From: ebiederm@xmission.com (Eric W. Biederman)
To: Aleksa Sarai <cyphar@cyphar.com>
Cc: linux-kernel@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>,
Kees Cook <keescook@chromium.org>, Pavel Machek <pavel@ucw.cz>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
linux-fsdevel@vger.kernel.org, Oleg Nesterov <oleg@redhat.com>,
linux-pm@vger.kernel.org
Subject: Re: [RFC][PATCH] exec: Freeze the other threads during a multi-threaded exec
Date: Tue, 28 Jul 2020 07:18:37 -0500 [thread overview]
Message-ID: <87bljzkf36.fsf@x220.int.ebiederm.org> (raw)
In-Reply-To: <20200728092359.jrv7ygt6dwktwsgp@yavin.dot.cyphar.com> (Aleksa Sarai's message of "Tue, 28 Jul 2020 19:41:09 +1000")
Aleksa Sarai <cyphar@cyphar.com> writes:
> On 2020-07-27, Eric W. Biederman <ebiederm@xmission.com> wrote:
>> To the best of my knowledge processes with more than one thread
>> calling exec are not common, and as all of the threads will be killed
>> by exec there does not appear to be any useful work a thread can
>> reliably do during exec.
>
> Every Go program which calls exec (this includes runc, Docker, LXD,
> Kubernetes, et al) fills the niche of "multi-threaded program that calls
> exec" -- all Go programs are multi-threaded and there's no way of
> disabling this. This will most likely cause pretty bad performance
> regression for basically all container workloads.
So it is a good point that container runtimes use Go, and that
fundamentally anything that uses Go will be multi-threaded. Having just
looked closely at this I don't think in practice this is an issue even
at this early state of my code.
If those other threads are sleeping the code I have implemented should
be a no-op.
If those threads aren't sleeping you have undefined behavior, as at
some point the kernel will come through and kill those threads.
Further unless I am completely mistaken the container runtimes use
forkAndExecInChild from go/src/syscall/exec_linux.go which performs a
vfork before performing the exec.
Eric
prev parent reply other threads:[~2020-07-28 12:21 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-27 21:03 [RFC][PATCH] exec: Freeze the other threads during a multi-threaded exec Eric W. Biederman
2020-07-28 0:20 ` Linus Torvalds
2020-07-28 12:39 ` Eric W. Biederman
2020-07-28 13:20 ` Eric W. Biederman
2020-07-28 18:17 ` Linus Torvalds
2020-07-30 13:16 ` Eric W. Biederman
2020-07-30 22:56 ` [RFC][PATCH] exec: Conceal the other threads from wakeups during exec Eric W. Biederman
2020-07-30 23:17 ` Linus Torvalds
2020-07-31 17:16 ` Eric W. Biederman
2020-07-31 17:41 ` Linus Torvalds
2020-07-31 20:07 ` Eric W. Biederman
2020-07-31 6:28 ` Oleg Nesterov
2020-07-31 16:50 ` Eric W. Biederman
2020-07-28 9:41 ` [RFC][PATCH] exec: Freeze the other threads during a multi-threaded exec Aleksa Sarai
2020-07-28 12:18 ` Eric W. Biederman [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87bljzkf36.fsf@x220.int.ebiederm.org \
--to=ebiederm@xmission.com \
--cc=cyphar@cyphar.com \
--cc=keescook@chromium.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pm@vger.kernel.org \
--cc=oleg@redhat.com \
--cc=pavel@ucw.cz \
--cc=rjw@rjwysocki.net \
--cc=torvalds@linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).