From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from dmta1006.nifty.com (mta-snd01007.nifty.com [106.153.227.39]) by sourceware.org (Postfix) with ESMTPS id 0CF7B3858D37 for ; Thu, 22 Jun 2023 23:49:46 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 0CF7B3858D37 Authentication-Results: sourceware.org; dmarc=fail (p=none dis=none) header.from=nifty.ne.jp Authentication-Results: sourceware.org; spf=fail smtp.mailfrom=nifty.ne.jp Received: from HP-Z230 by dmta1006.nifty.com with ESMTP id <20230622234944800.ZXWG.19085.HP-Z230@nifty.com>; Fri, 23 Jun 2023 08:49:44 +0900 Date: Fri, 23 Jun 2023 08:49:44 +0900 From: Takashi Yano To: cygwin@cygwin.com Subject: Re: Memory Barriers at pthread using CYGWIN Message-Id: <20230623084944.1022e7658a0e8c45c23d5ab7@nifty.ne.jp> In-Reply-To: References: <96718c68-af84-45a5-9332-337ec4b2f04a@email.android.com> <64831a27.170a0220.1f805.81bfSMTPIN_ADDED_BROKEN@mx.google.com> <1503743851.9556.1686370084334@aps7mgn-06> <20230620215300.def2e786b8fdce10b6317381@nifty.ne.jp> <20230622191959.a8ff48a0e1f1221c6de52a87@nifty.ne.jp> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.30; i686-pc-mingw32) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-11.0 required=5.0 tests=BAYES_00,GIT_PATCH_0,KAM_DMARC_STATUS,NICE_REPLY_A,SPF_HELO_PASS,SPF_PASS,TXREP,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On Thu, 22 Jun 2023 13:48:53 +0200 Corinna Vinschen wrote: > On Jun 22 19:19, Takashi Yano via Cygwin wrote: > > Any suggestions? > > > > On Tue, 20 Jun 2023 21:53:00 +0900 > > Takashi Yano wrote: > > > I looked into this problem, and I think this is a problem regarding > > > _my_tls initialization order, so far. This seems to happen in LDAP > > > environment. > > > > > > My assumption is: > > > > > > If the program is the first program which load cygwin1.dll, ldap > > > connection seems to be made before pthread::init_mainthread(). > > > In cyg_ldap.cc, cyg_ldap::connect(), cyg_ldap::search() or > > > cyg_ldap::next_page() calls cygwait() in which pthread::self() > > > is called. > > > > > > Then, _my_tls.tid is initialized with null_pthread, therefore, > > > _my_tls.tid is not set in pthread::init_mainthread(). > > > > > > This causes pthread_join() failure at: > > > winsup/cygwin/thread.cc: line 2196 > > > if (!is_good_object (&joiner)) > > > return EINVAL; > > > > > > > > > The first idea to fix this issue is remove set_tls_self_pointer() > > > call from pthread::self(). > > > > > > diff --git a/winsup/cygwin/thread.cc b/winsup/cygwin/thread.cc > > > index 5c1284a93..a0f2d5546 100644 > > > --- a/winsup/cygwin/thread.cc > > > +++ b/winsup/cygwin/thread.cc > > > @@ -392,10 +392,7 @@ pthread::self () > > > { > > > pthread *thread = _my_tls.tid; > > > if (!thread) > > > - { > > > - thread = pthread_null::get_null_pthread (); > > > - thread->set_tls_self_pointer (); > > > - } > > > + thread = pthread_null::get_null_pthread (); > > > return thread; > > > } > > > > > > > > > The secnd approach is to re-initialize _my_tls.tid in > > > pthread::init_mainthread() if _my_tls.tid is null_pthread. > > > > > > diff --git a/winsup/cygwin/thread.cc b/winsup/cygwin/thread.cc > > > index 5c1284a93..f614e01c4 100644 > > > --- a/winsup/cygwin/thread.cc > > > +++ b/winsup/cygwin/thread.cc > > > @@ -364,7 +364,7 @@ void > > > pthread::init_mainthread () > > > { > > > pthread *thread = _my_tls.tid; > > > - if (!thread) > > > + if (!thread || thread == pthread_null::get_null_pthread ()) > > > { > > > thread = new pthread (); > > > if (!thread) > > > > > > > > > Which is the better approach, do you think? > > > Or any other idea? > > The second approach looks good to me. There was a reason to call > set_tls_self_pointer from pthread::self, I guess. Resetting in > init_mainthread should have the least potential for side-effects. Thanks. I submitted the patch to cygwin-patches@cygwin.com. Please let me know if I can push it. -- Takashi Yano