From: Linus Torvalds <torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
To: Andy Lutomirski <luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org>
Cc: Jann Horn <jann-XZ1E9jl8jIdeoWH0uzbU5w@public.gmane.org>,
Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>,
Andy Lutomirski <luto-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
X86 ML <x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
"linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Brian Gerst <brgerst-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
Borislav Petkov <bp-Gina5bIWoIWzQB+pC5nmwQ@public.gmane.org>,
Linux API <linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Kees Cook <keescook-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>,
Tycho Andersen
<tycho.andersen-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org>,
Tetsuo Handa
<penguin-kernel-1yMVhJb1mP/7nzcFbJAaVXf5DAMn2ifp@public.gmane.org>
Subject: Re: [PATCH 1/3] proc: Stop reporting eip and esp in /proc/PID/stat
Date: Fri, 30 Sep 2016 21:22:08 -0700 [thread overview]
Message-ID: <CA+55aFxZkzC4uCXgL3BEGbbobtm0-n8FoNnswx5s=+8PNsGo2w@mail.gmail.com> (raw)
In-Reply-To: <CALCETrUBmsoUK5Shkjwo6n=BGaHFtZhhUZ=2uOcAzWUend-BXg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
On Fri, Sep 30, 2016 at 7:01 PM, Andy Lutomirski <luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org> wrote:
>
> Peter, how nasty would it be to add some lightish-weight lock that
> lets us pin a task in a non-running state? Maybe we could take the rq
> lock, do something to the task to make it sleepy (steal it off the
> queue?), unlock the lock, do whatever we're going, then take the lock
> again and put it back.
No. Don't do this. Forcing some sleeping lock in the core task state
/proc stuff is a nightmare. That thing ends up being used very heavily
under some loads. No _way_ is it ok to synchronize with the target
task.
> Or if we had a seqlock-like thing, we could maybe arrange for
> get_wchan to abort if the task get scheduled between when it starts
> and when it finishes.
seq_lock might be ok, but do we even need it? What's the worst that
can happen? An odd symbol name showing up in a race condition? Sounds
like a non-issue to me.
Linus
next prev parent reply other threads:[~2016-10-01 4:22 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-30 17:58 [PATCH 0/3] ABI CHANGE!!! Remove questionable remote SP reads Andy Lutomirski
2016-09-30 17:58 ` [PATCH 2/3] proc: Stop trying to report thread stacks Andy Lutomirski
2016-10-20 11:13 ` [tip:mm/urgent] fs/proc: " tip-bot for Andy Lutomirski
[not found] ` <cover.1475257877.git.luto-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2016-09-30 17:58 ` [PATCH 1/3] proc: Stop reporting eip and esp in /proc/PID/stat Andy Lutomirski
[not found] ` <a5fed4c3f4e33ed25d4bb03567e329bc5a712bcc.1475257877.git.luto-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2016-09-30 18:56 ` Jann Horn
[not found] ` <20160930185642.GH14666-J1fxOzX/cBvk1uMJSBkQmQ@public.gmane.org>
2016-10-01 2:01 ` Andy Lutomirski
[not found] ` <CALCETrUBmsoUK5Shkjwo6n=BGaHFtZhhUZ=2uOcAzWUend-BXg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2016-10-01 4:22 ` Linus Torvalds [this message]
2016-10-01 10:37 ` Jann Horn
[not found] ` <20161001103728.GM14666-J1fxOzX/cBvk1uMJSBkQmQ@public.gmane.org>
2016-10-14 18:25 ` Andy Lutomirski
2016-10-14 20:01 ` Tycho Andersen
2016-10-20 11:13 ` [tip:mm/urgent] fs/proc: " tip-bot for Andy Lutomirski
2016-11-01 14:36 ` [4.9-rc3] BUG: unable to handle kernel paging request at ffffc900144dfc60 Tetsuo Handa
2016-11-01 23:47 ` Linus Torvalds
2016-11-02 10:50 ` Tetsuo Handa
[not found] ` <201611021950.FEJ34368.HFFJOOMLtQOVSF-JPay3/Yim36HaxMnTkn67Xf5DAMn2ifp@public.gmane.org>
2016-11-02 14:05 ` Andy Lutomirski
2016-11-02 14:54 ` Linus Torvalds
2016-11-03 6:32 ` Ingo Molnar
2016-09-30 17:58 ` [PATCH 3/3] mm: Change vm_is_stack_for_task() to vm_is_stack_for_current() Andy Lutomirski
2016-10-20 11:14 ` [tip:mm/urgent] " tip-bot for Andy Lutomirski
2016-10-03 23:08 ` [PATCH 0/3] ABI CHANGE!!! Remove questionable remote SP reads Andy Lutomirski
[not found] ` <CALCETrULWhzph=kpbQUQSEkmsm6ZaRtp_bV9j5LFaFjLkawwMw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2016-10-03 23:17 ` Linus Torvalds
[not found] ` <CA+55aFzo0xpbxbajpgcfyYoLyKihCiyMfgc+yCJ+b9ohw6wycQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2016-10-04 7:06 ` Raymond Jennings
2016-10-14 18:26 ` Andy Lutomirski
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