Backport patch #1643738.

diff --git a/Misc/ACKS b/Misc/ACKS
index d39442eeb7257c9b9003240a9e25fee97f1119b5..f7765dcf4acbae18bd7da52b8d5725416bc6eba2 100644 (file)
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -216,6 +216,7 @@ Tadayoshi Funaba
 Gyro Funch
 Peter Funk
 Geoff Furnish
+Ulisses Furquim
 Lele Gaifax
 Yitzchak Gale
 Raymund Galvin

diff --git a/Modules/signalmodule.c b/Modules/signalmodule.c
index a729604a316bf4cb27376d880e54b12e32518c56..9d223d575a707f81a4952cf8962a0cacdf4d8fc5 100644 (file)
--- a/Modules/signalmodule.c
+++ b/Modules/signalmodule.c
@@ -75,7 +75,8 @@ static struct {
         PyObject *func;
 } Handlers[NSIG];
 
-static int is_tripped = 0; /* Speed up sigcheck() when none tripped */
+/* Speed up sigcheck() when none tripped */
+static volatile sig_atomic_t is_tripped = 0;
 
 static PyObject *DefaultHandler;
 static PyObject *IgnoreHandler;
@@ -122,8 +123,10 @@ signal_handler(int sig_num)
        /* See NOTES section above */
        if (getpid() == main_pid) {
 #endif
-               is_tripped++;
                Handlers[sig_num].tripped = 1;
+                /* Set is_tripped after setting .tripped, as it gets
+                   cleared in PyErr_CheckSignals() before .tripped. */
+               is_tripped = 1;
                Py_AddPendingCall(checksignals_witharg, NULL);
 #ifdef WITH_THREAD
        }
@@ -597,13 +600,31 @@ PyErr_CheckSignals(void)
 
        if (!is_tripped)
                return 0;
+
 #ifdef WITH_THREAD
        if (PyThread_get_thread_ident() != main_thread)
                return 0;
 #endif
+
+       /*
+        * The is_stripped variable is meant to speed up the calls to
+        * PyErr_CheckSignals (both directly or via pending calls) when no
+        * signal has arrived. This variable is set to 1 when a signal arrives
+        * and it is set to 0 here, when we know some signals arrived. This way
+        * we can run the registered handlers with no signals blocked.
+        *
+        * NOTE: with this approach we can have a situation where is_tripped is
+        *       1 but we have no more signals to handle (Handlers[i].tripped
+        *       is 0 for every signal i). This won't do us any harm (except
+        *       we're gonna spent some cycles for nothing). This happens when
+        *       we receive a signal i after we zero is_tripped and before we
+        *       check Handlers[i].tripped.
+        */
+       is_tripped = 0;
+
        if (!(f = (PyObject *)PyEval_GetFrame()))
                f = Py_None;
-       
+
        for (i = 1; i < NSIG; i++) {
                if (Handlers[i].tripped) {
                        PyObject *result = NULL;
@@ -621,7 +642,7 @@ PyErr_CheckSignals(void)
                        Py_DECREF(result);
                }
        }
-       is_tripped = 0;
+
        return 0;
 }
 
@@ -632,7 +653,7 @@ PyErr_CheckSignals(void)
 void
 PyErr_SetInterrupt(void)
 {
-       is_tripped++;
+       is_tripped = 1;
        Handlers[SIGINT].tripped = 1;
        Py_AddPendingCall((int (*)(void *))PyErr_CheckSignals, NULL);
 }