Re: RFC: on adding new CLONE_* flags [WAS Re: [PATCH 0/4] clone: add CLONE_PIDFD]

[Florian Weimer]

* Linus Torvalds:

> On Mon, Apr 29, 2019 at 12:55 PM Jann Horn <jannh@xxxxxxxxxx> wrote:
>>
>> ... I guess that already has a name, and it's called vfork(). (Well,
>> except that the Linux vfork() isn't a real vfork().)
>
> What?
>
> Linux vfork() is very much a real vfork(). What do you mean?

In Linux-as-the-ABI (as opposed to Linux-as-the-implementation), vfork
is sometimes implemented as fork, so applications cannot rely on the
vfork behavior regarding the stopped parent and the shared address
space.

In fact, it would be nice to have a flag we can check in the posix_spawn
implementation, so that we can support vfork-as-fork without any run
time cost to native Linux.

Thanks,
Florian