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Issue #9260: A finer-grained import lock.

Browse source 
Most of the import sequence now uses per-module locks rather than the
global import lock, eliminating well-known issues with threads and imports.
This commit is contained in:
Antoine Pitrou 2012-05-17 18:55:59 +02:00
parent 5cec9d2ae5
commit ea3eb88bca
12 changed files with 3777 additions and 3041 deletions
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88
Python/import.c
View file

@ -1370,47 +1370,7 @@ PyImport_ImportModule(const char *name)
PyObject *
PyImport_ImportModuleNoBlock(const char *name)
{
PyObject *nameobj, *modules, *result;
#ifdef WITH_THREAD
long me;
#endif
/* Try to get the module from sys.modules[name] */
modules = PyImport_GetModuleDict();
if (modules == NULL)
return NULL;
nameobj = PyUnicode_FromString(name);
if (nameobj == NULL)
return NULL;
result = PyDict_GetItem(modules, nameobj);
if (result != NULL) {
Py_DECREF(nameobj);
Py_INCREF(result);
return result;
}
PyErr_Clear();
#ifdef WITH_THREAD
/* check the import lock
* me might be -1 but I ignore the error here, the lock function
* takes care of the problem */
me = PyThread_get_thread_ident();
if (import_lock_thread == -1 || import_lock_thread == me) {
/* no thread or me is holding the lock */
result = PyImport_Import(nameobj);
}
else {
PyErr_Format(PyExc_ImportError,
"Failed to import %R because the import lock"
"is held by another thread.",
nameobj);
result = NULL;
}
#else
result = PyImport_Import(nameobj);
#endif
Py_DECREF(nameobj);
return result;
return PyImport_ImportModule(name);
}
@ -1420,11 +1380,13 @@ PyImport_ImportModuleLevelObject(PyObject *name, PyObject *given_globals,
int level)
{
_Py_IDENTIFIER(__import__);
_Py_IDENTIFIER(__initializing__);
_Py_IDENTIFIER(__package__);
_Py_IDENTIFIER(__path__);
_Py_IDENTIFIER(__name__);
_Py_IDENTIFIER(_find_and_load);
_Py_IDENTIFIER(_handle_fromlist);
_Py_IDENTIFIER(_lock_unlock_module);
_Py_static_string(single_dot, ".");
PyObject *abs_name = NULL;
PyObject *builtins_import = NULL;
@ -1607,16 +1569,48 @@ PyImport_ImportModuleLevelObject(PyObject *name, PyObject *given_globals,
goto error_with_unlock;
}
else if (mod != NULL) {
PyObject *value;
int initializing = 0;
Py_INCREF(mod);
/* Only call _bootstrap._lock_unlock_module() if __initializing__ is true. */
value = _PyObject_GetAttrId(mod, &PyId___initializing__);
if (value == NULL)
PyErr_Clear();
else {
initializing = PyObject_IsTrue(value);
Py_DECREF(value);
if (initializing == -1)
PyErr_Clear();
}
if (initializing > 0) {
/* _bootstrap._lock_unlock_module() releases the import lock */
value = _PyObject_CallMethodObjIdArgs(interp->importlib,
&PyId__lock_unlock_module, abs_name,
NULL);
if (value == NULL)
goto error;
Py_DECREF(value);
}
else {
#ifdef WITH_THREAD
if (_PyImport_ReleaseLock() < 0) {
PyErr_SetString(PyExc_RuntimeError, "not holding the import lock");
goto error;
}
#endif
}
}
else {
/* _bootstrap._find_and_load() releases the import lock */
mod = _PyObject_CallMethodObjIdArgs(interp->importlib,
&PyId__find_and_load, abs_name,
builtins_import, NULL);
if (mod == NULL) {
goto error_with_unlock;
goto error;
}
}
/* From now on we don't hold the import lock anymore. */
if (PyObject_Not(fromlist)) {
if (level == 0 || PyUnicode_GET_LENGTH(name) > 0) {
@ -1625,12 +1619,12 @@ PyImport_ImportModuleLevelObject(PyObject *name, PyObject *given_globals,
PyObject *borrowed_dot = _PyUnicode_FromId(&single_dot);
if (borrowed_dot == NULL) {
goto error_with_unlock;
goto error;
}
partition = PyUnicode_Partition(name, borrowed_dot);
if (partition == NULL) {
goto error_with_unlock;
goto error;
}
if (PyUnicode_GET_LENGTH(PyTuple_GET_ITEM(partition, 1)) == 0) {
@ -1638,7 +1632,7 @@ PyImport_ImportModuleLevelObject(PyObject *name, PyObject *given_globals,
Py_DECREF(partition);
final_mod = mod;
Py_INCREF(mod);
goto exit_with_unlock;
goto error;
}
front = PyTuple_GET_ITEM(partition, 0);
@ -1657,7 +1651,7 @@ PyImport_ImportModuleLevelObject(PyObject *name, PyObject *given_globals,
abs_name_len - cut_off);
Py_DECREF(front);
if (to_return == NULL) {
goto error_with_unlock;
goto error;
}
final_mod = PyDict_GetItem(interp->modules, to_return);
@ -1683,8 +1677,8 @@ PyImport_ImportModuleLevelObject(PyObject *name, PyObject *given_globals,
fromlist, builtins_import,
NULL);
}
goto error;
exit_with_unlock:
error_with_unlock:
#ifdef WITH_THREAD
if (_PyImport_ReleaseLock() < 0) {