Re: FreeBSD's Google Summer of Code 2016

[Pedro Giffuni <pfg@FreeBSD.org>]

Hello;

On 03/07/16 08:06, Szabolcs Nagy wrote:
> * Felix Fietkau <nbd@openwrt.org> [2016-03-07 09:32:17 +0100]:
>> What about umtx? It's supposed to be just like linux futex.
>>
>
> i see
> https://svnweb.FreeBSD.org/base/head/sys/sys/umtx.h?view=markup
>
> but there seems to be no documentation for it in
> https://www.freebsd.org/cgi/man.cgi
>
> if _umtx_op does what it seems to do, then i think musl can be
> ported to native freebsd syscalls, but i don't know how much
> syscall abi stability freebsd is willing to guarantee.
> i think historically that was assumed to be a private interface
> between the libc and the kernel on bsd (in which case a musl port
> cannot be easily maintained outside of the bsd source repo).
>

I wouldn't worry about ABI stability. We are not allowed to break
the ABI per branch and with so many users depending on being able
to run previous versions of FreeBSD within jails, and with the
native threads and now linux binaries depending on it, there is
no chance we can break it,

We may introduce a new interface in the future (who knows) but we
can't just drop an old one.

Pedro.