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[3.10] bpo-44219: Release the GIL during isatty syscalls (GH-28250) #28255

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Merged
ambv merged 1 commit into from
Sep 9, 2021
Merged

[3.10] bpo-44219: Release the GIL during isatty syscalls (GH-28250) #28255

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4 changes: 4 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2021-09-09-10-32-33.bpo-44219.WiYyjz.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,4 @@
Release the GIL while performing ``isatty`` system calls on arbitrary file
descriptors. In particular, this affects :func:`os.isatty`,
:func:`os.device_encoding` and :class:`io.TextIOWrapper`. By extension,
:func:`io.open` in text mode is also affected.
2 changes: 2 additions & 0 deletions Modules/posixmodule.c
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Expand Up @@ -10062,9 +10062,11 @@ os_isatty_impl(PyObject *module, int fd)
/*[clinic end generated code: output=6a48c8b4e644ca00 input=08ce94aa1eaf7b5e]*/
{
int return_value;
Py_BEGIN_ALLOW_THREADS
_Py_BEGIN_SUPPRESS_IPH
return_value = isatty(fd);
_Py_END_SUPPRESS_IPH
Py_END_ALLOW_THREADS
return return_value;
}

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16 changes: 14 additions & 2 deletions Python/fileutils.c
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Expand Up @@ -67,9 +67,11 @@ PyObject *
_Py_device_encoding(int fd)
{
int valid;
Py_BEGIN_ALLOW_THREADS
_Py_BEGIN_SUPPRESS_IPH
valid = isatty(fd);
_Py_END_SUPPRESS_IPH
Py_END_ALLOW_THREADS
if (!valid)
Py_RETURN_NONE;

Expand Down Expand Up @@ -1776,12 +1778,22 @@ _Py_write_impl(int fd, const void *buf, size_t count, int gil_held)

_Py_BEGIN_SUPPRESS_IPH
#ifdef MS_WINDOWS
if (count > 32767 && isatty(fd)) {
if (count > 32767) {
/* Issue #11395: the Windows console returns an error (12: not
enough space error) on writing into stdout if stdout mode is
binary and the length is greater than 66,000 bytes (or less,
depending on heap usage). */
count = 32767;
if (gil_held) {
Py_BEGIN_ALLOW_THREADS
if (isatty(fd)) {
count = 32767;
}
Py_END_ALLOW_THREADS
} else {
if (isatty(fd)) {
count = 32767;
}
}
}
#endif
if (count > _PY_WRITE_MAX) {
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