Re: [PATCH v4 3.0-rc2-tip 13/22] 13: uprobes: Handing int3 and singlestep exception.

Peter Zijlstra
2011-06-16T12:36:05Z

On Thu, 2011-06-16 at 17:34 +0530, Srikar Dronamraju wrote:
> > > +
> > > +cleanup_ret:
> > > + if (u) {
> > > + down_read(&mm->mmap_sem);
> > > + if (!set_orig_insn(current, u, probept, true))
> >
> > we try to undo the probe? That doesn't make any sense. I thought you
> > meant to return to userspace, let it re-take the trap and try again
> > until you do manage to allocate the user resource.
>
> I meant removing the probe itself
> https://lkml.org/lkml/2011/4/21/279
>
> We could try reseting and retrying the trap. Just that we might end up
> looping under memory pressure.
>
> >
> > This behaviour makes probes totally unreliable under memory pressure.
>
> Under memory pressure we could be unreliable.

But that is total crap, there's nothing worse than unreliable debug
tools.