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Slow createChild when limit of opened descriptors is set to high value #38

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Slow createChild when limit of opened descriptors is set to high value #38

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f9925ee
_createChild: try to close descriptors in /proc/self/fd or /dev/fd
trnila Mar 14, 2017
e122381
child.py close: check if system has /proc, check that FreeBSD has
trnila Mar 16, 2017
7fb604b
Removed unused import
trnila Mar 16, 2017
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33 changes: 25 additions & 8 deletions ptrace/debugger/child.py
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,8 @@
from os import (
fork, execvp, execvpe, waitpid,
close, dup2, pipe,
read, write, devnull, sysconf)
read, write, devnull, sysconf, listdir)
from os.path import isdir
from sys import exc_info
from traceback import format_exception
from ptrace.os_tools import RUNNING_WINDOWS
Expand Down Expand Up @@ -87,6 +88,27 @@ def _createParent(pid, errpipe_read):
raise child_exception


def _closeFdsExcept(fds, ignore_fds):
for fd in fds:
if fd not in ignore_fds:
try:
close(fd)
except OSError:
pass


def _closeFds(ignore_fds):
for path in ['/proc/self/fd', '/dev/fd']:
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@vstinner vstinner Mar 14, 2017

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/dev/fd is a symlink to /proc/self/fd. Is it really useful to test it?

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@trnila trnila Mar 15, 2017

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/dev/fd is symlink in Linux.
Other systems like BSD and Mac have /dev/fd.
On FreeBSD until fdescfs is mounted it contains only static descriptors 0, 1, 2 so there will be needed another test, otherwise it wont close any descriptor.
I will look at python subprocess.

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@vstinner vstinner Mar 15, 2017

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If you want to support BSD, see this test for FreeBSD:
https://github.com/python/cpython/blob/6c3d5274687c97f9c13800ad50e73e15b54f629d/Modules/_posixsubprocess.c#L87

try:
if isdir(path):
_closeFdsExcept([int(i) for i in listdir(path)], ignore_fds)
return
except OSError:
pass

_closeFdsExcept(range(0, MAXFD), ignore_fds)


def _createChild(arguments, no_stdout, env, errpipe_write):
# Child code
try:
Expand All @@ -95,13 +117,8 @@ def _createChild(arguments, no_stdout, env, errpipe_write):
raise ChildError(str(err))

# Close all files except 0, 1, 2 and errpipe_write
for fd in range(3, MAXFD):
if fd == errpipe_write:
continue
try:
close(fd)
except OSError:
pass
_closeFds([0, 1, 2, errpipe_write])

try:
_execChild(arguments, no_stdout, env)
except:
Expand Down