From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 47688C3F2D1 for ; Mon, 2 Mar 2020 12:28:46 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 08B2A217F4 for ; Mon, 2 Mar 2020 12:28:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="VsJemNTs" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 08B2A217F4 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 822936B0006; Mon, 2 Mar 2020 07:28:45 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 7D3416B0007; Mon, 2 Mar 2020 07:28:45 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6C29C6B0008; Mon, 2 Mar 2020 07:28:45 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0059.hostedemail.com [216.40.44.59]) by kanga.kvack.org (Postfix) with ESMTP id 54B536B0006 for ; Mon, 2 Mar 2020 07:28:45 -0500 (EST) Received: from smtpin22.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 2A0A2181AC9C6 for ; Mon, 2 Mar 2020 12:28:45 +0000 (UTC) X-FDA: 76550351010.22.bag24_1226233633a38 X-HE-Tag: bag24_1226233633a38 X-Filterd-Recvd-Size: 4586 Received: from us-smtp-delivery-1.mimecast.com (us-smtp-2.mimecast.com [207.211.31.81]) by imf07.hostedemail.com (Postfix) with ESMTP for ; Mon, 2 Mar 2020 12:28:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1583152124; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=5DG/vW6TCeCX771cIMr5N8VanNi7DmSktqX7A9P5Lf4=; b=VsJemNTsTuZC8xC8GcYvGTsNDuny4AfTVE+m+JgYgUCFwjOMh2BZbr0HoOo/epysYKo11R 4cCktcYhLAMpTZKJp87jzhO6aWFvM/Tapx5mutTE9jo8CwgILyAEF3LGzhGf6dSBbV8Ljp iDxBD9K3wKFKQbDkBfGpmwwRAW0jcr8= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-359-GBOwynXFNxyRVY2vU-jPUQ-1; Mon, 02 Mar 2020 07:28:40 -0500 X-MC-Unique: GBOwynXFNxyRVY2vU-jPUQ-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 622221B2C988; Mon, 2 Mar 2020 12:28:36 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.70]) by smtp.corp.redhat.com (Postfix) with SMTP id DA8D99051B; Mon, 2 Mar 2020 12:28:29 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Mon, 2 Mar 2020 13:28:36 +0100 (CET) Date: Mon, 2 Mar 2020 13:28:29 +0100 From: Oleg Nesterov To: Bernd Edlinger Cc: Jann Horn , Christian Brauner , Jonathan Corbet , Alexander Viro , Andrew Morton , Alexey Dobriyan , "Eric W. Biederman" , Thomas Gleixner , Frederic Weisbecker , Andrei Vagin , Ingo Molnar , "Peter Zijlstra (Intel)" , Yuyang Du , David Hildenbrand , Sebastian Andrzej Siewior , Anshuman Khandual , David Howells , James Morris , Kees Cook , Greg Kroah-Hartman , Shakeel Butt , Jason Gunthorpe , Christian Kellner , Andrea Arcangeli , Aleksa Sarai , "Dmitry V. Levin" , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , "stable@vger.kernel.org" Subject: Re: [PATCHv2] exec: Fix a deadlock in ptrace Message-ID: <20200302122828.GA9769@redhat.com> References: <20200301185244.zkofjus6xtgkx4s3@wittgenstein> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 03/01, Bernd Edlinger wrote: > > This fixes a deadlock in the tracer when tracing a multi-threaded > application that calls execve while more than one thread are running. Heh. Yes, known problem. See my attempt to fix it: https://lore.kernel.org/lkml/20170213141452.GA30203@redhat.com/ > @@ -1224,7 +1224,7 @@ struct mm_struct *mm_access(struct task_struct *task, unsigned int mode) > struct mm_struct *mm; > int err; > > - err = mutex_lock_killable(&task->signal->cred_guard_mutex); > + err = mutex_lock_killable(&task->signal->cred_change_mutex); So if I understand correctly your patch doesn't fix other problems with debugger waiting for cred_guard_mutex. I too do not think this can justify the new mutex in signal_struct... Oleg.