp(self):
import fcntl
diff --git a/Misc/NEWS b/Misc/NEWS
index 274931c..ef78ab7 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -140,6 +140,10 @@
Library
-------
+- Issue #8407: The signal handler writes the signal number as a single byte
+ instead of a nul byte into the wakeup file descriptor. So it is possible to
+ wait more than one signal and know which signals were raised.
+
- Issue #8407: Add pthread_kill(), sigpending() and sigwait() functions to the
signal module.
diff --git a/Modules/signalmodule.c b/Modules/signalmodule.c
index 7285079..7e07b3e 100644
--- a/Modules/signalmodule.c
+++ b/Modules/signalmodule.c
@@ -176,6 +176,7 @@
static void
trip_signal(int sig_num)
{
+ unsigned char byte;
Handlers[sig_num].tripped = 1;
if (is_tripped)
return;
@@ -183,8 +184,10 @@
cleared in PyErr_CheckSignals() before .tripped. */
is_tripped = 1;
Py_AddPendingCall(checksignals_witharg, NULL);
- if (wakeup_fd != -1)
- write(wakeup_fd, "\0", 1);
+ if (wakeup_fd != -1) {
+ byte = (unsigned char)sig_num;
+ write(wakeup_fd, &byte, 1);
+ }
}
static void