From nobody Tue Jul 23 18:08:46 2024 X-Original-To: freebsd-arm@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4WT4sN16Wdz5SLcG; Tue, 23 Jul 2024 18:08:56 +0000 (UTC) (envelope-from kib@freebsd.org) Received: from kib.kiev.ua (kib.kiev.ua [IPv6:2001:470:d5e7:1::1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4WT4sM4RBvz4qjB; Tue, 23 Jul 2024 18:08:55 +0000 (UTC) (envelope-from kib@freebsd.org) Authentication-Results: mx1.freebsd.org; none Received: from tom.home (kib@localhost [127.0.0.1] (may be forged)) by kib.kiev.ua (8.18.1/8.18.1) with ESMTP id 46NI8k1o016912; Tue, 23 Jul 2024 21:08:49 +0300 (EEST) (envelope-from kib@freebsd.org) DKIM-Filter: OpenDKIM Filter v2.10.3 kib.kiev.ua 46NI8k1o016912 Received: (from kostik@localhost) by tom.home (8.18.1/8.18.1/Submit) id 46NI8kdU016911; Tue, 23 Jul 2024 21:08:46 +0300 (EEST) (envelope-from kib@freebsd.org) X-Authentication-Warning: tom.home: kostik set sender to kib@freebsd.org using -f Date: Tue, 23 Jul 2024 21:08:46 +0300 From: Konstantin Belousov To: mmel@freebsd.org Cc: FreeBSD Current , "freebsd-arm@freebsd.org" Subject: Re: armv7-on-aarch64 stuck at urdlck Message-ID: References: <86185657-e521-466b-89e2-f291aaac10a6@freebsd.org> <0EF18174-8735-46A4-BD71-FFA3472B319F@yahoo.com> <33251aa3-681f-4d17-afe9-953490afeaf0@gmail.com> <0DD19771-3AAB-469E-981B-1203F1C28233@yahoo.com> <6a969609-fa0e-419d-83d5-e4fcf0f6ec35@freebsd.org> List-Id: Porting FreeBSD to ARM processors List-Archive: https://lists.freebsd.org/archives/freebsd-arm List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-arm@FreeBSD.org MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6a969609-fa0e-419d-83d5-e4fcf0f6ec35@freebsd.org> X-Spam-Status: No, score=-2.9 required=5.0 tests=ALL_TRUSTED,BAYES_00 autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on tom.home X-Spamd-Bar: ---- X-Rspamd-Pre-Result: action=no action; module=replies; Message is reply to one we originated X-Spamd-Result: default: False [-4.00 / 15.00]; REPLY(-4.00)[]; ASN(0.00)[asn:6939, ipnet:2001:470::/32, country:US] X-Rspamd-Queue-Id: 4WT4sM4RBvz4qjB On Tue, Jul 23, 2024 at 07:46:51PM +0200, Michal Meloun wrote: > > > On 23.07.2024 11:36, Konstantin Belousov wrote: > > On Tue, Jul 23, 2024 at 09:53:41AM +0200, Michal Meloun wrote: > > > The good news is that I'm finally able to generate a working/locking > > > test case. The culprit (at least for me) is if "-mcpu" is used when > > > compiling libthr (e.g. indirectly injected via CPUTYPE in /etc/make.conf). > > > If it is not used, libthr is broken (regardless of -O level or debug/normal > > > build), but -mcpu=cortex-a15 will always produce a working libthr. > > > > I think this is very significant progress. > > > > Do you plan to drill down more to see what is going on? > > So the problem is now clear, and I fear it may apply to other architectures > as well. > dlopen_object() (from rtld_elf), > https://cgit.freebsd.org/src/tree/libexec/rtld-elf/rtld.c#n3766, > holds the rtld_bind_lock write lock for almost the entire time a new library > is loaded. > If the code uses a yet unresolved symbol to load the library, the rtl_bind() > function attempts to get read lock of rtld_bind_lock and a deadlock occurs. > > In this case, it round_up() in _thr_stack_fix_protection, > https://cgit.freebsd.org/src/tree/lib/libthr/thread/thr_stack.c#n136. > Issued by __aeabi_uidiv (since not all armv7 processors support HW divide). > > Unfortunately, I'm not sure how to fix it. The compiler can emit __aeabi_<> > in any place, and I'm not sure if it can resolve all the symbols used by > rtld_eld and libthr beforehand. This is a common issue, we pre-resolve a lot of symbols to avoid lock recursion. Please take a look at lib/libthr/thread/thr_rtld.c _thr_rtld_init().