[3.5] bpo-33329: Fix multiprocessing regression on newer glibcs (GH-6575) (#12144)

csabella · pitrou · larryhastings · commit 8ec1fd11f2d5 · 2019-03-03T16:00:49.000-08:00
Starting with glibc 2.27.9000-xxx, sigaddset() can return EINVAL for some reserved signal numbers between 1 and NSIG. The `range(1, NSIG)` idiom is commonly used to select all signals for blocking with `pthread_sigmask`. So we ignore the sigaddset() return value until we expose sigfillset() to provide a better idiom. (cherry picked from commit 25038ec) Co-authored-by: Antoine Pitrou <pitrou@free.fr>
diff --git a/Misc/NEWS.d/next/Library/2018-04-23-13-21-39.bpo-33329.lQ-Eod.rst b/Misc/NEWS.d/next/Library/2018-04-23-13-21-39.bpo-33329.lQ-Eod.rst
@@ -0,0 +1 @@
+Fix multiprocessing regression on newer glibcs
diff --git a/Modules/signalmodule.c b/Modules/signalmodule.c
@@ -744,7 +744,6 @@ iterable_to_sigset(PyObject *iterable, sigset_t *mask)
     int result = -1;
     PyObject *iterator, *item;
     long signum;
-    int err;
 
     sigemptyset(mask);
 
@@ -766,11 +765,14 @@ iterable_to_sigset(PyObject *iterable, sigset_t *mask)
         Py_DECREF(item);
         if (signum == -1 && PyErr_Occurred())
             goto error;
-        if (0 < signum && signum < NSIG)
-            err = sigaddset(mask, (int)signum);
-        else
-            err = 1;
-        if (err) {
+        if (0 < signum && signum < NSIG) {
+            /* bpo-33329: ignore sigaddset() return value as it can fail
+             * for some reserved signals, but we want the `range(1, NSIG)`
+             * idiom to allow selecting all valid signals.
+             */
+            (void) sigaddset(mask, (int)signum);
+        }
+        else {
             PyErr_Format(PyExc_ValueError,
                          "signal number %ld out of range", signum);
             goto error;

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1 @@`
	`1`	`+Fix multiprocessing regression on newer glibcs`