From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751262AbdFARPx (ORCPT ); Thu, 1 Jun 2017 13:15:53 -0400 Received: from out02.mta.xmission.com ([166.70.13.232]:48309 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751083AbdFARPv (ORCPT ); Thu, 1 Jun 2017 13:15:51 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: Guenter Roeck Cc: Vovo Yang , Ingo Molnar , linux-kernel@vger.kernel.org References: <20170511171108.GB15063@roeck-us.net> <87shkbfggm.fsf@xmission.com> <20170511202104.GA14720@roeck-us.net> <87y3u3axx8.fsf@xmission.com> <20170511224724.GB15676@roeck-us.net> <8760h79e22.fsf@xmission.com> <8760h66wak.fsf@xmission.com> <20170512165214.GA12960@roeck-us.net> <874lwqyo8i.fsf@xmission.com> <20170512194304.GE12960@roeck-us.net> <87wp9lvo4u.fsf@xmission.com> Date: Thu, 01 Jun 2017 12:08:58 -0500 In-Reply-To: (Guenter Roeck's message of "Sat, 13 May 2017 07:34:13 -0700") Message-ID: <87inkfab4l.fsf@xmission.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1dGThE-00023l-GO;;;mid=<87inkfab4l.fsf@xmission.com>;;;hst=in02.mta.xmission.com;;;ip=97.121.81.159;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX1/WtFPMF0VvNG8HLdbUwCCvfP4+PNaOrOs= X-SA-Exim-Connect-IP: 97.121.81.159 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * 0.0 TVD_RCVD_IP Message was received from an IP address * 0.5 XMGappySubj_01 Very gappy subject * 0.0 T_TM2_M_HEADER_IN_MSG BODY: No description available. * -0.5 BAYES_05 BODY: Bayes spam probability is 1 to 5% * [score: 0.0481] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa06 1397; Body=1 Fuz1=1 Fuz2=1] X-Spam-DCC: XMission; sa06 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;Guenter Roeck X-Spam-Relay-Country: X-Spam-Timing: total 5302 ms - load_scoreonly_sql: 0.06 (0.0%), signal_user_changed: 3.0 (0.1%), b_tie_ro: 2.0 (0.0%), parse: 0.79 (0.0%), extract_message_metadata: 11 (0.2%), get_uri_detail_list: 0.75 (0.0%), tests_pri_-1000: 8 (0.2%), tests_pri_-950: 1.50 (0.0%), tests_pri_-900: 1.17 (0.0%), tests_pri_-400: 16 (0.3%), check_bayes: 15 (0.3%), b_tokenize: 4.9 (0.1%), b_tok_get_all: 4.2 (0.1%), b_comp_prob: 1.65 (0.0%), b_tok_touch_all: 1.91 (0.0%), b_finish: 0.64 (0.0%), tests_pri_0: 99 (1.9%), check_dkim_signature: 0.57 (0.0%), check_dkim_adsp: 3.7 (0.1%), tests_pri_500: 5159 (97.3%), poll_dns_idle: 5151 (97.2%), rewrite_mail: 0.00 (0.0%) Subject: Re: Threads stuck in zap_pid_ns_processes() X-Spam-Flag: No X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Guenter Roeck writes: > > I think you nailed it. If I drop CLONE_NEWPID from the reproducer I get > a zombie process. > > I guess the only question left is if zap_pid_ns_processes() should (or could) > somehow detect that situation and return instead of waiting forever. > What do you think ? Any chance you can point me at the chromium code that is performing the ptrace? I want to conduct a review of the kernel semantics to see if the current semantics make it unnecessarily easy to get into hang situations. If the semantics make it really easy to get into a hang situation I want to see if there is anything we can do to delicately change the semantics to avoid the hangs without breaking existing userspace. We have a real problem in exec which has similar semantics and as long as I am looking at one I figure I should look at the other. Eric