Re: [RFC PATCH] posix timers: allocate timer id per task

[Stanislav Kinsbursky]

15.10.2012 21:04, Peter Zijlstra ÐÐÑÐÑ:
> On Mon, 2012-10-15 at 20:17 +0400, Stanislav Kinsbursky wrote:
> > This patch is required CRIU project (www.criu.org).
> > To migrate processes with posix timers we have to make sure, that we can
> > restore posix timer with proper id.
> > Currently, this is not true, because timer ids are allocated globally.
> > So, this is precursor patch and it's purpose is make posix timer id to be
> > allocated per task.
> >
> > Patch replaces global idr with global hash table for posix timers and
> > makes timer ids unique not globally, but per task. Next free timer id is type
> > of integer and stored on signal struct (posix_timer_id). If free timer id
> > reaches negative value on timer creation, it will be dropped to zero and
> > -EAGAIN will be returned to user.
> > Hash table is size of page (4KB).
> > Key is constructed as follows:
> > key = hash_ptr(current->signal) ^ hash_32(posix_timer_id);
>
> but but but.. isn't this what namespaces were invented for to solve? Why
> not use the regular namespace infrastructure?

The reason is that CRIU have to support single processes within existent namespaces.

--
Best regards,
Stanislav Kinsbursky
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