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Date:      Mon, 7 Apr 2014 14:06:12 +0500
From:      Jordan Hubbard <jkh@ixsystems.com>
To:        Warner Losh <imp@bsdimp.com>
Cc:        freebsd-arch <freebsd-arch@freebsd.org>
Subject:   Re: Compiler toolchain roadmap
Message-ID:  <8E22F8FA-CF71-4A47-BDE8-F3CE6158E1C9@ixsystems.com>
In-Reply-To: <9E11A6D4-9D18-422D-9514-4714AADDAEF4@gmail.com>
References:  <201404021607.s32G7mhw051355@svn.freebsd.org> <20140404115256.GA85137@ivaldir.etoilebsd.net> <F2A33EA8-14F2-4D62-9021-9023A1751E48@FreeBSD.org> <8D6AF193-A5A3-4A28-A230-97A543395ACA@ixsystems.com> <2E0EC8CB-B3EE-4DB8-A33D-58FD2107F14D@FreeBSD.org> <6A02504F-5543-4F91-92F6-7B4FB9A34DC4@ixsystems.com> <152D73EE-DF9E-4757-B547-F1F22B12C824@FreeBSD.org> <B06E1588-8828-485F-A407-3F19231F8EA5@ixsystems.com> <8E3BD3C1-A441-48C5-97BC-45EF67513096@FreeBSD.org> <6418BE83-BE78-473B-9311-C849507FA885@ixsystems.com> <CAJ-Vmom-19LujsTQ%2Bv4XozE%2BiEH18LMEQitBLC-At=DmsgkB%2BQ@mail.gmail.com> <EB9CE8A8-E897-4DE1-A8BC-80C6CC23E612@ixsystems.com> <9E11A6D4-9D18-422D-9514-4714AADDAEF4@gmail.com>

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On Apr 7, 2014, at 2:56 AM, Warner Losh <imp@bsdimp.com> wrote:

> First off, nobody every said we can=92t have nice things in the tree =
because of MIPS. Where was that said? It can=92t possibly be true =
because gcc supports blocks in the tree, so there=92s no impediment. =
LLVM-based things? Show me the money and bring one to the table and we =
can talk, but even then there=92s clang support for mips, so again =
that=92s not a big deal.

Perhaps I got lost somewhere along the way during the conversation =
thread with David Chisnall, but it sounded like we were both in favor of =
libdispatch and willing to at least grudgingly accept the proposition =
that we=92d never break the deadlock between having an absolute =
locked-in use case for it first vs having the fundamental technology =
available and in a position to change the way we do async programming =
(and perhaps get more dynamism into FreeBSD as a whole) when he said:

"I would certainly be in favour of importing it.  The package seems to =
be on every FreeBSD machine that I use, so I've become accustomed to =
having it there and just work.=94

Then he followed up with:

"The slight problem, however, is that we would still like to be able to =
build the base system with a more or less standard C compiler.  Blocks =
are in clang and are slowly making their way into commercial compilers, =
but the only two versions of gcc that support them are the ones shipped =
by Apple and FreeBSD.=94

and then:

"For embedded uses, we'd also like to build FreeBSD with =
vendor's-ugly-hacked-up-gcc-of-the-week.  This is less of an issue now =
for ARM, but MIPS vendors still hack up gcc in such a way that there's =
no way that they can get their changes upstreamed and then ship the =
result with their chips.=94

So what I took away from that was that my long and somewhat quixotic =
attempts to get libdispatch into FreeBSD (notionally scheduled for 8.1, =
then pushed out indefinitely) would probably remain quixotic due to a =
desire to keep base buildable by a fairly broad and non-freebsd =
controlled compiler toolchains in the case of MIPS.   Did I =
misunderstand something?  I=92d still love to get libdispatch into base =
such that other services can be layered on top of it.  There=92s a =
fundamental reason why we stuck it into Libsystem in OS X, and the =
notification system and other IPC technologies I'm hoping for as part of =
the =93services hub=94 work we=92ll be doing will all depend on =
libdispatch and blocks.

This is also, just in case anyone is wondering, far from academic.  =
Notification services are currently the bane of our existence over in =
FreeNAS, with services like Samba depending on a very buggy libinotify =
port for FreeBSD that we=92ve made some fixes to but ultimately just had =
to disable entirely (so Samba in FreeNAS will not support kernel =
notifications for awhile), it=92s that bad.  Just judging by the blatant =
nature of the bugs we=92ve found and fixed so far, it=92s also fairly =
clear that nobody has been using that port very much, or very =
intensively.

Unfortunately, the mobile computing space (to say nothing of the =
services space) needs to be a lot more aware of constant environmental =
changes (network links coming and going, time zones changing on the fly, =
service pairing relationships being created/broken, etc) and this takes =
a bit more architecture.  I=92m more than willing to help drive some of =
that architecture, too, but I sure don=92t want to do it on top of =
pthreads and raw socket I/O. :)

- Jordan




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