Issue #12328: Under Windows, refactor handling of Ctrl-C events and

make _multiprocessing.win32.WaitForMultipleObjects interruptible when
the wait_flag parameter is false.  Patch by sbt.

4 files changed, 36 insertions, 70 deletions

diff --git a/Modules/_multiprocessing/multiprocessing.c b/Modules/_multiprocessing/multiprocessing.c
index 890b96d..ab2cd72 100644
--- a/Modules/_multiprocessing/multiprocessing.c
+++ b/Modules/_multiprocessing/multiprocessing.c
@@ -53,30 +53,6 @@ mp_SetError(PyObject *Type, int num)
 }
 
 
-/*
- * Windows only
- */
-
-#ifdef MS_WINDOWS
-
-/* On Windows we set an event to signal Ctrl-C; compare with timemodule.c */
-
-HANDLE sigint_event = NULL;
-
-static BOOL WINAPI
-ProcessingCtrlHandler(DWORD dwCtrlType)
-{
-    SetEvent(sigint_event);
-    return FALSE;
-}
-
-#endif /* MS_WINDOWS */
-
-
-/*
- * All platforms
- */
-
 static PyObject*
 multiprocessing_address_of_buffer(PyObject *self, PyObject *obj)
 {
@@ -165,17 +141,6 @@ PyInit__multiprocessing(void)
     if (!temp)
         return NULL;
     PyModule_AddObject(module, "win32", temp);
-
-    /* Initialize the event handle used to signal Ctrl-C */
-    sigint_event = CreateEvent(NULL, TRUE, FALSE, NULL);
-    if (!sigint_event) {
-        PyErr_SetFromWindowsErr(0);
-        return NULL;
-    }
-    if (!SetConsoleCtrlHandler(ProcessingCtrlHandler, TRUE)) {
-        PyErr_SetFromWindowsErr(0);
-        return NULL;
-    }
 #endif
 
     /* Add configuration macros */
diff --git a/Modules/_multiprocessing/multiprocessing.h b/Modules/_multiprocessing/multiprocessing.h
index ac0dfd7..e3de9ba 100644
--- a/Modules/_multiprocessing/multiprocessing.h
+++ b/Modules/_multiprocessing/multiprocessing.h
@@ -100,7 +100,6 @@ PyObject *mp_SetError(PyObject *Type, int num);
 extern PyObject *BufferTooShort;
 extern PyTypeObject SemLockType;
 extern PyTypeObject PipeConnectionType;
-extern HANDLE sigint_event;
 
 /*
  * Miscellaneous
diff --git a/Modules/_multiprocessing/semaphore.c b/Modules/_multiprocessing/semaphore.c
index 6749f23..e48936e 100644
--- a/Modules/_multiprocessing/semaphore.c
+++ b/Modules/_multiprocessing/semaphore.c
@@ -62,7 +62,8 @@ semlock_acquire(SemLockObject *self, PyObject *args, PyObject *kwds)
     int blocking = 1;
     double timeout;
     PyObject *timeout_obj = Py_None;
-    DWORD res, full_msecs, msecs, start, ticks;
+    DWORD res, full_msecs, nhandles;
+    HANDLE handles[2], sigint_event;
 
     static char *kwlist[] = {"block", "timeout", NULL};
 
@@ -96,53 +97,40 @@ semlock_acquire(SemLockObject *self, PyObject *args, PyObject *kwds)
         Py_RETURN_TRUE;
     }
 
-    /* check whether we can acquire without blocking */
+    /* check whether we can acquire without releasing the GIL and blocking */
     if (WaitForSingleObject(self->handle, 0) == WAIT_OBJECT_0) {
         self->last_tid = GetCurrentThreadId();
         ++self->count;
         Py_RETURN_TRUE;
     }
 
-    msecs = full_msecs;
-    start = GetTickCount();
-
-    for ( ; ; ) {
-        HANDLE handles[2] = {self->handle, sigint_event};
+    /* prepare list of handles */
+    nhandles = 0;
+    handles[nhandles++] = self->handle;
+    if (_PyOS_IsMainThread()) {
+        sigint_event = _PyOS_SigintEvent();
+        assert(sigint_event != NULL);
+        handles[nhandles++] = sigint_event;
+    }
 
