Re: [PATCH 1/3] proc: Stop reporting eip and esp in /proc/PID/stat

From	Linus Torvalds <torvalds@linux-foundation.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH 1/3] proc: Stop reporting eip and esp in /proc/PID/stat
Date	2016-10-01 06:30 +0200
Message-ID	<snk5X-3oe-5@gated-at.bofh.it> (permalink)
References	<snagn-54E-9@gated-at.bofh.it> <snagn-54E-23@gated-at.bofh.it> <snbcl-5HB-17@gated-at.bofh.it> <snhUt-1Rg-5@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

On Fri, Sep 30, 2016 at 7:01 PM, Andy Lutomirski <luto@amacapital.net> 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

Thread

[PATCH 0/3] ABI CHANGE!!! Remove questionable remote SP reads Andy Lutomirski <luto@kernel.org> - 2016-09-30 20:00 +0200
  [PATCH 1/3] proc: Stop reporting eip and esp in /proc/PID/stat Andy Lutomirski <luto@kernel.org> - 2016-09-30 20:00 +0200
    Re: [PATCH 1/3] proc: Stop reporting eip and esp in /proc/PID/stat Jann Horn <jann@thejh.net> - 2016-09-30 21:00 +0200
      Re: [PATCH 1/3] proc: Stop reporting eip and esp in /proc/PID/stat Andy Lutomirski <luto@amacapital.net> - 2016-10-01 04:10 +0200
        Re: [PATCH 1/3] proc: Stop reporting eip and esp in /proc/PID/stat Linus Torvalds <torvalds@linux-foundation.org> - 2016-10-01 06:30 +0200
        Re: [PATCH 1/3] proc: Stop reporting eip and esp in /proc/PID/stat Jann Horn <jann@thejh.net> - 2016-10-01 12:40 +0200
  Re: [PATCH 0/3] ABI CHANGE!!! Remove questionable remote SP reads Andy Lutomirski <luto@amacapital.net> - 2016-10-04 01:10 +0200
    Re: [PATCH 0/3] ABI CHANGE!!! Remove questionable remote SP reads Linus Torvalds <torvalds@linux-foundation.org> - 2016-10-04 01:20 +0200
      Re: [PATCH 0/3] ABI CHANGE!!! Remove questionable remote SP reads Raymond Jennings <shentino@gmail.com> - 2016-10-04 09:10 +0200

csiph-web