From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: ludo@gnu.org (Ludovic =?UTF-8?Q?Court=C3=A8s?=) Newsgroups: gmane.lisp.guile.bugs Subject: bug#31878: Module autoloading is not thread safe Date: Thu, 23 Aug 2018 15:54:00 +0200 Message-ID: <87va81p4sn.fsf@gnu.org> References: <87k1qwwhu2.fsf@gnu.org> <878t7cwdqu.fsf@gnu.org> <87h8m0uw3z.fsf@gnu.org> <878t4xdfag.fsf@netris.org> <87woshbzak.fsf@netris.org> NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Trace: blaine.gmane.org 1535034352 4655 195.159.176.226 (23 Aug 2018 14:25:52 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Thu, 23 Aug 2018 14:25:52 +0000 (UTC) User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) Cc: 31878@debbugs.gnu.org To: Mark H Weaver Original-X-From: bug-guile-bounces+guile-bugs=m.gmane.org@gnu.org Thu Aug 23 16:25:48 2018 Return-path: Envelope-to: guile-bugs@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1fsqYV-00014s-K5 for guile-bugs@m.gmane.org; Thu, 23 Aug 2018 16:25:47 +0200 Original-Received: from localhost ([::1]:36834 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fsqac-0005ls-0P for guile-bugs@m.gmane.org; Thu, 23 Aug 2018 10:27:58 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:52208) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fsq4p-0006iL-VY for bug-guile@gnu.org; Thu, 23 Aug 2018 09:55:13 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fsq4m-0008Pg-MU for bug-guile@gnu.org; Thu, 23 Aug 2018 09:55:07 -0400 Original-Received: from debbugs.gnu.org ([208.118.235.43]:53361) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1fsq4m-0008PZ-F1 for bug-guile@gnu.org; Thu, 23 Aug 2018 09:55:04 -0400 Original-Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.84_2) (envelope-from ) id 1fsq4k-0004or-EQ; Thu, 23 Aug 2018 09:55:04 -0400 X-Loop: help-debbugs@gnu.org Resent-From: ludo@gnu.org (Ludovic =?UTF-8?Q?Court=C3=A8s?=) Original-Sender: "Debbugs-submit" Resent-CC: bug-guile@gnu.org Resent-Date: Thu, 23 Aug 2018 13:55:02 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: followup 31878 X-GNU-PR-Package: guile X-GNU-PR-Keywords: Original-Received: via spool by 31878-submit@debbugs.gnu.org id=B31878.153503245418460 (code B ref 31878); Thu, 23 Aug 2018 13:55:02 +0000 Original-Received: (at 31878) by debbugs.gnu.org; 23 Aug 2018 13:54:14 +0000 Original-Received: from localhost ([127.0.0.1]:58379 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1fsq3y-0004ng-G8 for submit@debbugs.gnu.org; Thu, 23 Aug 2018 09:54:14 -0400 Original-Received: from eggs.gnu.org ([208.118.235.92]:59123) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1fsq3w-0004nO-H6 for 31878@debbugs.gnu.org; Thu, 23 Aug 2018 09:54:12 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fsq3l-0007jU-St for 31878@debbugs.gnu.org; Thu, 23 Aug 2018 09:54:07 -0400 Original-Received: from fencepost.gnu.org ([2001:4830:134:3::e]:34028) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fsq3l-0007jE-O4; Thu, 23 Aug 2018 09:54:01 -0400 Original-Received: from [193.50.110.186] (port=39684 helo=ribbon) by fencepost.gnu.org with esmtpsa (TLS1.2:RSA_AES_256_CBC_SHA1:256) (Exim 4.82) (envelope-from ) id 1fsq3l-0000pJ-FG; Thu, 23 Aug 2018 09:54:01 -0400 X-URL: http://www.fdn.fr/~lcourtes/ X-Revolutionary-Date: 6 Fructidor an 226 de la =?UTF-8?Q?R=C3=A9volution?= X-PGP-Key-ID: 0x090B11993D9AEBB5 X-PGP-Key: http://www.fdn.fr/~lcourtes/ludovic.asc X-PGP-Fingerprint: 3CE4 6455 8A84 FDC6 9DB4 0CFB 090B 1199 3D9A EBB5 X-OS: x86_64-pc-linux-gnu In-Reply-To: <87woshbzak.fsf@netris.org> (Mark H. Weaver's message of "Wed, 22 Aug 2018 22:18:59 -0400") X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 208.118.235.43 X-BeenThere: bug-guile@gnu.org List-Id: "Bug reports for GUILE, GNU's Ubiquitous Extension Language" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: bug-guile-bounces+guile-bugs=m.gmane.org@gnu.org Original-Sender: "bug-guile" Xref: news.gmane.org gmane.lisp.guile.bugs:9129 Archived-At: Mark H Weaver skribis: > I forgot to mention an important aspect of the proposed auto-load > locking here. It would not be a global lock, but rather a lock specific > to the module being loaded. So, I guess we would need a global table of > locks for modules-being-loaded. Right (we can=E2=80=99t add a mutex to the module record without breaking t= he ABI.) > Since Guile (unfortunately) allows cyclic module dependencies, we would > need a mechanism to avoid deadlocks in case modules A and B both import > each other, and two threads concurrently attempt to load those modules. > > The first idea that comes to mind is to also have a global structure > storing a partial order on the modules currently being loaded. If, > while module A is being loaded, there's an attempt to auto-load module > B, then an entry (A < B) would added to the partial order. The partial > order would not allow cycles to be introduced, reporting an error in > that case. In case a cycle would be introduced when adding (A < B), > then the thread would simply be given access to the partially-loaded > module B, by adding B to its local list of modules-being-loaded. Would it enough to (1) use recursive mutexes, and (2) have =E2=80=98resolve-module=E2=80=99 lookup modules first in the global name sp= ace, and second in the local list of modules being loaded? Thanks, Ludo=E2=80=99.