From owner-freebsd-threads@freebsd.org Mon Feb 15 17:56:28 2016 Return-Path: Delivered-To: freebsd-threads@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id A5846AA8BAC for ; Mon, 15 Feb 2016 17:56:28 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from mailman.ysv.freebsd.org (mailman.ysv.freebsd.org [IPv6:2001:1900:2254:206a::50:5]) by mx1.freebsd.org (Postfix) with ESMTP id 8EF5D1781 for ; Mon, 15 Feb 2016 17:56:28 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: by mailman.ysv.freebsd.org (Postfix) id 8B99BAA8BAB; Mon, 15 Feb 2016 17:56:28 +0000 (UTC) Delivered-To: threads@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 8B0FDAA8BA8; Mon, 15 Feb 2016 17:56:28 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from kib.kiev.ua (kib.kiev.ua [IPv6:2001:470:d5e7:1::1]) (using TLSv1 with cipher DHE-RSA-CAMELLIA256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 0ACB3177E; Mon, 15 Feb 2016 17:56:27 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from tom.home (kostik@localhost [127.0.0.1]) by kib.kiev.ua (8.15.2/8.15.2) with ESMTPS id u1FHuMk4081577 (version=TLSv1 cipher=DHE-RSA-CAMELLIA256-SHA bits=256 verify=NO); Mon, 15 Feb 2016 19:56:22 +0200 (EET) (envelope-from kostikbel@gmail.com) DKIM-Filter: OpenDKIM Filter v2.10.3 kib.kiev.ua u1FHuMk4081577 Received: (from kostik@localhost) by tom.home (8.15.2/8.15.2/Submit) id u1FHuL2h081576; Mon, 15 Feb 2016 19:56:21 +0200 (EET) (envelope-from kostikbel@gmail.com) X-Authentication-Warning: tom.home: kostik set sender to kostikbel@gmail.com using -f Date: Mon, 15 Feb 2016 19:56:21 +0200 From: Konstantin Belousov To: Martin Simmons Cc: vangyzen@FreeBSD.org, threads@FreeBSD.org, arch@FreeBSD.org Subject: Re: libthr shared locks Message-ID: <20160215175621.GU91220@kib.kiev.ua> References: <20151223172528.GT3625@kib.kiev.ua> <56BE69B8.9020808@FreeBSD.org> <20160213143815.GB91220@kib.kiev.ua> <201602151417.u1FEHKwL003392@higson.cam.lispworks.com> <20160215144410.GT91220@kib.kiev.ua> <201602151735.u1FHZXKV006190@higson.cam.lispworks.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201602151735.u1FHZXKV006190@higson.cam.lispworks.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Spam-Status: No, score=-2.0 required=5.0 tests=ALL_TRUSTED,BAYES_00, DKIM_ADSP_CUSTOM_MED,FREEMAIL_FROM,NML_ADSP_CUSTOM_MED autolearn=no autolearn_force=no version=3.4.1 X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on tom.home X-BeenThere: freebsd-threads@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: Threading on FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 15 Feb 2016 17:56:28 -0000 On Mon, Feb 15, 2016 at 05:35:33PM +0000, Martin Simmons wrote: > >>>>> On Mon, 15 Feb 2016 16:44:10 +0200, Konstantin Belousov said: > > > > On Mon, Feb 15, 2016 at 02:17:20PM +0000, Martin Simmons wrote: > > > > > > Also, a general question: why not use some flag in the barrier (and other > > > objects) to indicate pshared, removing the need for __thr_pshared_offpage > > > except in init? > > > > But where would I keep the object ? All that I have with the current > > ABI is a single pointer, which de facto behaves like the flag which you > > proposed. It is either real pointer or (if set to some specific value > > impossible for a valid pointer) there is an offpage. > > I'm probably missing something, but I was thinking pthread_barrier_init would > do something like > > if ( attr is PTHREAD_PROCESS_PRIVATE ) { > bar = calloc(1, sizeof(struct pthread_barrier)); > pshared = 0; > } else { > bar = __thr_pshared_offpage(barrier, 1); > pshared = 1; > } > bar->psharedflag = pshared; > *barrier = bar; > > Then pthread_barrier_destroy would use the psharedflag slot to decide how to > free it and pthread_barrier_wait would need no changes. A process which has the page where the initialized pthread_barrier_t is located, must be able to operate on the barrier. Now, look at your scheme. One process which executed pthread_barrier_init(), performed what you proposed. What should do the pthread_barrier_wait() call in another process, which shares the 'barrier' with the first process, but does not share the whole address space ? After your pthread_barrier_init() executed, barrier contains the address of the object (off-page) in the other address space, for that process.