From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/9519 Path: news.gmane.org!not-for-mail From: Felix Fietkau Newsgroups: gmane.linux.lib.musl.general Subject: Re: FreeBSD's Google Summer of Code 2016 Date: Mon, 7 Mar 2016 09:32:17 +0100 Message-ID: <56DD3C91.2070403@openwrt.org> References: <56DB3D70.8010601@FreeBSD.org> <20160305212517.GK9349@brightrain.aerifal.cx> <56DB6095.4060204@FreeBSD.org> <20160305233254.GL9349@brightrain.aerifal.cx> <56DB766A.3050500@FreeBSD.org> <20160306002547.GM9349@brightrain.aerifal.cx> Reply-To: musl@lists.openwall.com NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Trace: ger.gmane.org 1457339556 25301 80.91.229.3 (7 Mar 2016 08:32:36 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 7 Mar 2016 08:32:36 +0000 (UTC) To: musl@lists.openwall.com, Pedro Giffuni Original-X-From: musl-return-9532-gllmg-musl=m.gmane.org@lists.openwall.com Mon Mar 07 09:32:35 2016 Return-path: Envelope-to: gllmg-musl@m.gmane.org Original-Received: from mother.openwall.net ([195.42.179.200]) by plane.gmane.org with smtp (Exim 4.69) (envelope-from ) id 1acqaf-0002MV-Jf for gllmg-musl@m.gmane.org; Mon, 07 Mar 2016 09:32:33 +0100 Original-Received: (qmail 3710 invoked by uid 550); 7 Mar 2016 08:32:30 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Original-Received: (qmail 3691 invoked from network); 7 Mar 2016 08:32:30 -0000 X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on arrakis.dune.hu X-Spam-Level: X-Spam-Status: No, score=-1.0 required=5.0 tests=ALL_TRUSTED autolearn=ham autolearn_force=no version=3.4.1 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 In-Reply-To: <20160306002547.GM9349@brightrain.aerifal.cx> Xref: news.gmane.org gmane.linux.lib.musl.general:9519 Archived-At: On 2016-03-06 01:25, Rich Felker wrote: > On Sat, Mar 05, 2016 at 07:14:34PM -0500, Pedro Giffuni wrote: >> >> >> On 03/05/16 18:32, Rich Felker wrote: >> >On Sat, Mar 05, 2016 at 05:41:25PM -0500, Pedro Giffuni wrote: >> >>First of all, great to hear there is interest on the musl side too. >> >> >> >>I think the biggest precedent of porting linux-oriented C libraries >> >>came from Debian's kFreeBSD. We accomodated a little by for them >> >>by defining __FreeBSD_kernel__ in sys/param.h. >> >> >> >>While using the optional linux-abi futex in FreeBSD could be an option, >> >>it is not really the cleanest option. The Debian guys did a port of >> >>NPTL using regular pthreads: >> >> >> >> Of course I ahould have meant "based on regular FreeBSD kernel services". >> >> >>http://thread.gmane.org/gmane.linux.debian.ports.bsd/11702 >> >> >> >>I am certain this will require more research but it would be useful >> >>for other ports as well. >> > >> >> We could ask Petr Salinger for the details, but I am pretty sure >> FreeBSD has the required functionality natively. >> >> >Glibc/NPTL has a lot of what I'd call "gratuitous abstraction" (like >> >the lll stuff) in their pthread primitives which makes this >> >"possible". I call it gratuitous because it's really really hard to >> >achieve correct implementations of the pthread sync primitives that >> >don't have serious corner-case bugs, and it's unlikely that their >> >abstractions actually suffice to make correct alternate >> >implementations. >> > >> >musl does not have any such abstraction. We require a compare-and-swap >> >operation or equivalent on which arbitrary atomic operations can be >> >constructed, a futex or equivalent operation that's roughly >> >while(*addr==expected) sleep(), and implement all the sync primitives >> >just once on top of these. >> > >> >> I am not a threading expert (or even a CS guy), but it sounds like >> mutex(9) with condvar(9) would do [1]: > > No, they don't satisfy the needs of musl; they have their own > additional storage requirements and are probably not AS-safe. It might > be possible to use them to implement a userspace-emulated futex queue > (only if they are AS-safe), but I don't see a way to extend that to > the process-shared case. What about umtx? It's supposed to be just like linux futex. - Felix