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Re: ptrace improvement ideas (QPassSignals)


On 02/16, Oleg Nesterov wrote:
>
> On 02/16, Roland McGrath wrote:
>
> > It's already desireable to restructure
> > the ptrace implementation details so that ptrace-related storage is not
> > allocated when ptrace is not being used,
>
> Yes. IIRC, we already had the patches, but right now I can't recall
> if they were complete (most probably yes, except I am not sure about
> task->ptrace member). I'll try to find this series.

It turns out, it was complete but it should be changed a bit.

> Probably this is the first thing we should do.

Yes, I think this can help to implement the new features.

But there is a problem. If we want PTRACE_ATTCH_ALL_THREADS (and iiuc
we do want) we have to use GFP_ATOMIC to allocate ptrace_state under
tasklist_lock.

I wonder if we can invent a sleepable lock. Actually it is also needed
for cgroups, the guys from google are going to add the rw_semaphore into
signal_struct. But it depends on CONFIG_CGROUPS and doesn't cover exit.

Yes, yes, I am talking about implementation details again...

Oleg.


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