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

On Fri, Sep 30, 2016 at 7:01 PM, Andy Lutomirski [off-list ref] 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