8000 [3.6] bpo-33021: Release the GIL during fstat() calls (GH-6019) by miss-islington · Pull Request #6160 · python/cpython · GitHub
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[3.6] bpo-33021: Release the GIL during fstat() calls (GH-6019) #6160

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Mar 20, 2018
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Release the GIL during fstat() calls, avoiding hang of all threads when
calling mmap.mmap(), os.urandom(), and random.seed(). Patch by Nir Soffer.
11 changes: 9 additions & 2 deletions Modules/mmapmodule.c
Original file line number Diff line number Diff line change
Expand Up @@ -1078,6 +1078,7 @@ static PyObject *
new_mmap_object(PyTypeObject *type, PyObject *args, PyObject *kwdict)
{
struct _Py_stat_struct status;
int fstat_result = -1;
mmap_object *m_obj;
Py_ssize_t map_size;
off_t offset = 0;
Expand Down Expand Up @@ -1143,8 +1144,14 @@ new_mmap_object(PyTypeObject *type, PyObject *args, PyObject *kwdict)
if (fd != -1)
(void)fcntl(fd, F_FULLFSYNC);
#endif
if (fd != -1 && _Py_fstat_noraise(fd, &status) == 0
&& S_ISREG(status.st_mode)) {

if (fd != -1) {
Py_BEGIN_ALLOW_THREADS
fstat_result = _Py_fstat_noraise(fd, &status);
Py_END_ALLOW_THREADS
}

if (fd != -1 && fstat_result == 0 && S_ISREG(status.st_mode)) {
if (map_size == 0) {
if (status.st_size == 0) {
PyErr_SetString(PyExc_ValueError,
Expand Down
7 changes: 6 additions & 1 deletion Python/random.c
Original file line number Diff line number Diff line change
Expand Up @@ -301,10 +301,15 @@ dev_urandom(char *buffer, Py_ssize_t size, int raise)

if (raise) {
struct _Py_stat_struct st;
int fstat_result;

if (urandom_cache.fd >= 0) {
Py_BEGIN_ALLOW_THREADS
fstat_result = _Py_fstat_noraise(urandom_cache.fd, &st);
Py_END_ALLOW_THREADS

/* Does the fd point to the same thing as before? (issue #21207) */
if (_Py_fstat_noraise(urandom_cache.fd, &st)
if (fstat_result
|| st.st_dev != urandom_cache.st_dev
|| st.st_ino != urandom_cache.st_ino) {
/* Something changed: forget the cached fd (but don't close it,
Expand Down
0