rewrite fork handler into c - no python runtime required then

Author: grungy-ado

tests/test_process_spawning.py

@@ -92,12 +92,12 @@ def spawn_process():
                               ctypes.c_size_t, ctypes.c_void_p)
             fread.restype = ctypes.c_size_t
 
-            for iteration in range(10000):
+            for iteration in range(1000):
                 t = Thread(target=run_echo,
                            args=(popen, fread, pclose),
                            daemon=True)
                 t.start()
-                t.join(timeout=20.0)
+                t.join(timeout=10.0)
                 if t.is_alive():
                     raise Exception('process freeze detected at {}'
                                     .format(iteration))

uvloop/handles/process.pyx

@@ -28,6 +28,7 @@ cdef class UVProcess(UVHandle):
 
         global __forking
         global __forking_loop
+        global __forkHandler
 
         cdef int err
 
@@ -76,6 +77,7 @@ cdef class UVProcess(UVHandle):
             loop.active_process_handler = self
             __forking = 1
             __forking_loop = loop
+            __forkHandler = <OnForkHandler>&__get_fork_handler
 
             PyOS_BeforeFork()
 
@@ -85,6 +87,7 @@ cdef class UVProcess(UVHandle):
 
             __forking = 0
             __forking_loop = None
+            __forkHandler = NULL
             loop.active_process_handler = None
 
             PyOS_AfterFork_Parent()

uvloop/includes/fork_handler.h

@@ -0,0 +1,15 @@
+
+typedef void (*OnForkHandler)();
+
+OnForkHandler __forkHandler = NULL;
+
+/* Auxiliary function to call global fork handler if defined.
+
+Note: Fork handler needs to be in C (not cython) otherwise it would require
+GIL to be present, but some forks can exec non-python processes.
+*/
+void handleAtFork() {
+    if (__forkHandler != NULL) {
+        __forkHandler();
+    }
+}

uvloop/includes/system.pxd

@@ -59,12 +59,12 @@ cdef extern from "unistd.h" nogil:
     void _exit(int status)
 
 
-cdef extern from "pthread.h" nogil:
+cdef extern from "pthread.h":
 
     int pthread_atfork(
-        void (*prepare)() nogil,
-        void (*parent)() nogil,
-        void (*child)() nogil)
+        void (*prepare)(),
+        void (*parent)(),
+        void (*child)())
 
 
 cdef extern from "includes/compat.h" nogil:

uvloop/loop.pyx

@@ -3117,21 +3117,21 @@ cdef vint __atfork_installed = 0
 cdef vint __forking = 0
 cdef Loop __forking_loop = None
 
+cdef extern from "includes/fork_handler.h":
 
-cdef void __atfork_child() nogil:
-    # See CPython/posixmodule.c for details
-    global __forking
+    ctypedef void (*OnForkHandler)()
+    cdef OnForkHandler __forkHandler
+    void handleAtFork()
 
-    if __forking:
-        __run_fork_handler()
+cdef void __get_fork_handler() nogil:
+    global __forking
+    global __forking_loop
 
-cdef void __run_fork_handler() nogil:
     with gil:
-        if (__forking_loop is not None and
+        if (__forking and __forking_loop is not None and
                 __forking_loop.active_process_handler is not None):
             __forking_loop.active_process_handler._after_fork()
 
-
 cdef __install_atfork():
     global __atfork_installed
     if __atfork_installed:
@@ -3140,7 +3140,7 @@ cdef __install_atfork():
 
     cdef int err
 
-    err = system.pthread_atfork(NULL, NULL, &__atfork_child)
+    err = system.pthread_atfork(NULL, NULL, &handleAtFork)
     if err:
         __atfork_installed = 0
         raise convert_error(-err)