From: Linus Torvalds <torvalds@linux-foundation.org>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Kees Cook <keescook@chromium.org>, Pavel Machek <pavel@ucw.cz>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Oleg Nesterov <oleg@redhat.com>,
Linux PM <linux-pm@vger.kernel.org>
Subject: Re: [RFC][PATCH] exec: Freeze the other threads during a multi-threaded exec
Date: Tue, 28 Jul 2020 11:17:02 -0700 [thread overview]
Message-ID: <CAHk-=wj+ynePRJC3U5Tjn+ZBRAE3y7=anc=zFhL=ycxyKP8BxA@mail.gmail.com> (raw)
In-Reply-To: <87h7trg4ie.fsf@x220.int.ebiederm.org>
On Tue, Jul 28, 2020 at 6:23 AM Eric W. Biederman <ebiederm@xmission.com> wrote:
>
> For exec all I care about are user space threads. So it appears the
> freezer infrastructure adds very little.
Yeah. 99% of the freezer stuff is for just adding the magic notations
for kernel threads, and for any user space threads it seems the wrong
interface.
> Now to see if I can find another way to divert a task into a slow path
> as it wakes up, so I don't need to manually wrap all of the sleeping
> calls. Something that plays nice with the scheduler.
The thing is, how many places really care?
Because I think there are like five of them. And they are all marked
by taking cred_guard_mutex, or the file table lock.
So it seems really excessive to then create some whole new "let's
serialize every thread", when you actually don't care about any of it,
except for a couple of very very special cases.
If you care about "thread count stable", you care about exit() and
clone(). You don't care about threads that are happily running - or
sleeping - doing their own thing.
So trying to catch those threads and freezing them really feels like
entirely the wrong interface.
Linus
next prev parent reply other threads:[~2020-07-28 18:17 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 [this message]
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
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