From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-2.0 required=5.0 tests=MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED,RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL,RDNS_NONE, SPF_PASS autolearn=ham autolearn_force=no version=3.4.2 Received: (qmail 16373 invoked from network); 10 Mar 2020 10:07:10 -0000 Received-SPF: pass (mother.openwall.net: domain of lists.openwall.com designates 195.42.179.200 as permitted sender) receiver=inbox.vuxu.org; client-ip=195.42.179.200 envelope-from= Received: from unknown (HELO mother.openwall.net) (195.42.179.200) by inbox.vuxu.org with ESMTP; 10 Mar 2020 10:07:10 -0000 Received: (qmail 17460 invoked by uid 550); 10 Mar 2020 10:07:09 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Reply-To: musl@lists.openwall.com Received: (qmail 17442 invoked from network); 10 Mar 2020 10:07:08 -0000 Date: Tue, 10 Mar 2020 11:06:57 +0100 From: Szabolcs Nagy To: Pirmin Walthert Cc: musl@lists.openwall.com Message-ID: <20200310100657.GK14278@port70.net> Mail-Followup-To: Pirmin Walthert , musl@lists.openwall.com References: <41ea935d-39e4-1460-e502-5c82d7dd6a4d@wwcom.ch> <20200309171227.GY11469@brightrain.aerifal.cx> <82b69741-72e6-ab53-c523-ce4e1e7dc98e@wwcom.ch> <20200309185536.GI14278@port70.net> <5957e47c-50c6-0ae1-3e5c-32fd96c756eb@wwcom.ch> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5957e47c-50c6-0ae1-3e5c-32fd96c756eb@wwcom.ch> User-Agent: Mutt/1.10.1 (2018-07-13) Subject: Re: [musl] Re: FYI: some observations when testing next-gen malloc * Pirmin Walthert [2020-03-10 10:44:46 +0100]: > Am 09.03.20 um 19:55 schrieb Szabolcs Nagy: > > * Pirmin Walthert [2020-03-09 19:14:59 +0100]: > > > Am 09.03.20 um 18:12 schrieb Rich Felker: > > > > It's not described very rigorously, but effectively it's in an async > > > > signal context and can only call functions which are AS-safe. > > > > > > > > A future version of the standard is expected to drop the requirement > > > > that fork itself be async-signal-safe, and may thereby add > > > > requirements to synchronize against some or all internal locks so that > > > > the child can inherit a working context. But the right solution here is > > > > always to stop using fork without exec. > > > > > > > > Rich > > > Well, I have now changed the code a bit to make sure that no > > > async-signal-unsafe command is being executed before execl. Things I've > > > removed: > > > > > > a call to cap_from_text, cap_set_proc and cap_free has been removed as well > > > as sched_setscheduler. Now the only thing being executed before execl in the > > > child process is closefrom() > > > > closefrom is not as-safe. > > > > i think it reads /proc/self/fd directory to close fds. > > (haven't checked the specific asterisk version) > > opendir calls malloc so it can deadlock. > > > Indeed I am not able to reproduce the problem any longer with a modified > version of asterisk. What I've changed is: > > Removed some code that sets the capabilities after fork() (with > cap_from_text, cap_set_proc, cap_free) and closefrom replaced with a thumb > loop over all possible fds up to sysconf(_SC_OPEN_MAX). With this > modification the fd closing procedure with max open files set to 21471 now > needs 7ms instead of 70ns (so a slowdown by times 100), however this is not > critical in our environment... > > Will discuss the findings with the asterisk developers. > > Thanks for your hints! good. ideally they would use close-on-exec fds and then you don't need such ugliness. please don't drop the list from replies.