#27647: Django runserver segfaults with autoreload enabled on Windows 10
-------------------------------------+-------------------------------------
Reporter: Aleksi Häkli | Owner: nobody
Type: Uncategorized | Status: new
Component: Core (Management | Version: 1.10
commands) |
Severity: Normal | Resolution:
Keywords: runserver | Triage Stage:
autoreload autoreload.py noreload | Unreviewed
restart_with_reloader segfault |
segmentation fault ucrtbase.dll |
threading |
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by Aleksi Häkli):
* has_patch: 0 => 1
Old description:
> Django `runserver` segfaults with autoreload enabled on the `os.spawnve`
> call on Python 3.5 and Python 3.6.
>
> The problem is apparently on this line:
>
> https://github.com/django/django/blob/b79fc11d730b5beff92e9dd8853a61524cdeffe3/django/utils/autoreload.py#L290
>
> Python documentation states that the ''`os.spawnve` function is NOT
> thread-safe on Windows'' and that the `subprocess` module should be used
> instead.
>
> I hence suspect that a thread that is spawned on reload makes a memory
> violation and causes a segmentation fault which kills off the server.
>
> I propose that `autoreload.py` be refactored to use a thread-safe
> implementation either by the subprocess module or by other alternative
> implementation.
>
> ----
>
> **Discussion**
>
> I have run Django 1.8, 1.9 and 1.10 on multiple Python versions on top of
> Windows 10 64-bit on different computers. Starting with Python 3.5 and
> Python 3.6 I have reproduced a consistent segmentation fault on the
> `runserver` command with both 32-bit and 64-bit Pythons. This has
> happened for several months. `python manage.py migrate` and other
> commands work well and consistently. `python manage.py runserver` is the
> ONLY command that segmentation faults and does NOT do this with
> `--noreload` option. Today I dug a bit deeper on the cause of the
> segmentation fault.
>
> As a note, I have also run Django on top of Python 3.4 and at least the
> 32-bit distribution, for whatever reason, tends not to cause errors like
> these. This is, however, just my butt-feeling, as we say in Finland, and
> I have not measured the stuff for a small while.
>
> ----
>
> **Demonstration**
>
> This example is run with `virtualenvwrapper` installed virtual
> environment with Python 3.6.0 32-bit with the latest available `Microsoft
> Visual C++ 2015 Redistributable (x86) - 14.0.23026` downloaded and
> patched today on Windows 10 64-bit, so I expect my computer is up to
> date. Program versions and tracebacks following.
>
> ----
>
> **Python installation**
>
> {{{
> USER@COMPUTER MINGW32 ~
> $ python
> Python 3.6.0 (v3.6.0:41df79263a11, Dec 23 2016, 07:18:10) [MSC v.1900 32
> bit (Intel)] on win32
> }}}
>
> {{{
> USER@COMPUTER MINGW32 ~
> $ pip freeze # global dependencies
> pbr==1.10.0
> six==1.10.0
> stevedore==1.19.1
> virtualenv==15.1.0
> virtualenv-clone==0.2.6
> virtualenvwrapper==4.7.2
> }}}
>
> ----
>
> **`gdb` traceback** on the error which identifies `ucrtbase.dll` and
> `wdupenv_s` as the evil party:
>
> {{{
> (demo)
> USER@COMPUTER MINGW32 ~/Documents/projects/demo (master)
> $ gdb python
> GNU gdb (GDB) 7.6.1
> Copyright (C) 2013 Free Software Foundation, Inc.
> License GPLv3+: GNU GPL version 3 or later
> <http://gnu.org/licenses/gpl.html>
> This is free software: you are free to change and redistribute it.
> There is NO WARRANTY, to the extent permitted by law. Type "show
> copying"
> and "show warranty" for details.
> This GDB was configured as "mingw32".
> For bug reporting instructions, please see:
> <http://www.gnu.org/software/gdb/bugs/>...
> Reading symbols from
> C:\Users\USER\.virtualenvs\demo\Scripts\python.exe...(no debugging
> symbols found)...done.
