From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 25159 invoked by alias); 12 Jun 2018 13:11:44 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Received: (qmail 23839 invoked by uid 89); 12 Jun 2018 13:11:43 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-6.7 required=5.0 tests=AWL,BAYES_00,GIT_PATCH_2,SPF_HELO_PASS autolearn=ham version=3.3.2 spammy=Its X-HELO: mx1.redhat.com Subject: Re: Restartable Sequences system call merged into Linux To: Mathieu Desnoyers Cc: Carlos O'Donell , Peter Zijlstra , "Paul E. McKenney" , Boqun Feng , Thomas Gleixner , linux-kernel , libc-alpha References: <1084280721.10859.1528746558696.JavaMail.zimbra@efficios.com> <31fc101a-295b-067b-1a82-7e9e509fc92f@redhat.com> <305409897.10888.1528747473727.JavaMail.zimbra@efficios.com> From: Florian Weimer Message-ID: <091061df-3482-8762-30e4-feaf3417be11@redhat.com> Date: Tue, 12 Jun 2018 13:11:00 -0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: <305409897.10888.1528747473727.JavaMail.zimbra@efficios.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-SW-Source: 2018-06/txt/msg00239.txt.bz2 On 06/11/2018 10:04 PM, Mathieu Desnoyers wrote: > ----- On Jun 11, 2018, at 3:55 PM, Florian Weimer fweimer@redhat.com wrote: > >> On 06/11/2018 09:49 PM, Mathieu Desnoyers wrote: >>> It should be noted that there can be only one rseq TLS area registered per >>> thread, >>> which can then be used by many libraries and by the executable, so this is a >>> process-wide (per-thread) resource that we need to manage carefully. >> >> Is it possible to resize the area after thread creation, perhaps even >> from other threads? > > I'm not sure why we would want to resize it. The per-thread area is fixed-size. > Its layout is here: include/uapi/linux/rseq.h: struct rseq Looks I was mistaken and this is very similar to the robust mutex list. Should we treat it the same way? Always allocate it for each new thread and register it with the kernel? > The ABI is designed so that all users (program and libraries) can interact > through this per-thread TLS area. Then the user code needs just the address of the structure. How much coordination is needed between different users of this interface? Looking at the the section hacks, I don't think we want to put this into glibc at this stage. It looks more like something for which we traditionally require compiler support. Thanks, Florian