On Linux where the `subprocess` module can use the `vfork` syscall for
faster spawning, prevent the parent process from blocking other threads
by dropping the GIL while it waits for the vfork'ed child process `exec`
outcome. This prevents spawning a binary from a slow filesystem from
blocking the rest of the application.
Fixes#104372.
In line 1627, the end of the sentence reads "only that that it may be." but it should read "only that it may be" (or alternatively "only that that may be").
Co-authored-by: Hugo Gabriel Eyherabide <hugogabriel.eyherabide@gmail.com>
* Note that Popen attributes aren't meant to be set by users by rewording the text about the attributes.
* Also update some universal_newlines references to mention the modern text parameter name while in the area.
Co-authored-by: Gregory P. Smith <greg@krypto.org>
* Update description of stdout, stderr, and stdin.
Changes:
- Move the ``None`` option (which is default) to the front of the list
of input options
- Move the ``None`` option description up to make the default behavior
more clear (No redirection)
- Remove mention of Child File Descriptors from ``None`` option description
One more thing that can help prevent people from using `preexec_fn`.
Also adds conditional skips to two tests exposing ASAN flakiness on the Ubuntu 20.04 Address Sanitizer Github CI system. When that build is run on more modern systems the "problem" does not show up. It seems ASAN implementation related.
Co-authored-by: Zackery Spytz <zspytz@gmail.com>
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
Just in case there is ever an issue with _posixsubprocess's use of
vfork() due to the complexity of using it properly and potential
directions that Linux platforms where it defaults to on could take, this
adds a failsafe so that users can disable its use entirely by setting
a global flag.
No known reason to disable it exists. But it'd be a shame to encounter
one and not be able to use CPython without patching and rebuilding it.
See the linked issue for some discussion on reasoning.
Also documents the existing way to disable posix_spawn.
* Document os-system, subprocess Patch
* Update Doc/library/os.rst
Co-authored-by: Ken Jin <28750310+Fidget-Spinner@users.noreply.github.com>
Co-authored-by: Ken Jin <28750310+Fidget-Spinner@users.noreply.github.com>
When the modern text= spelling of the universal_newlines= parameter was added
for Python 3.7, check_output's special case around input=None was overlooked.
So it behaved differently with universal_newlines=True vs text=True. This
reconciles the behavior to be consistent and adds a test to guarantee it.
Also clarifies the existing check_output documentation.
Co-authored-by: Alexey Izbyshev <izbyshev@ispras.ru>
The issue being resolved is shown in the 3.10 docs (if you select docs for older versions you won't see a visual glitch).
The newer sphinx version that produces the 3.10 docs doesn't treat the backslash to escape things in some situations it previously did.
Added a note in the `subprocess` docs that recommend using `shlex.quote` without mentioning that this is only applicable to Unix.
Also added a warning straight into the `shlex` docs since it only says "for simple syntaxes resembling that of the Unix shell" and says using `quote` plugs the security hole without mentioning this important caveat.
Clarify in the subprocess documentation how searching for the executable to run works, noting that ``sys.executable`` is the recommended way to find the current interpreter.
* Add F_SETPIPE_SZ and F_GETPIPE_SZ to fcntl module
* Add pipesize parameter for subprocess.Popen class
This will allow the user to control the size of the pipes.
On linux the default is 64K. When a pipe is full it blocks for writing.
When a pipe is empty it blocks for reading. On processes that are
very fast this can lead to a lot of wasted CPU cycles. On a typical
Linux system the max pipe size is 1024K which is much better.
For high performance-oriented libraries such as xopen it is nice to
be able to set the pipe size.
The workaround without this feature is to use my_popen_process.stdout.fileno() in
conjuction with fcntl and 1031 (value of F_SETPIPE_SZ) to acquire this behavior.
On Unix, subprocess.Popen.send_signal() now polls the process status.
Polling reduces the risk of sending a signal to the wrong process if
the process completed, the Popen.returncode attribute is still None,
and the pid has been reassigned (recycled) to a new different
process.
* subprocess: Add user, group and extra_groups paremeters to subprocess.Popen
This adds a `user` parameter to the Popen constructor that will call
setreuid() in the child before calling exec(). This allows processes
running as root to safely drop privileges before running the subprocess
without having to use a preexec_fn.
This also adds a `group` parameter that will call setregid() in
the child process before calling exec().
Finally an `extra_groups` parameter was added that will call
setgroups() to set the supplimental groups.
Serhiy Storchaka
Gregory P. Smith
Joshua Herman
Guido van Rossum
Oleg Iarygin
Steve Dower
Stanley
richardhob
Bart Broere
Gregory P. Smith
Julien Palard
Christian Heimes
Ned Batchelder
Alex Waygood
Inada Naoki
Kumar Aditya
DonnaDia
Anthony Shaw
Jack DeVries
uniocto
andrei kulakov
Andre Delfino
sblondon
Ammar Askar
Paul Moore
Ruben Vorderman
Gareth Rees
Mathieu Dupuy
Zackery Spytz
Tim D. Smith
Victor Stinner
Jules Lasne (jlasne)
Patrick McLean
Tim Hoffmann
David Jones