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=-3.3 required=5.0 tests=MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED,RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL,SPF_PASS autolearn=ham autolearn_force=no version=3.4.2 Received: (qmail 18196 invoked from network); 10 Apr 2020 01:03:11 -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 mother.openwall.net (195.42.179.200) by inbox.vuxu.org with UTF8ESMTPZ; 10 Apr 2020 01:03:11 -0000 Received: (qmail 1849 invoked by uid 550); 10 Apr 2020 01:03:08 -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 1820 invoked from network); 10 Apr 2020 01:03:07 -0000 Date: Thu, 9 Apr 2020 21:02:55 -0400 From: Rich Felker To: Florian Weimer Cc: musl@lists.openwall.com, Norbert Lange Message-ID: <20200410010255.GN11469@brightrain.aerifal.cx> References: <20200409181824.GD13749@port70.net> <87r1wwik8t.fsf@mid.deneb.enyo.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87r1wwik8t.fsf@mid.deneb.enyo.de> User-Agent: Mutt/1.5.21 (2010-09-15) Subject: Re: [musl] [BUG] sysconf implementing _SC_NPROCESSORS_(CONF|ONLN) incorrectly On Thu, Apr 09, 2020 at 08:31:30PM +0200, Florian Weimer wrote: > * Szabolcs Nagy: > > > * Norbert Lange [2020-04-09 12:29:20 +0200]: > >> Hello, > >> > >> I ran into a bug with trace-cmd when compiled against musl. > >> Turns out musl just returns the affinity mask in both cases. > >> > >> I know those functions are not standard, but the irony is that if they > >> are implemented, > >> then they prevent applications to use fallbacks. > >> > >> See the trace-cmd bugreport: > >> https://bugzilla.kernel.org/show_bug.cgi?id=206817 > > > > i think there are open unanswered questions about the right > > semantics it's not clear what user code may expect > > > > https://www.openwall.com/lists/musl/2019/03/16/1 > > https://www.openwall.com/lists/musl/2019/03/19/1 > > Stille, returning 1 if the sched_getaffinity system call fails > (because the affinity mask is unexpectedly large) will break some > software that assumes a true uniprocessor system if the processor > count is zero. (OpenJDK is an example.) > > This can also happen if there is some external affinity mask manager. > > For glibc, we had to change our logic to artificially inflate the CPU > to 2 if we cannot determine it, as the more conservative choice. Wait, you mean some software is abusing these interfaces to omit memory barriers or something? *facepalm* *sigh* Yes, we should probably do something better to implement these but I'm not sure what. Rich