Re: [PATCH 3/3] pids: Make it possible to clone tasks with givenpids

[Oleg Nesterov]

On 11/11, Pavel Emelyanov wrote:
>
> First of all - let's imagine that we just want to clone a set of tasks. Then
> each of them will have to fork its kids, then report first of them that he's
> OK to fork and wait for it to report back, that forking is done. Then do the
> same for the rest of them. This is not impossible, but painful.

Why we should wait/report? They can do this in parallel, only
"set_last_pid + fork" needs the synchronization or "check + retry".

> Next - let's consider we have some tasks sharing various resources, e.g. mm-s
> or fd-tables. This means, that these tasks should be cloned in the carefully
> calculated sequence with CLONE_XXX flags set. In this case the described above
> scheme with fork() serialization simply won't work and we'll have to invent
> some fancy messaging with "now X fork with Y pid" and "X done with forking,
> please go on" messages.

Can't understand...

Oleg.

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