Merge for #27083

1 files changed, 29 insertions, 5 deletions

diff --git a/Python/fileutils.c b/Python/fileutils.c
index 23eed71321..06531d9726 100644
--- a/Python/fileutils.c
+++ b/Python/fileutils.c
@@ -683,6 +683,10 @@ _Py_fstat(int fd, struct _Py_stat_struct *status)
 {
     int res;
 
+#ifdef WITH_THREAD
+    assert(PyGILState_Check());
+#endif
+
     Py_BEGIN_ALLOW_THREADS
     res = _Py_fstat_noraise(fd, status);
     Py_END_ALLOW_THREADS
@@ -794,7 +798,7 @@ set_inheritable(int fd, int inheritable, int raise, int *atomic_flag_works)
     int request;
     int err;
 #endif
-    int flags;
+    int flags, new_flags;
     int res;
 #endif
 
@@ -885,10 +889,18 @@ set_inheritable(int fd, int inheritable, int raise, int *atomic_flag_works)
         return -1;
     }
 
-    if (inheritable)
-        flags &= ~FD_CLOEXEC;
-    else
-        flags |= FD_CLOEXEC;
+    if (inheritable) {
+        new_flags = flags & ~FD_CLOEXEC;
+    }
+    else {
+        new_flags = flags | FD_CLOEXEC;
+    }
+
+    if (new_flags == flags) {
+        /* FD_CLOEXEC flag already set/cleared: nothing to do */
+        return 0;
+    }
+
     res = fcntl(fd, F_SETFD, flags);
     if (res < 0) {
         if (raise)
@@ -1169,6 +1181,10 @@ _Py_read(int fd, void *buf, size_t count)
     int err;
     int async_err = 0;
 
+#ifdef WITH_THREAD
+    assert(PyGILState_Check());
+#endif
+
     /* _Py_read() must not be called with an exception set, otherwise the
      * caller may think that read() was interrupted by a signal and the signal
      * handler raised an exception. */
@@ -1324,6 +1340,10 @@ _Py_write_impl(int fd, const void *buf, size_t count, int gil_held)
 Py_ssize_t
 _Py_write(int fd, const void *buf, size_t count)
 {
+#ifdef WITH_THREAD
+    assert(PyGILState_Check());
+#endif
+
     /* _Py_write() must not be called with an exception set, otherwise the
      * caller may think that write() was interrupted by a signal and the signal
      * handler raised an exception. */
@@ -1473,6 +1493,10 @@ _Py_dup(int fd)
     DWORD ftype;
 #endif
 
+#ifdef WITH_THREAD
+    assert(PyGILState_Check());
+#endif
+
     if (!_PyVerify_fd(fd)) {
         PyErr_SetFromErrno(PyExc_OSError);
         return -1;