store GIL state in temp variable to safely keep it across generator yields (fixes ticket 803)

--HG--
extra : rebase_source : 5fd93f1cf2916c987bfc4a4d410bf4a77afb2ac9

Cython/Compiler/Code.py

@@ -1817,7 +1817,7 @@ class CCodeWriter(object):
 
     # GIL methods
 
-    def put_ensure_gil(self, declare_gilstate=True):
+    def put_ensure_gil(self, declare_gilstate=True, variable=None):
         """
         Acquire the GIL. The generated code is safe even when no PyThreadState
         has been allocated for this thread (for threads not initialized by
@@ -1827,32 +1827,42 @@ class CCodeWriter(object):
         self.globalstate.use_utility_code(
             UtilityCode.load_cached("ForceInitThreads", "ModuleSetupCode.c"))
         self.putln("#ifdef WITH_THREAD")
-        if declare_gilstate:
-            self.put("PyGILState_STATE ")
-        self.putln("__pyx_gilstate_save = PyGILState_Ensure();")
+        if not variable:
+            variable = '__pyx_gilstate_save'
+            if declare_gilstate:
+                self.put("PyGILState_STATE ")
+        self.putln("%s = PyGILState_Ensure();" % variable)
         self.putln("#endif")
 
-    def put_release_ensured_gil(self):
+    def put_release_ensured_gil(self, variable=None):
         """
         Releases the GIL, corresponds to `put_ensure_gil`.
         """
+        if not variable:
+            variable = '__pyx_gilstate_save'
         self.putln("#ifdef WITH_THREAD")
-        self.putln("PyGILState_Release(__pyx_gilstate_save);")
+        self.putln("PyGILState_Release(%s);" % variable)
         self.putln("#endif")
 
-    def put_acquire_gil(self):
+    def put_acquire_gil(self, variable=None):
         """
         Acquire the GIL. The thread's thread state must have been initialized
         by a previous `put_release_gil`
         """
+        self.putln("#ifdef WITH_THREAD")
+        if variable:
+            self.putln('_save = %s;' % variable)
         self.putln("Py_BLOCK_THREADS")
+        self.putln("#endif")
 
-    def put_release_gil(self):
+    def put_release_gil(self, variable=None):
         "Release the GIL, corresponds to `put_acquire_gil`."
         self.putln("#ifdef WITH_THREAD")
         self.putln("PyThreadState *_save = NULL;")
-        self.putln("#endif")
         self.putln("Py_UNBLOCK_THREADS")
+        if variable:
+            self.putln('%s = _save;' % variable)
+        self.putln("#endif")
 
     def declare_gilstate(self):
         self.putln("#ifdef WITH_THREAD")

Cython/Compiler/Nodes.py

@@ -6481,9 +6481,16 @@ class GILStatNode(NogilTryFinallyStatNode):
 
     def __init__(self, pos, state, body):
         self.state = state
+        if state == 'gil':
+            temp_type = PyrexTypes.c_gilstate_type
+        else:
+            temp_type = PyrexTypes.c_threadstate_ptr_type
+        import ExprNodes
+        self.state_temp = ExprNodes.TempNode(pos, temp_type)
         TryFinallyStatNode.__init__(self, pos,
-            body = body,
-            finally_clause = GILExitNode(pos, state = state))
+            body=body,
+            finally_clause=GILExitNode(
+                pos, state=state, state_temp=self.state_temp))
 
     def analyse_declarations(self, env):
         env._in_with_gil_block = (self.state == 'gil')
@@ -6504,13 +6511,16 @@ class GILStatNode(NogilTryFinallyStatNode):
     def generate_execution_code(self, code):
         code.mark_pos(self.pos)
         code.begin_block()
+        self.state_temp.allocate(code)
 
         if self.state == 'gil':
-            code.put_ensure_gil()
+            code.put_ensure_gil(variable=self.state_temp.result())
         else:
-            code.put_release_gil()
+            code.put_release_gil(variable=self.state_temp.result())
 
         TryFinallyStatNode.generate_execution_code(self, code)
+
+        self.state_temp.release(code)
         code.end_block()
 
 
@@ -6522,15 +6532,21 @@ class GILExitNode(StatNode):
     """
 
     child_attrs = []
+    state_temp = None
 
     def analyse_expressions(self, env):
         return self
 
     def generate_execution_code(self, code):
+        if self.state_temp:
+            variable = self.state_temp.result()
+        else:
+            variable = None
+
         if self.state == 'gil':
-            code.put_release_ensured_gil()
+            code.put_release_ensured_gil(variable)
         else:
-            code.put_acquire_gil()
+            code.put_acquire_gil(variable)
 
 
 class EnsureGILNode(GILExitNode):

Cython/Compiler/PyrexTypes.py

@@ -3453,6 +3453,10 @@ c_py_ssize_t_ptr_type =  CPtrType(c_py_ssize_t_type)
 c_ssize_t_ptr_type =  CPtrType(c_ssize_t_type)
 c_size_t_ptr_type =  CPtrType(c_size_t_type)
 
+# GIL state
+c_gilstate_type = CEnumType("PyGILState_STATE", "PyGILState_STATE", True)
+c_threadstate_type = CStructOrUnionType("PyThreadState", "struct", None, 1, "PyThreadState")
+c_threadstate_ptr_type = CPtrType(c_threadstate_type)
 
 # the Py_buffer type is defined in Builtin.py
 c_py_buffer_type = CStructOrUnionType("Py_buffer", "struct", None, 1, "Py_buffer")

tests/run/generators.pyx

@@ -318,3 +318,30 @@ def test_lambda(n):
     """
     for i in range(n):
         yield lambda : i
+
+
+def test_with_gil_section():
+    """
+    >>> list(test_with_gil_section())
+    [0, 1, 2]
+    """
+    cdef int i
+    with nogil:
+        for i in range(3):
+            with gil:
+                yield i
+
+
+def test_double_with_gil_section():
+    """
+    >>> list(test_double_with_gil_section())
+    [0, 1, 2, 3]
+    """
+    cdef int i,j
+    with nogil:
+        for i in range(2):
+            with gil:
+                with nogil:
+                    for j in range(2):
+                        with gil:
+                            yield i*2+j