From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.io/gmane.linux.lib.musl.general/22181 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Rich Felker Newsgroups: gmane.linux.lib.musl.general Subject: Re: [PATCH] __libc_exit_fini forgets to do pthread_mutex_unlock Date: Wed, 2 Jul 2025 10:33:21 -0400 Message-ID: <20250702143321.GI1827@brightrain.aerifal.cx> References: <20250702022854.30301-1-rebecca.zhang.cn@windriver.com> Reply-To: musl@lists.openwall.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="35520"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Mutt/1.9.5 (2018-04-13) Cc: musl@lists.openwall.com, rebecca.zhang.cn@windriver.com, wenbin.deng.cn@windriver.com To: Markus Wichmann Original-X-From: musl-return-22201-gllmg-musl=m.gmane-mx.org@lists.openwall.com Wed Jul 02 16:33:40 2025 Return-path: Envelope-to: gllmg-musl@m.gmane-mx.org Original-Received: from second.openwall.net ([193.110.157.125]) by ciao.gmane.io with smtp (Exim 4.92) (envelope-from ) id 1uWyWq-00095h-PX for gllmg-musl@m.gmane-mx.org; Wed, 02 Jul 2025 16:33:40 +0200 Original-Received: (qmail 25724 invoked by uid 550); 2 Jul 2025 14:33:31 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: x-ms-reactions: disallow Original-Received: (qmail 25688 invoked from network); 2 Jul 2025 14:33:31 -0000 Content-Disposition: inline In-Reply-To: Xref: news.gmane.io gmane.linux.lib.musl.general:22181 Archived-At: On Wed, Jul 02, 2025 at 06:30:33AM +0200, Markus Wichmann wrote: > Am Wed, Jul 02, 2025 at 10:28:54AM +0800 schrieb rebecca.zhang.cn@windriver.com: > > From: Rebecca Zhang > > > > This commit fixes the issue that __libc_exit_fini only do > > pthread_mutex_lock, but forget to do pthread_mutex_unlock. > > --- > > ldso/dynlink.c | 1 + > > 1 file changed, 1 insertion(+) > > > > diff --git a/ldso/dynlink.c b/ldso/dynlink.c > > index ceca3c9..7885675 100644 > > --- a/ldso/dynlink.c > > +++ b/ldso/dynlink.c > > @@ -1492,6 +1492,7 @@ void __libc_exit_fini() > > fpaddr(p, dyn[DT_FINI])(); > > #endif > > } > > + pthread_mutex_unlock(&init_fini_lock); > > } > > > > void __ldso_atfork(int who) > > -- > > 2.34.1 > > > I think that is a deliberate omision. __libc_exit_fini() is called on > process exit. After it runs, it must not run again, and no new > initializer must run at all. The process will exit very soon anyway. The > only way to deadlock here is if a destructor calls exit(), which they > aren't allowed to do. It is very much deliberate that this lock is never released. Similarly with a number of other locks they did not seem to notice that would cause the same behavior even if this one was changed. The general pattern is "a contractual requirement of exit is that all things of category X have finished before the process terminates", and this necessitates ensuring that no new "things of category X" can come into existence once you're past the step where they're processed. Other examples include flushing stdio (must not allow any new data to become buffered after flush is complete) and processing atexit handlers (must not allow a new handler to be registered after the loop that runs them). Rich