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SubjectRe: futex question

* Peter Zijlstra <peterz@infradead.org> wrote:

> On Mon, 2009-10-05 at 13:59 +0200, Thomas Gleixner wrote:
>
> > Stared at the same place a minute ago :) But still I wonder if it's
> > a good idea to silently release locks and set the state to OWNERDEAD
> > instead of hitting the app programmer with a big clue stick in case
> > the app holds locks when calling execve().
>
> Agreed, I rather like the feedback. With regular exit like things
> there's just not much we can do to avoid the mess, but here we can
> actually avoid it, seems a waste not to do so.

Well, exec() has been a 'exit() + boot-strap next process' kind of thing
from the get go - with little state carried over into the new task. This
has security and robustness reasons as well.

So i think exec() should release all existing state, unless told
otherwise. Making it behave differently for robust futexes sounds
assymetric to me.

It might make sense though - a 'prevent exec because you are holding
locks!' thing. Dunno.

Cc:-ed a few execve() semantics experts who might want to chime in.

If a (buggy) app calls execve() with a (robust) futex still held should
we auto-force-release robust locks held, or fail the exec with an error
code? I think the forced release is a 'anomalous exit' thing mostly,
while calling exec() is not anomalous at all.

Ingo


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