> (gdb) run manage.py runserver
> Starting program: C:\Users\USER\.virtualenvs\demo\Scripts/python.exe
> manage.py runserver
> [New Thread 6876.0x2a18]
> [New Thread 6876.0x13f4]
> [New Thread 6876.0x25d0]
> [New Thread 6876.0x2a64]
>
> Program received signal SIGSEGV, Segmentation fault.
> 0x77cebd9e in wdupenv_s () from C:\WINDOWS\SysWoW64\ucrtbase.dll
> (gdb)
> }}}
>
> ----
>
> **`faulthandler` traceback** with a vanilla `manage.py` script with
> `faulthandler` enabled with `faulthandler.enable()` which traces the
> Django error back to `autoreload.py`:
>
> {{{
> (demo)
> USER@COMPUTER MINGW32 ~/Documents/projects/demo (master)
> $ python manage.py runserver
>
> Windows fatal exception: access violation
>
> Current thread 0x00001b6c (most recent call first):
> File "C:\Users\USER\.virtualenvs\demo\lib\site-
> packages\django\utils\autoreload.py", line 290 in restart_with_reloader
> File "C:\Users\USER\.virtualenvs\demo\lib\site-
> packages\django\utils\autoreload.py", line 304 in python_reloader
> File "C:\Users\USER\.virtualenvs\demo\lib\site-
> packages\django\utils\autoreload.py", line 333 in main
> File "C:\Users\USER\.virtualenvs\demo\lib\site-
> packages\django\core\management\commands\runserver.py", line 106 in run
> File "C:\Users\USER\.virtualenvs\demo\lib\site-
> packages\django\core\management\commands\runserver.py", line 97 in handle
> File "C:\Users\USER\.virtualenvs\demo\lib\site-
> packages\django\core\management\base.py", line 345 in execute
> File "C:\Users\USER\.virtualenvs\demo\lib\site-
> packages\django\core\management\commands\runserver.py", line 58 in
> execute
> File "C:\Users\USER\.virtualenvs\demo\lib\site-
> packages\django\core\management\base.py", line 294 in run_from_argv
> File "C:\Users\USER\.virtualenvs\demo\lib\site-
> packages\django\core\management\__init__.py", line 359 in execute
> File "C:\Users\USER\.virtualenvs\demo\lib\site-
> packages\django\core\management\__init__.py", line 367 in
> execute_from_command_line
> File "manage.py", line 26 in <module>
> Segmentation fault
> }}}
New description:
Django `runserver` segfaults with autoreload enabled on the `os.spawnve`
call on Python 3.5 and Python 3.6.
The problem is apparently on this line:
https://github.com/django/django/blob/b79fc11d730b5beff92e9dd8853a61524cdeffe3/django/utils/autoreload.py#L290
Python documentation states that the ''`os.spawnve` function is NOT
thread-safe on Windows'' and that the `subprocess` module should be used
instead.
I hence suspect that a thread that is spawned on reload makes a memory
violation and causes a segmentation fault which kills off the server.
I propose that `autoreload.py` be refactored to use a thread-safe
implementation either by the subprocess module or by other alternative
implementation.
**Update**: I added a preliminary patch implementation up for review that
implements a fix for Python 2.4+ in
[https://github.com/django/djangopull/7748] by using the recommended
`subprocess.call()` instead of the non-thread-safe `os.spawnve()` which
was added in 2005.
----
**Discussion**
I have run Django 1.8, 1.9 and 1.10 on multiple Python versions on top of
Windows 10 64-bit on different computers. Starting with Python 3.5 and
Python 3.6 I have reproduced a consistent segmentation fault on the
`runserver` command with both 32-bit and 64-bit Pythons. This has happened
for several months. `python manage.py migrate` and other commands work
well and consistently. `python manage.py runserver` is the ONLY command
that segmentation faults and does NOT do this with `--noreload` option.
Today I dug a bit deeper on the cause of the segmentation fault.
