From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/11081 Path: news.gmane.org!.POSTED!not-for-mail From: Szabolcs Nagy Newsgroups: gmane.linux.lib.musl.general Subject: Re: Reviving planned ldso changes Date: Sun, 26 Feb 2017 02:04:30 +0100 Message-ID: <20170226010429.GQ12395@port70.net> References: <20170103054351.GA8459@brightrain.aerifal.cx> <20170104060640.GM1555@brightrain.aerifal.cx> <20170104062203.GN1555@brightrain.aerifal.cx> <20170104193627.GO1555@brightrain.aerifal.cx> <587A988A.50105@Wilcox-Tech.com> <20170115174438.GD1533@brightrain.aerifal.cx> Reply-To: musl@lists.openwall.com NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: blaine.gmane.org 1488071085 4526 195.159.176.226 (26 Feb 2017 01:04:45 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sun, 26 Feb 2017 01:04:45 +0000 (UTC) User-Agent: Mutt/1.6.0 (2016-04-01) To: musl@lists.openwall.com Original-X-From: musl-return-11096-gllmg-musl=m.gmane.org@lists.openwall.com Sun Feb 26 02:04:41 2017 Return-path: Envelope-to: gllmg-musl@m.gmane.org Original-Received: from mother.openwall.net ([195.42.179.200]) by blaine.gmane.org with smtp (Exim 4.84_2) (envelope-from ) id 1chnGQ-0000IF-Gd for gllmg-musl@m.gmane.org; Sun, 26 Feb 2017 02:04:38 +0100 Original-Received: (qmail 9421 invoked by uid 550); 26 Feb 2017 01:04:42 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Original-Received: (qmail 9403 invoked from network); 26 Feb 2017 01:04:42 -0000 Mail-Followup-To: musl@lists.openwall.com Content-Disposition: inline In-Reply-To: <20170115174438.GD1533@brightrain.aerifal.cx> Xref: news.gmane.org gmane.linux.lib.musl.general:11081 Archived-At: * Rich Felker [2017-01-15 12:44:38 -0500]: > static void do_init_fini(struct dso *p) > { > size_t dyn[DYN_CNT]; > - int need_locking = libc.threads_minus_1; > - /* Allow recursive calls that arise when a library calls > - * dlopen from one of its constructors, but block any > - * other threads until all ctors have finished. */ > - if (need_locking) pthread_mutex_lock(&init_fini_lock); > - for (; p; p=p->prev) { > - if (p->constructed) continue; > + pthread_mutex_lock(&init_fini_lock); > + /* Construct in dependency order without any recursive state. */ > + while (p && !p->constructed) { > + /* The following loop descends into the first dependency > + * that is neither alredy constructed nor pending > + * construction due to circular deps, stopping only > + * when it reaches a dso with no remaining dependencies > + * to descend into. */ > + while (p->deps && p->deps[p->next_dep]) { > + if (!p->deps[p->next_dep]->constructed && > + !p->deps[p->next_dep]->next_dep) > + p = p->deps[p->next_dep++]; > + else > + p->next_dep++; > + } > p->constructed = 1; > decode_vec(p->dynv, dyn, DYN_CNT); > if (dyn[0] & ((1< @@ -1233,17 +1246,19 @@ static void do_init_fini(struct dso *p) > size_t *fn = laddr(p, dyn[DT_INIT_ARRAY]); > while (n--) ((void (*)(void))*fn++)(); > } > - if (!need_locking && libc.threads_minus_1) { > - need_locking = 1; > - pthread_mutex_lock(&init_fini_lock); > - } > - } > - if (need_locking) pthread_mutex_unlock(&init_fini_lock); > + /* Revisit "parent" dso which caused the just-constructed > + * dso to be pulled in as a dependency. On the next loop > + * iteration we will either descend to construct a sibling > + * of the just-constructed dso, or finish constructing the > + * parent if no unfinished deps remain. */ > + p = p->needed_by; > + } i think with a.deps: b c b.deps: c d b.needed_by: a c.needed_by: a the visiting order starting from a is a b c a and d never gets constructed. i was looking for the dfs stack (how you track back on the path you descended into the dependency tree), the needed_by entry might not point to the parent dso through which you arrived somewhere. i'm not sure what the right fix is, if needed_by is not used elsewhere then it could be set during traversal, but there might be other ways.