Mercurial > cpython-lru_cache-weakref
diff Python/import.c @ 56008:1ad9f2bda20a 2.6
Merged revisions 74841 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/trunk
........
r74841 | thomas.wouters | 2009-09-16 12:55:54 -0700 (Wed, 16 Sep 2009) | 23 lines
Fix issue #1590864, multiple threads and fork() can cause deadlocks, by
acquiring the import lock around fork() calls. This prevents other threads
from having that lock while the fork happens, and is the recommended way of
dealing with such issues. There are two other locks we care about, the GIL
and the Thread Local Storage lock. The GIL is obviously held when calling
Python functions like os.fork(), and the TLS lock is explicitly reallocated
instead, while also deleting now-orphaned TLS data.
This only fixes calls to os.fork(), not extension modules or embedding
programs calling C's fork() directly. Solving that requires a new set of API
functions, and possibly a rewrite of the Python/thread_*.c mess. Add a
warning explaining the problem to the documentation in the mean time.
This also changes behaviour a little on AIX. Before, AIX (but only AIX) was
getting the import lock reallocated, seemingly to avoid this very same
problem. This is not the right approach, because the import lock is a
re-entrant one, and reallocating would do the wrong thing when forking while
holding the import lock.
Will backport to 2.6, minus the tiny AIX behaviour change.
........
| author | Thomas Wouters <thomas@python.org> |
|---|---|
| date | Wed, 16 Sep 2009 20:06:36 +0000 |
| parents | f20705875e80 |
| children | d5f50ae4f1f7 |
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--- a/Python/import.c Wed Sep 16 13:31:18 2009 +0000 +++ b/Python/import.c Wed Sep 16 20:06:36 2009 +0000 @@ -256,8 +256,8 @@ static long import_lock_thread = -1; static int import_lock_level = 0; -static void -lock_import(void) +void +_PyImport_AcquireLock(void) { long me = PyThread_get_thread_ident(); if (me == -1) @@ -281,8 +281,8 @@ import_lock_level = 1; } -static int -unlock_import(void) +int +_PyImport_ReleaseLock(void) { long me = PyThread_get_thread_ident(); if (me == -1 || import_lock == NULL) @@ -309,11 +309,6 @@ #endif } -#else - -#define lock_import() -#define unlock_import() 0 - #endif static PyObject * @@ -330,7 +325,7 @@ imp_acquire_lock(PyObject *self, PyObject *noargs) { #ifdef WITH_THREAD - lock_import(); + _PyImport_AcquireLock(); #endif Py_INCREF(Py_None); return Py_None; @@ -340,7 +335,7 @@ imp_release_lock(PyObject *self, PyObject *noargs) { #ifdef WITH_THREAD - if (unlock_import() < 0) { + if (_PyImport_ReleaseLock() < 0) { PyErr_SetString(PyExc_RuntimeError, "not holding the import lock"); return NULL; @@ -2183,9 +2178,9 @@ PyObject *fromlist, int level) { PyObject *result; - lock_import(); + _PyImport_AcquireLock(); result = import_module_level(name, globals, locals, fromlist, level); - if (unlock_import() < 0) { + if (_PyImport_ReleaseLock() < 0) { Py_XDECREF(result); PyErr_SetString(PyExc_RuntimeError, "not holding the import lock");