-        /* do the wait */
-        Py_BEGIN_ALLOW_THREADS
+    /* do the wait */
+    Py_BEGIN_ALLOW_THREADS
+    if (sigint_event != NULL)
         ResetEvent(sigint_event);
-        res = WaitForMultipleObjects(2, handles, FALSE, msecs);
-        Py_END_ALLOW_THREADS
-
-        /* handle result */
-        if (res != WAIT_OBJECT_0 + 1)
-            break;
-
-        /* got SIGINT so give signal handler a chance to run */
-        Sleep(1);
-
-        /* if this is main thread let KeyboardInterrupt be raised */
-        if (PyErr_CheckSignals())
-            return NULL;
-
-        /* recalculate timeout */
-        if (msecs != INFINITE) {
-            ticks = GetTickCount();
-            if ((DWORD)(ticks - start) >= full_msecs)
-                Py_RETURN_FALSE;
-            msecs = full_msecs - (ticks - start);
-        }
-    }
+    res = WaitForMultipleObjects(nhandles, handles, FALSE, full_msecs);
+    Py_END_ALLOW_THREADS
 
     /* handle result */
     switch (res) {
     case WAIT_TIMEOUT:
         Py_RETURN_FALSE;
-    case WAIT_OBJECT_0:
+    case WAIT_OBJECT_0 + 0:
         self->last_tid = GetCurrentThreadId();
         ++self->count;
         Py_RETURN_TRUE;
+    case WAIT_OBJECT_0 + 1:
+        errno = EINTR;
+        return PyErr_SetFromErrno(PyExc_IOError);
     case WAIT_FAILED:
         return PyErr_SetFromWindowsErr(0);
     default:
diff --git a/Modules/_multiprocessing/win32_functions.c b/Modules/_multiprocessing/win32_functions.c
index c017b2a..ddc496d 100644
--- a/Modules/_multiprocessing/win32_functions.c
+++ b/Modules/_multiprocessing/win32_functions.c
@@ -679,6 +679,7 @@ win32_WaitForMultipleObjects(PyObject* self, PyObject* args)
     DWORD result;
     PyObject *handle_seq;
     HANDLE handles[MAXIMUM_WAIT_OBJECTS];
+    HANDLE sigint_event = NULL;
     Py_ssize_t nhandles, i;
     int wait_flag;
     int milliseconds = INFINITE;
@@ -696,10 +697,10 @@ win32_WaitForMultipleObjects(PyObject* self, PyObject* args)
     nhandles = PySequence_Length(handle_seq);
     if (nhandles == -1)
         return NULL;
-    if (nhandles < 0 || nhandles >= MAXIMUM_WAIT_OBJECTS) {
+    if (nhandles < 0 || nhandles >= MAXIMUM_WAIT_OBJECTS - 1) {
         PyErr_Format(PyExc_ValueError,
                      "need at most %zd handles, got a sequence of length %zd",
-                     MAXIMUM_WAIT_OBJECTS, nhandles);
+                     MAXIMUM_WAIT_OBJECTS - 1, nhandles);
         return NULL;
     }
     for (i = 0; i < nhandles; i++) {
@@ -711,14 +712,27 @@ win32_WaitForMultipleObjects(PyObject* self, PyObject* args)
             return NULL;
         handles[i] = h;
     }
+    /* If this is the main thread then make the wait interruptible
+       by Ctrl-C unless we are waiting for *all* handles */
+    if (!wait_flag && _PyOS_IsMainThread()) {
+        sigint_event = _PyOS_SigintEvent();
+        assert(sigint_event != NULL);
+        handles[nhandles++] = sigint_event;
+    }
 
     Py_BEGIN_ALLOW_THREADS
+    if (sigint_event != NULL)
+        ResetEvent(sigint_event);
     result = WaitForMultipleObjects((DWORD) nhandles, handles,
                                     (BOOL) wait_flag, (DWORD) milliseconds);
     Py_END_ALLOW_THREADS
 
     if (result == WAIT_FAILED)
         return PyErr_SetExcFromWindowsErr(PyExc_IOError, 0);
+    else if (sigint_event != NULL && result == WAIT_OBJECT_0 + nhandles - 1) {
+        errno = EINTR;
+        return PyErr_SetFromErrno(PyExc_IOError);
+    }
 
     return PyLong_FromLong((int) result);
 }