As a note, I have also run Django on top of Python 3.4 and at least the
32-bit distribution, for whatever reason, tends not to cause errors like
these. This is, however, just my butt-feeling, as we say in Finland, and I
have not measured the stuff for a small while.
----
**Demonstration**
This example is run with `virtualenvwrapper` installed virtual environment
with Python 3.6.0 32-bit with the latest available `Microsoft Visual C++
2015 Redistributable (x86) - 14.0.23026` downloaded and patched today on
Windows 10 64-bit, so I expect my computer is up to date. Program versions
and tracebacks following.
----
**Python installation**
{{{
USER@COMPUTER MINGW32 ~
$ python
Python 3.6.0 (v3.6.0:41df79263a11, Dec 23 2016, 07:18:10) [MSC v.1900 32
bit (Intel)] on win32
}}}
{{{
USER@COMPUTER MINGW32 ~
$ pip freeze # global dependencies
pbr==1.10.0
six==1.10.0
stevedore==1.19.1
virtualenv==15.1.0
virtualenv-clone==0.2.6
virtualenvwrapper==4.7.2
}}}
----
**`gdb` traceback** on the error which identifies `ucrtbase.dll` and
`wdupenv_s` as the evil party:
{{{
(demo)
USER@COMPUTER MINGW32 ~/Documents/projects/demo (master)
$ gdb python
GNU gdb (GDB) 7.6.1
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later
<http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law. Type "show copying"
and "show warranty" for details.
This GDB was configured as "mingw32".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from
C:\Users\USER\.virtualenvs\demo\Scripts\python.exe...(no debugging symbols
found)...done.
(gdb) run manage.py runserver
Starting program: C:\Users\USER\.virtualenvs\demo\Scripts/python.exe
manage.py runserver
[New Thread 6876.0x2a18]
[New Thread 6876.0x13f4]
[New Thread 6876.0x25d0]
[New Thread 6876.0x2a64]
Program received signal SIGSEGV, Segmentation fault.
0x77cebd9e in wdupenv_s () from C:\WINDOWS\SysWoW64\ucrtbase.dll
(gdb)
}}}
----
**`faulthandler` traceback** with a vanilla `manage.py` script with
`faulthandler` enabled with `faulthandler.enable()` which traces the
Django error back to `autoreload.py`:
{{{
(demo)
USER@COMPUTER MINGW32 ~/Documents/projects/demo (master)
$ python manage.py runserver
Windows fatal exception: access violation
Current thread 0x00001b6c (most recent call first):
File "C:\Users\USER\.virtualenvs\demo\lib\site-
packages\django\utils\autoreload.py", line 290 in restart_with_reloader
File "C:\Users\USER\.virtualenvs\demo\lib\site-
packages\django\utils\autoreload.py", line 304 in python_reloader
File "C:\Users\USER\.virtualenvs\demo\lib\site-
packages\django\utils\autoreload.py", line 333 in main
File "C:\Users\USER\.virtualenvs\demo\lib\site-
packages\django\core\management\commands\runserver.py", line 106 in run
File "C:\Users\USER\.virtualenvs\demo\lib\site-
packages\django\core\management\commands\runserver.py", line 97 in handle
File "C:\Users\USER\.virtualenvs\demo\lib\site-
packages\django\core\management\base.py", line 345 in execute
File "C:\Users\USER\.virtualenvs\demo\lib\site-
packages\django\core\management\commands\runserver.py", line 58 in execute
File "C:\Users\USER\.virtualenvs\demo\lib\site-
packages\django\core\management\base.py", line 294 in run_from_argv
File "C:\Users\USER\.virtualenvs\demo\lib\site-
packages\django\core\management\__init__.py", line 359 in execute
File "C:\Users\USER\.virtualenvs\demo\lib\site-
packages\django\core\management\__init__.py", line 367 in
execute_from_command_line
File "manage.py", line 26 in <module>
Segmentation fault
}}}
--
Comment:
Add PR link to GitHub.
--
Ticket URL: <https://code.djangoproject.com/ticket/27647#comment:4>
Django <https://code.djangoproject.com/>
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