Re: [RFD] posix-timers: CRIU woes

Pavel Tikhomirov
2023-05-11T09:53:39Z

On 11.05.2023 17:36, Thomas Gleixner wrote:
> On Thu, May 11 2023 at 11:17, Pavel Tikhomirov wrote:
>> On 10.05.2023 16:16, Andrey Vagin wrote:
>>>>
>>>> So because of that half thought out user space ABI we are now up the
>>>> regression creek without a paddle, unless CRIU can accomodate to a
>>>> different restore mechanism to lift this restriction from the kernel.
>>>>
>>> If you give us a new API to create timers with specified id-s, we will
>>> figure out how to live with it. It isn't good to ask users to update
>>> CRIU to work on new kernels, but here are reasons and event improvements
>>> for CRIU, so I think it's worth it.
>>
>> I agree, any API to create timers with specified id-s would work for new
>> CRIU versions.
>
> The real question is whether this will cause any upheaval when a new
> kernel meets a non-updated CRIU stack.

Creation of posix timer would hang forever in this loop
https://github.com/checkpoint-restore/criu/blob/33dd66c6fc93c47213aaa0447a94d97ba1fa56ba/criu/pie/restorer.c#L1185
if old criu is run on new kernel (without consecutive id allocation) AFAICS.

> You know the UABI regression rules of the kernel...
>
> Thanks,
>
> tglx
>

--
Best regards, Tikhomirov Pavel
Senior Software Developer, Virtuozzo.