Re: [PATCH] Remove bogus WARN_ON in futex_wait

Daniel Jacobowitz
2004-05-19T14:44:14Z

On Wed, May 19, 2004 at 12:50:01PM +0200, Andi Kleen wrote:
> On Wed, 19 May 2004 13:43:40 +0300
> Muli Ben-Yehuda <mulix@mulix.org> wrote:
>
> > On Wed, May 19, 2004 at 12:23:50PM +0200, Andi Kleen wrote:
> > >
> > > futex_wait goes to an interruptible sleep, but does a WARN_ON later
> > > if it wakes up early. But waking up early is totally legal, since
> > > the sleep is interruptible and any signal can wake it up.
> >
> > That's not what the WARN_ON is saynig, unless I'm missing
> > something. It's checking if we were woken up early and there's no
> > signal pending for us.
>
> True. Anyways, it seems to happen in practice.

I'm guessing that at least one of the ways to trigger this is with
ptrace. Linux has a nasty habit of waking "wake on signal" sleeps
without a signal if ptrace cancels the signal.

--
Daniel Jacobowitz