Re: pkg/54192: lang/rust build error

[Kamil Rytarowski <n54%gmx.com@localhost>]

On 16.10.2019 17:25, Joerg Sonnenberger wrote:
>
>   So our per-process LWP identifier should behave like global identifier
>   from FreeBSD/Linux, because? They have little in common and the
existing
>   behavior is invalid even under the FreeBSD/Linux semantic.

This was just an example that thread id is not preserved across forks.

It's the same in NetBSD (but sometimes it can be by an accident preserved).


On 16.10.2019 17:29, Martin Husemann wrote:
> On Wed, Oct 16, 2019 at 05:14:56PM +0200, Joerg Sonnenberger wrote:
> > On a fundamental level, there are two sane models for a thread
> > identifier:
> > (1) It is globally unique.
> > (2) It is process local and invariant.
>
> Agreed so far, but the question is whether "invariant" holds across fork().

After fork(2) we have a new process entity and the LWP ID is local to
new thread.

> Pragmatically we should look for the easiest solution.

However... this behavior proposed by Joerg is still conformant with POSIX.

"A process shall be created with a single thread. If a multi-threaded
process calls fork(), the new process shall contain a replica of the
calling thread and its entire address space, possibly including the
states of mutexes and other resources. [...]
"

https://pubs.opengroup.org/onlinepubs/9699919799/functions/fork.html

So, let's go with it.

> Martin