[crac] Integrated: PID adjustment on checkpoint

[Roman Marchenko]

On Tue, 20 Jun 2023 17:45:37 GMT, Roman Marchenko <rmarchenko at openjdk.org> wrote:

> On restore, there might be PID value conflicts because of small PID values, if it was checkpoint'ed in a container. Therefore, when checkpointing in a container, we need to move PID value for new processes to a particular value to avoid conflicts on restore.
> 
> See https://github.com/CRaC/example-lambda/blob/master/checkpoint.cmd.sh#L8 for example.
> 
> This PR contains implemented functionality similar to the example above, making this work out of the box. By default, if checkpointing, PID is adjusted only if Java's PID is 1 that means Java is run in a container. To adjust PID manually for a checkpoint'ed process, `-XX:CRaCMinPid=<value>` option should be used along with `CRaCCheckpointTo`. Min `CRaCMinPid` value is 1, max `CRaCMinPid` value is `UINT_MAX`, but it is actually limited by OS's pid_max.
> 
> There are the following possible scenarios for CRaC running in a container:
> 
>     // getpid   CRaCMinPid  |   set_last_pid      fork
>     // ------------------------------------------------
>     //   1         -        |    yes (default)    yes
>     //   1         1        |    no               yes
>     //   1        >1        |    yes              yes
>     //   >1        -        |    no               no
>     //   >1      <=getpid   |    no               no
>     //   >1       getpid<   |    yes              yes

This pull request has now been integrated.

Changeset: c48ccf51
Author:    Roman Marchenko <rmarchenko at openjdk.org>
Committer: Anton Kozlov <akozlov at openjdk.org>
URL:       https://git.openjdk.org/crac/commit/c48ccf5171a91461eaacba34a0f0d7af3a06b3c1
Stats:     332 lines in 6 files changed: 310 ins; 12 del; 10 mod

PID adjustment on checkpoint

Reviewed-by: akozlov

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PR: https://git.openjdk.org/crac/pull/86