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 28409 invoked from network); 3 Apr 2020 09:29:11 -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; 3 Apr 2020 09:29:11 -0000 Received: (qmail 14321 invoked by uid 550); 3 Apr 2020 09:29:07 -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 14301 invoked from network); 3 Apr 2020 09:29:06 -0000 Date: Fri, 3 Apr 2020 11:28:54 +0200 From: Szabolcs Nagy To: musl@lists.openwall.com Cc: "zhangwentao (M)" Message-ID: <20200403092854.GY14278@port70.net> Mail-Followup-To: musl@lists.openwall.com, "zhangwentao (M)" References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Subject: Re: [musl] doubt about fork * guolongqiang [2020-04-03 06:37:44 +0000]: > Hello, > I have a problem about multi threads fork. The implement of fork not lock such as stdio file, > __thread_list_lock, or other global mutexs in musl libc before syscall of SYS_clone, this will > cause dead lock in child. Is this a bug? the standard is pretty clear that the child after fork in a multi-threaded process can only do async-signal-safe operations, anything that may lock is not as-safe. https://pubs.opengroup.org/onlinepubs/9699919799/functions/fork.html incidentally glibc tries to make certain operations work in the child by taking libc internal locks before fork and releasing them after, however that does not give strong guarantees of stdio use in the child because glibc supports malloc interposition and the interposed malloc can't reliably handle fork (i.e locks may be held in the child) so stdio (and all libc apis that may internally allocate) can still deadlock i.e. you don't get more guarantees on other implementations either than the standard. > > Hope your response! > --Guo Longqiang