From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Eli Zaretskii Newsgroups: gmane.emacs.bugs Subject: bug#25178: 26.0.50; Crash when pressing C-g in TTY mode Date: Tue, 13 Dec 2016 21:37:27 +0200 Message-ID: <8337hrboy0.fsf@gnu.org> References: <83bmwhccib.fsf@gnu.org> <838trjbrcq.fsf@gnu.org> <878trj1vhp.fsf@linux-m68k.org> Reply-To: Eli Zaretskii NNTP-Posting-Host: blaine.gmane.org X-Trace: blaine.gmane.org 1481657958 32394 195.159.176.226 (13 Dec 2016 19:39:18 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Tue, 13 Dec 2016 19:39:18 +0000 (UTC) Cc: elias.martenson@murex.com, 25178@debbugs.gnu.org To: Andreas Schwab Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Tue Dec 13 20:39:14 2016 Return-path: Envelope-to: geb-bug-gnu-emacs@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 1cGsuv-0007Kl-Ow for geb-bug-gnu-emacs@m.gmane.org; Tue, 13 Dec 2016 20:39:13 +0100 Original-Received: from localhost ([::1]:40255 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cGsuw-0006re-Sr for geb-bug-gnu-emacs@m.gmane.org; Tue, 13 Dec 2016 14:39:14 -0500 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:57796) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cGsuo-0006rZ-Pl for bug-gnu-emacs@gnu.org; Tue, 13 Dec 2016 14:39:07 -0500 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cGsul-0002BP-Ib for bug-gnu-emacs@gnu.org; Tue, 13 Dec 2016 14:39:06 -0500 Original-Received: from debbugs.gnu.org ([208.118.235.43]:53873) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1cGsul-0002BH-En for bug-gnu-emacs@gnu.org; Tue, 13 Dec 2016 14:39:03 -0500 Original-Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.84_2) (envelope-from ) id 1cGsuj-0006XM-SD for bug-gnu-emacs@gnu.org; Tue, 13 Dec 2016 14:39:03 -0500 X-Loop: help-debbugs@gnu.org Resent-From: Eli Zaretskii Original-Sender: "Debbugs-submit" Resent-CC: bug-gnu-emacs@gnu.org Resent-Date: Tue, 13 Dec 2016 19:39:01 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: followup 25178 X-GNU-PR-Package: emacs X-GNU-PR-Keywords: Original-Received: via spool by 25178-submit@debbugs.gnu.org id=B25178.148165790025079 (code B ref 25178); Tue, 13 Dec 2016 19:39:01 +0000 Original-Received: (at 25178) by debbugs.gnu.org; 13 Dec 2016 19:38:20 +0000 Original-Received: from localhost ([127.0.0.1]:41038 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1cGsu4-0006WR-0U for submit@debbugs.gnu.org; Tue, 13 Dec 2016 14:38:20 -0500 Original-Received: from eggs.gnu.org ([208.118.235.92]:38435) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1cGsu2-0006WE-JO for 25178@debbugs.gnu.org; Tue, 13 Dec 2016 14:38:18 -0500 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cGstt-00024C-Eo for 25178@debbugs.gnu.org; Tue, 13 Dec 2016 14:38:13 -0500 Original-Received: from fencepost.gnu.org ([2001:4830:134:3::e]:50027) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cGstt-000248-BV; Tue, 13 Dec 2016 14:38:09 -0500 Original-Received: from 84.94.185.246.cable.012.net.il ([84.94.185.246]:2761 helo=home-c4e4a596f7) by fencepost.gnu.org with esmtpsa (TLS1.2:RSA_AES_256_CBC_SHA1:256) (Exim 4.82) (envelope-from ) id 1cGstq-0005rA-Eh; Tue, 13 Dec 2016 14:38:09 -0500 In-reply-to: <878trj1vhp.fsf@linux-m68k.org> (message from Andreas Schwab on Tue, 13 Dec 2016 20:26:10 +0100) 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-gnu-emacs@gnu.org List-Id: "Bug reports for GNU Emacs, the Swiss army knife of text editors" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Original-Sender: "bug-gnu-emacs" Xref: news.gmane.org gmane.emacs.bugs:127003 Archived-At: > From: Andreas Schwab > Cc: Elias Martenson , 25178@debbugs.gnu.org > Date: Tue, 13 Dec 2016 20:26:10 +0100 > > On Dez 13 2016, Eli Zaretskii wrote: > > > Hmm... Is calling pthread_mutex_unlock twice in a row, without an > > intervening call to pthread_mutex_lock, supposed to segfault? > > It's undefined, so anything can happen. Just don't do that. At this point, I'd like to establish whether the fact Emacs does do it could explain crashes reported by Elias which I cannot reproduce on a different GNU/Linux system. What I think happens is that C-g on a TTY produces a SIGINT that interrupts the call to pselect and runs handle_interrupt, which then longjmps back to read_char, which then calls thread_select. But since pselect inside the previous call to thread_select was interrupted, the following call to acquire_global_lock was not done, and we are now running with the global lock unlocked. Then thread_select calls release_global_lock which attempts to unlock the (unlocked) mutex. The question is whether this is just bad, or causes the crash. It doesn't crash for me. Thanks.